On the action of metallic magnesium on the water of crystallization of crystal hydrates. Activation of metallic magnesium by salts
Abstract Generated abstract
This study examines the reaction of metallic magnesium with the water of crystallization in crystal hydrates and the influence of added salts on this process. After reviewing prior work on magnesium in aqueous salt solutions, the authors report experiments with numerous hydrated salts, acids, and bases, measuring hydrogen evolution and reaction onset under heating and grinding, both with and without proposed activators. The results indicate that magnesium can decompose crystallization water with hydrogen formation, that reaction intensity depends on the hydrate, and that salts such as chlorides of copper, zinc, mercury, aluminum, tin, antimony, chromium, and iron, as well as iodine, often markedly accelerate the reaction. The authors further find no comparable hydrogen evolution from anhydrous acids or bases, and defer systematic analysis of reaction products, especially in activated systems.
Full Text
Ya. I. Mikhaylenko and P. G. Moshchinskii
On the Action
of Metallic Magnesium
on the Water of Crystallization of Crystal Hydrates.
Activation of Metallic Magnesium by Salts.
Offprint from the Proceedings of the Tomsk Technological Institute of Emperor Nicholas II. Vol. 31, 1913.
Tomsk.
Steam Printing House of P. I. Orlova, Yamskoy Lane, own house.
1914.
Printed by order of the Director of the Tomsk Technological Institute of Emperor Nicholas II.
On the Action of Metallic Magnesium on the Water of Crystallization of Crystal Hydrates.
Activation of Metallic Magnesium by Salts.
Ya. I. Mikhailenko and L. T. Mushchinskago.
It was observed that powdered metallic magnesium, when mixed with certain crystal hydrates of salts, reacts vigorously with them, with the evolution of hydrogen; it was also observed that the addition of certain salts accelerates the reaction.
The investigation of this reaction—namely, the relation to metallic magnesium of the water bound to the molecule of a salt in the form of a crystal hydrate; the influence of the addition of other salts; and, finally, the investigation of the reaction products—constitutes the subject of the present work.
Since it could be supposed that the action of magnesium on crystal hydrates would be analogous to the action of magnesium on aqueous solutions, and since, on the other hand, it was important to compare the two reactions, a reference search was made in the literature on the action of magnesium on aqueous solutions of salts.
Chapter I.
The action of metallic magnesium on aqueous solutions of salts.
The action of metallic magnesium on water and on aqueous solutions of salts was the subject of the following investigations:
Roussin, Jahresbericht für Chem. u. s. w. 1866, 170.
Zeitschr. f. anal. Chem. 6, 100.
A. Comaille, Comptes rendus de l’Acad. des Sciences de Paris 63, 556.
Jahresber. f. Chem. u. s. w. 1866, 171.
Zeitschr. f. anal. Chem. 6, 101.
W. N. Hartley, Chem. News 14, 73; Wagner’s Jahresber. 1866, 7.
Kern, Chem. News 32, 309;
Jahresber. f. Chem. u. s. w. 1875, 212;
Chem. News 33, 112, 236; Jahresber. für Chem. 1876, 236.
Böttger, Chem. Centralbl., 1875, 306.
Seubert und Schmidt, Liebig’s Annalen 267, 218.
Divers, Chem. Centralbl., 1898, II, 828.
Bryant, Chem. Centralbl., 1897, II, 407.
Vitali, Chem. Centralbl., 1896, I, 14.
Lemoine, Comptes rendus de l’Acad. des Sc. de Paris 130, 140 (1899).
Tommasi, Bull. Soc. Chim. Paris [3] 21, 885, (1899).
Chem. Centralbl., 1899, II, 1094.
Jahresber. für Chem. 1899, I, 603.
Bryant, Chem. News 80, 211.
Jahresber. d. Chem. 1899, I, 602.
Bryant, Chem. News 79, 75.
Clowes und Coven, Chem. Centralbl. 1898, I, 88.
Ch. T. Roberts and L. Brown. Journ. Americ. Chem. Soc. 25, 801.
Chem. Centralbl., 1903, II, 822.
Moureour, Comptes rendus de l’Acad. des Sc. de Paris 130, 140 (1900).
Kallenberg, Journ. Amer. Chem. Soc. 25, 380 (1903).
Chem. Centralbl. 1903, I, 1249.
Frator, Pharm. Post. 38, 153 (1905).
Chem. Centralbl. 1905, I, 1305.
Combining into one whole the data of these works, which in most cases consist of fragmentary observations, we obtain the following general picture of the action of Mg on water in the presence and absence of salt-like compounds.
Stoichiometry of the reaction. Water. Metallic magnesium (at ordinary temperature) does not act on distilled water which has been freed, by boiling, from oxygen and carbon dioxide dissolved in it and then cooled in an airless space.
Metallic magnesium decomposes distilled water that has not been boiled, or that has been boiled and then saturated with oxygen or CO₂: H₂ is evolved and Mg(OH)₂ is formed (Roberts and Brown).
Ammonium salt. On an aqueous solution of NH₄Cl, metallic magnesium acts according to the equation:
\[ 2\mathrm{NH}_4\mathrm{Cl}+\mathrm{Mg}=\mathrm{MgCl}_2+\mathrm{H}_2+2\mathrm{NH}_3,\ \text{or} \]
\[ 2\mathrm{NH}_4^{\bullet}+\mathrm{Mg}=2\mathrm{NH}_3+\mathrm{Mg}^{\bullet\bullet}+\mathrm{H}_2^{*} \]
The reaction proceeds as readily as the dissolution of metallic magnesium in aqueous HCl (Seubert und Schmidt; Kern; Tommasi).
\[ \begin{aligned} &{}^{*}\ \text{Probably this reaction is accompanied also by the parallel reaction of decomposition of water:}\\ &\mathrm{Mg}+2\mathrm{H}_2\mathrm{O}=\mathrm{Mg}(\mathrm{HO})_2+\mathrm{H}_2,\ \text{or}\\ &2\mathrm{H}^{\bullet}+\mathrm{Mg}=\mathrm{H}_2+\mathrm{Mg}^{\bullet\bullet}. \end{aligned} \]
Similarly, metallic magnesium acts on aqueous solutions of the salts: \((\mathrm{NH}_4)_2\mathrm{CO}_3\), \((\mathrm{NH}_4)_2\mathrm{C}_2\mathrm{O}_4\), \((\mathrm{NH}_4)_2\mathrm{SO}_4\). Hydrogen is evolved vigorously.
An aqueous solution of \(\mathrm{NH}_4\mathrm{F}\) does not react with metallic Mg (Mouraour).
Sodium salts. With a solution of \(\mathrm{NaCl}\), metallic Mg slowly evolves hydrogen according to the equation:
\[ \mathrm{NaCl},\ n\mathrm{H}_2\mathrm{O}+\mathrm{Mg} = \mathrm{NaCl},\ (n-2)\mathrm{H}_2\mathrm{O}+\mathrm{Mg}(\mathrm{OH})_2+\mathrm{H}_2. \]
For example, with a \(1/10\) normal solution of sodium chloride and with a strip of metallic magnesium 33 cm long, at ordinary temperature, Roberts and Brown observed the evolution of the following quantities of hydrogen:
| In 1 hour — 1.7 cu. cm. | In 5 hours — 27.4 cu. cm. |
| “ 2 ” — 5.6 ” ” | “ 6 ” — 35.3 ” ” |
| “ 3 ” — 11.8 ” ” | “ 7 ” — 42.6 ” ” |
| “ 4 ” — 19.5 ” ” | “ 8 ” — 49.4 ” ” |
Energetic evolution of \(\mathrm{H}_2\) occurs under the action of metallic magnesium on solutions of \(\mathrm{Na}_2\mathrm{CO}_3\) and \(\mathrm{Na}_2\mathrm{B}_4\mathrm{O}_7\); under the action on a solution of \(\mathrm{NaC}_2\mathrm{H}_3\mathrm{O}_2\), it is fairly strong; under the action on solutions of \(\mathrm{Na}_2\mathrm{HPO}_4\), \(\mathrm{NaNO}_2\), \(\mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3\), and Seignette salt, it is very weak (Mouraour).
A solution of \(\mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3\) with a strip of Mg gives \(\mathrm{H}_2\) and \(\mathrm{Mg}(\mathrm{OH})_2\); magnesium powder in a solution of \(\mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3\) becomes colored grayish; this mass with HCl gives \(\mathrm{H}_2\mathrm{S}\) (Factor).
Potassium salts. With a solution of \(\mathrm{KCl}\), metallic Mg slowly evolves hydrogen according to the equation:
\[ \mathrm{KCl},\ n\,2\mathrm{H}_2\mathrm{O}+\mathrm{Mg} = \mathrm{KCl},\ (n-2)\mathrm{H}_2\mathrm{O}+\mathrm{Mg}(\mathrm{OH})_2+\mathrm{H}_2. \]
With a \(1/10\) normal solution of \(\mathrm{KCl}\) and with a magnesium strip 33 cm long, at ordinary temperature, Roberts and Brown observed the evolution of the following quantities of hydrogen:
| In 1 hour — 0.7 cu. cm. | In 5 hours — 25.0 cu. cm. |
| “ 2 ” — 3.5 ” ” | “ 6 ” — 33.8 ” ” |
| “ 3 ” — 9.0 ” ” | “ 7 ” — 41.6 ” ” |
| “ 4 ” — 16.6 ” ” |
Under the action of metallic Mg on a solution of \(\mathrm{K}_4\mathrm{Fe}(\mathrm{CN})_6\), hydrogen is likewise slowly evolved (Mouraour).
Calcium salts. The reaction of metallic Mg with a solution of \(\mathrm{CaCl}_2\) proceeds according to the equation:
\[ \mathrm{CaCl}_2,\ n\mathrm{H}_2\mathrm{O}+\mathrm{Mg} = \mathrm{CaCl}_2,\ (n-2)\mathrm{H}_2\mathrm{O}+\mathrm{Mg}(\mathrm{OH})_2+\mathrm{H}_2. \]
The evolution of hydrogen is weak (Mouraour). Mg does not act on a saturated solution of \(\mathrm{CaCl}_2\); on a 30% solution of \(\mathrm{CaCl}_2\) the action is stronger (Tommasi).
With a solution of CaCl₂ containing \(1/10\) gram-molecule of CaCl₂ per liter, and with a Mg ribbon 33 cm long, at ordinary temperature, Roberts and Brown observed the evolution of the following quantities of hydrogen:
| In 1 hour— | 2.2 cu. cm. | In 5 hours— | 32.1 cu. cm. |
| “ 2 “ — | 6.6 “ “ | “ 6 “ — | 41.0 “ “ |
| “ 3 “ — | 13.2 “ “ | “ 7 “ — | 48.8 “ “ |
| “ 4 “ — | 22.7 “ “ | “ 8 “ — | 56.0 “ “ |
Strontium salts. On a solution of SrCl₂ metallic Mg reacts according to the same equation as on a solution of CaCl₂. The evolution of hydrogen is very weak (Tommasi). At ordinary temperature Mg only after two days becomes covered with a layer of oxide (Kern).
With a solution of SrCl₂ containing \(1/10\) gram-molecule of SrCl₂ per liter, and with a Mg ribbon 33 cm long, at ordinary temperature, Roberts and Brown observed the evolution of the following quantities of hydrogen:
| In 1 hour— | 2.3 cu. cm. | In 5 hours— | 33.8 cu. cm. |
| “ 2 “ — | 7.0 “ “ | “ 6 “ — | 43.0 “ “ |
| “ 3 “ — | 14.3 “ “ | “ 7 “ — | 51.6 “ “ |
| “ 4 “ — | 24.1 “ “ | “ 8 “ — | 59.8 “ “ |
Barium salts. With a solution of BaCl₂ metallic Mg reacts according to the same equation as with solutions of SrCl₂ and CaCl₂.
The evolution of hydrogen is very weak (Tommasi).
With a solution of BaCl₂ containing \(1/10\) gram-molecule of BaCl₂ per liter, at ordinary temperature, Roberts and Brown observed the evolution of the following quantities of hydrogen:
| In 1 hour— | 3.02 cu. cm. | In 5 hours— | 45.5 cu. cm. |
| “ 2 “ — | 9.9 “ “ | “ 6 “ — | 55.3 “ “ |
| “ 3 “ — | 21.2 “ “ | “ 7 “ — | 64.3 “ “ |
| “ 4 “ — | 34.4 “ “ | “ 8 “ — | 72.5 “ “ |
Magnesium salts. Magnesium chloride in aqueous solution reacts with metallic Mg according to the equation:
\[ \text{a) } \mathrm{MgCl_2, nH_2O + Mg = MgCl_2 (n-2)H_2O + Mg(OH)_2 + H_2;} \]
\[ \text{b) } \mathrm{MgCl_2 + Mg(OH)_2 = 2MgCl(OH);} \]
i.e., the products of the reaction are: hydrogen, magnesium hydroxide (chiefly), and, in addition, a basic salt (a small amount).
The intensity of the reaction is approximately the same (somewhat greater) as that of the corresponding reaction with solutions of CaCl₂, SrCl₂, and BaCl₂.
Thus, with solutions containing \(^{1}/_{10}\) and \(^{3}/_{10}\) gram-molecules of \(MgCl_2\) per liter, at ordinary temperature, Roberts and Brown observed the evolution of the following quantities of hydrogen:
\(^{1}/_{10}\) gram-molecule of \(MgCl_2\) per liter:
| Time | Hydrogen evolved |
|---|---|
| After 1 hour | 3.3 cubic cm |
| After 2 hours | 11.6 cubic cm |
| After 3 hours | 24.6 cubic cm |
| After 4 hours | 37.5 cubic cm |
| After 5 hours | 48.7 cubic cm |
| After 6 hours | 59.3 cubic cm |
| After 7 hours | 69.6 cubic cm |
| After 8 hours | 78.4 cubic cm |
\(^{3}/_{10}\) gram-molecule of \(MgCl_2\) per liter:
| Time | Hydrogen evolved |
|---|---|
| After 1 hour | 3.2 cubic cm |
| After 2 hours | 13.8 cubic cm |
| After 3 hours | 29.8 cubic cm |
| After 4 hours | 42.4 cubic cm |
| After 5 hours | 54.0 cubic cm |
| After 6 hours | 64.8 cubic cm |
| After 7 hours | 74.6 cubic cm |
| After 8 hours | 83.4 cubic cm |
Analogously, Mg reacts with solutions of the salts of magnesium acetate, magnesium sulfate, and magnesium nitrate.
The reaction with solutions of \(MgSO_4\) proceeds extremely slowly (Roberts and Brown).
Zinc salts. From solutions of \(ZnCl_2\), metallic magnesium precipitates metallic zinc, \(Zn(OH)_2\), and a basic salt; in addition, hydrogen is evolved (Seubert und Schmidt; Kern; Comaille):
\[ \begin{aligned} \text{a)}\quad & ZnCl_2,\, nH_2O + Mg = ZnCl_2 (n-2)H_2O + Mg(OH)_2 + H_2;\\ \text{b)}\quad & ZnCl_2 + Mg(OH)_2 = Zn(OH)_2 + MgCl_2;\\ \text{c)}\quad & ZnCl_2 + Zn(OH)_2 = 2ZnCl(OH). \end{aligned} \]
Aqueous solutions of \(ZnSO_4\) behave similarly. The reaction proceeds vigorously (Comaille; Tommasi).
From ammoniacal solutions of \(ZnCl_2\), a mixture of the metal and hydroxide is also precipitated; however, about 20% of the ion, i.e. \(Zn(NH_3)_6^{\cdot\cdot}\), still remains in solution (Seubert und Schmidt).
Cadmium salts. On solutions of cadmium salts, the metal Mg acts analogously to its action on zinc salts. Reduction to the metal here proceeds more readily (Seubert und Schmidt; Kern; Comaille).
From ammoniacal solutions only the metal is precipitated. Only about 4% of the complex ammonium–cadmium ion remains in solution.
Mercury salts. From a neutral solution of \(HgCl_2\), metallic Mg precipitates a light-gray precipitate consisting of a mixture of \(Hg_2Cl_2\), \(Hg(OH)_2\), and metallic mercury; in addition, hydrogen is evolved (Seubert und Schmidt; Comaille; Kern; Tommasi):
a) \(\mathrm{HgCl_2},\ n\mathrm{H_2O}+\mathrm{Mg}=\mathrm{HgCl_2},\ (n-2)\mathrm{H_2O}+\mathrm{Mg(OH)_2}+\mathrm{H_2};\)
b) \(2\mathrm{HgCl_2}+\mathrm{Mg}=\mathrm{Hg_2Cl_2}+\mathrm{MgCl_2};\)
c) \(\mathrm{Hg_2Cl_2}+\mathrm{Mg}=2\mathrm{Hg}+\mathrm{MgCl_2};\)
d) \(\mathrm{HgCl_2}+\mathrm{Mg(OH)_2}=\mathrm{Hg(OH)_2}+\mathrm{MgCl_2}.\)
Calomel, suspended in water, is readily reduced to metallic mercury on boiling, and a little mercuric hydroxide is formed.
Copper salts. In a solution of \(\mathrm{CuCl_2}\), the magnesium ribbon becomes covered with a green crust of basic salt and copper hydroxide; upon more prolonged heating on a water bath, all the copper disappears from the solution, and the precipitate contains red cuprous oxide with an admixture of a greater or lesser amount of basic salt; in addition, hydrogen is evolved (Seubert und Schmidt, Comaille, Tommasi):
a) \(\mathrm{CuCl_2},\ n\mathrm{H_2O}+\mathrm{Mg}=\mathrm{CuCl_2},\ (n-2)\mathrm{H_2O}+\mathrm{Mg(OH)_2}+\mathrm{H_2};\)
b) \(2\mathrm{CuCl_2}+\mathrm{Mg}=\mathrm{Cu_2Cl_2}+\mathrm{MgCl_2};\)
c) \(2\mathrm{CuCl_2}+\mathrm{Mg(OH)_2}=2\mathrm{CuCl(OH)}+\mathrm{MgCl_2};\)
d) \(\mathrm{Cu_2Cl_2}+\mathrm{Mg(OH)_2}=\mathrm{Cu_2(OH)_2}+\mathrm{MgCl_2}.\)
A solution of \(\mathrm{CuSO_4}\), under the action of Mg, gives \(\mathrm{H_2}\), \(\mathrm{Mg(OH)_2}\), \(\mathrm{MgCl_2}\), a yellow precipitate of \(\mathrm{Cu_2(OH)_2}\), a green precipitate of basic salt, and metallic copper. The reaction proceeds vigorously. At \(0^\circ\) only \(\mathrm{Cu_2(OH)_2}\) is obtained (Tommasi). Mg acts analogously on copper acetate.
In an ammoniacal solution of \(\mathrm{CuCl_2}\), reduction of the complex cuprammonium ion proceeds to metallic copper.
The reaction proceeds very vigorously.
Silver salts. From an aqueous solution of \(\mathrm{AgNO_3}\), the metal Mg displaces metallic Ag; no hydrogen is evolved (Factor; Bryant):
\[ 2\mathrm{AgNO_3}+\mathrm{Mg}=\mathrm{Mg}''(\mathrm{NO_3})_2+2\mathrm{Ag} \]
or
\[ 2\mathrm{Ag}'+\mathrm{Mg}=\mathrm{Mg}''+2\mathrm{Ag}. \]
Metallic silver is also deposited when the metal Mg acts on an ammoniacal solution of silver nitrate (Seubert und Schmidt).
Gold salts. From a solution of \(\mathrm{AuCl_3}\), metallic Au and \(\mathrm{Mg(OH)_2}\) are precipitated; \(\mathrm{H_2}\) is evolved and \(\mathrm{MgCl_2}\) is formed (Seubert und Schmidt; Comaille; Tommasi; Factor).
Aluminum salts. From a solution of \(\mathrm{AlCl_3}\), the metal Mg displaces \(\mathrm{Al(OH)_3}\). On standing for several hours on a water bath, the precipitation is complete. At the same time the separation of a large amount of \(\mathrm{Mg(OH)_2}\) is observed (Seubert und Schmidt).
a) \(\mathrm{AlCl_3},\ n\mathrm{H_2O}+\mathrm{Mg}=\mathrm{AlCl_3},\ (n-2)\mathrm{H_2O}+\mathrm{Mg(OH)_2}+\mathrm{H_2};\)
b) \(2\mathrm{AlCl_3}+3\mathrm{Mg(OH)_2}=2\mathrm{Al(OH)_3}+3\mathrm{MgCl_2}.\)
Hydrogen is evolved vigorously (Mouraour).
Tin salts. From an aqueous solution of \(\mathrm{SnCl_4\cdot 2NH_4Cl}\), metallic Mg precipitates a hydrate of stannic acid (Seubert und Schmidt).
\[ \mathrm{SnCl_4\cdot 2NH_4Cl,\ nH_2O + Mg = SnCl_4\cdot 2NH_4Cl,\ (n-2)H_2O + Mg(OH)_2 + H_2.} \]
\[ \mathrm{SnCl_4\cdot 2NH_4Cl + 2Mg(OH)_2 = Sn(OH)_4 + 2MgCl_2 + 2NH_4Cl.} \]
Lead salts. From an aqueous solution of \(\mathrm{PbCl_2}\), at ordinary temperature, metallic Mg precipitates metallic Pb (Seubert und Schmidt); moreover, a precipitate of magnesium hydroxide and of a basic salt is formed (Comaille Tommasi):
\[ \mathrm{PbCl_2,\ nH_2O + Mg = PbCl_2,\ (n-2)H_2O + Mg(OH)_2 + H_2;} \]
\[ \mathrm{PbCl_2 + Mg = Pb + MgCl_2;} \]
\[ \mathrm{PbCl_2 + Mg(OH)_2 = Pb(OH)_2 + MgCl_2;} \]
\[ \mathrm{PbCl_2 + Pb(OH)_2 = 2Pb(OH)Cl.} \]
The evolution of \(\mathrm{H_2}\) is very vigorous (Comaille).
Metallic Mg behaves similarly toward an aqueous solution of \(\mathrm{Pb(NO_3)_2}\).
Bismuth salts. From aqueous solutions of \(\mathrm{BiCl_3}\) and \(\mathrm{Bi(NO_3)_3}\), under the action of metallic Mg, gray powdery metallic Bi is precipitated (Factor).
Chromium salts. From an aqueous solution of \(\mathrm{CrCl_3}\), in the absence of free acid, metallic Mg precipitates all the chromium in the form of the hydroxide and a basic salt:
\[ \mathrm{CrCl_3,\ nH_2O + Mg = CrCl_3,\ (n-2)H_2O + Mg(OH)_2 + H_2;} \]
\[ \mathrm{2CrCl_3 + 3Mg(OH)_2 = 2Cr(OH)_3 + 3MgCl_2;} \]
\[ \mathrm{2CrCl_3 + Mg(OH)_2 = 2CrCl_2(OH) + MgCl_2,\ etc.} \]
Hydrogen is evolved vigorously (Seubert und Schmidt; Roussin; Comaille).
The reaction proceeds similarly with solutions of chrome alum (Seubert und Schmidt).
Chromic acid salts. Potassium dichromate reacts slowly with metallic Mg; according to Kern, forming magnesium dichromate and caustic potash, but according to Factor, passing into \(\mathrm{K_2CrO_4}\).
Manganese salts. From aqueous solutions of \(\mathrm{MnCl_2}\), metallic Mg precipitates all the Mn in the form of hydroxide and a basic salt. The reaction equations are analogous to those given above for \(\mathrm{CrCl_3}\) (Seubert und Schmidt; Comaille; Rousseu; Kern).
The reaction proceeds similarly with \(\mathrm{MnSO_4}\) (Tommasi).
The reaction also proceeds in the presence of an excess of \(\mathrm{NH_4(OH)}\) and \(\mathrm{NH_4Cl}\). In this case, however, the precipitation is not complete (Seubert und Schmidt).
Salts of manganic acid. A solution of \(\mathrm{KMnO_4}\) is reduced by metallic magnesium (Factor).
Iron salts. From a solution of \(\mathrm{FeCl_3}\), metallic Mg, on heating, precipitates \(\mathrm{Fe(OH)_2}\) and a basic salt, without any admixture of metallic iron (Tommasi):
\[
\mathrm{FeCl_3 \cdot nH_2O + Mg = FeCl_3 \cdot (n-2)H_2O + Mg(OH)_2 + H_2;}
\]
\[
\mathrm{2FeCl_3 + Mg = 2FeCl_2 + MgCl_2;}
\]
\[
\mathrm{FeCl_2 + Mg(OH)_2 = Fe(OH)_2 + MgCl_2;}
\]
\[
\mathrm{2FeCl_2 + Mg(OH)_2 = 2FeCl(OH) + MgCl_2.}
\]
A solution of \(\mathrm{FeSO_4}\) with Mg gives: \(\mathrm{H_2}\), \(\mathrm{MgSO_4}\), and \(\mathrm{Fe(OH)_2}\) (Commaille; Tommasi).
Salts of cobalt. From solutions of \(\mathrm{CoCl_2}\), metallic Mg separates a precipitate of \(\mathrm{Co(OH)_2}\), basic salts, and \(\mathrm{H_2}\). No cobalt remains in solution (Tommasi).
The same reaction also proceeds in the presence of an excess of \(\mathrm{NH_4OH}\) and \(\mathrm{NH_4Cl}\). In this case, however, much cobalt salt remains in solution.
Aqueous solutions of \(\mathrm{CoSO_4}\) behave similarly toward Mg (Commaille).
Nickel salts. From solutions of \(\mathrm{NiCl_2}\), metallic Mg precipitates a mixture of nickel hydroxide and basic salt.
The same occurs in the presence of an excess of \(\mathrm{NH_4OH}\) and \(\mathrm{NH_4Cl}\).
Aqueous solutions of \(\mathrm{NiSO_4}\) behave similarly (Commaille).
Platinum salts. From solutions of \(\mathrm{PtCl_4}\), metallic Mg quantitatively precipitates metallic Pt (Seubert und Schmidt).
\(\mathrm{H_2}\) is evolved (Factor).
All the reactions just described of metallic Mg with aqueous solutions of salts may be reduced to the following two types:
1) The oxidation–reduction reaction proceeds only between metallic Mg and water. The salt acts only as a catalyst:
a) the salt, with the products of the reaction of magnesium on water, gives no insoluble compounds. The result of the reaction is the formation only of \(\mathrm{H_2}\) and \(\mathrm{Mg(OH)_2}\). For example:
\[
\mathrm{RCl \cdot nH_2O + Mg = RCl \cdot (n-2)H_2O + Mg(OH)_2 + H_2}
\quad \text{or}
\]
\[
\mathrm{2H_2O + Mg = Mg(OH)_2 + H_2,}
\quad \text{or}
\]
\[
\mathrm{2H^{\cdot} + Mg = Mg^{\cdot\cdot} + H_2.}
\]
b) the salt, with the products of the action of Mg on water, forms insoluble compounds. The result of the reaction is the formation, besides \(\mathrm{H_2}\) and \(\mathrm{Mg(OH)_2}\), of a series of basic salts and, finally, of the hydroxide of the metal of the salt. For example:
\[ \begin{aligned} &\mathrm{AlCl_3,\ nH_2O + Mg = AlCl_3,\ (n-2)H_2O + Mg(OH)_2 + H_2,}\quad \text{or}\\ &\mathrm{2H^\cdot/OH' + Mg = Mg^{\cdot\cdot}/(OH)'_2 + H_2,}\quad \text{and}\\ &\mathrm{2AlCl_3 + Mg(OH)_2 = 2AlCl_2(OH) + MgCl_2,}\\ &\mathrm{2AlCl_3 + 2Mg(OH)_2 = 2AlCl(OH)_2 + 2MgCl_2,}\\ &\mathrm{2AlCl_3 + 3Mg(OH)_2 = 2Al(OH)_3 + 3MgCl_2;} \end{aligned} \]
2) In the oxidation–reduction reaction, not only the water participates, but also the salt; i.e., two reduction reactions proceed side by side: that of the cation of the water—hydrogen—and that of the cation of the salt.
The products of both these reactions may then enter into exchange-decomposition reactions with one another and with the salt originally added:
a) the reduction of the cation does not go as far as the metal, e.g.:
\[ \begin{aligned} &\mathrm{FeCl_3,\ nH_2O + Mg = FeCl_3,\ (n-2)H_2O + Mg(OH)_2 + H_2O}\quad \text{and}\\ &\mathrm{2FeCl_3 + Mg = 2FeCl_2 + MgCl_2}\quad \text{or}\\ &\mathrm{2H^\cdot + Mg = Mg^{\cdot\cdot} + H_2,}\quad \text{and}\\ &\mathrm{2Fe^{\cdot\cdot\cdot} + Mg = 2Fe^{\cdot\cdot} + Mg^{\cdot\cdot},}\\ &\mathrm{FeCl_2 + Mg(OH)_2 = Fe(OH)_2 + MgCl_2.} \end{aligned} \]
b) The reduction of the cation of the salt goes as far as the metal, e.g.:
\[ \begin{aligned} &\mathrm{AuCl_3,\ nH_2O + Mg = AuCl_3,\ (n-2)H_2O + Mg(OH)_2 + H_2,}\quad \text{and}\\ &\mathrm{2AuCl_3 + 3Mg = Au + 3MgCl_2;}\quad \text{or}\\ &\mathrm{2H^\cdot + Mg = Mg^{\cdot\cdot} + H_2}\quad \text{and}\\ &\mathrm{2Au^{\cdot\cdot\cdot} + 3Mg = 2Au + 3Mg^{\cdot\cdot}.} \end{aligned} \]
Effect of concentration. The effect of the concentration of the salt catalyst on the course of the reaction has not been studied systematically or quantitatively.
Certain fragmentary observations apparently permit the conclusion that the rate of the reduction reaction of the water cation by the metal is approximately proportional to the concentration of the salt catalyst.
We shall illustrate these conclusions with the following table, calculated by us from Kahlenberg’s experiments.
These experiments were carried out at \(t^\circ 20^\circ\), with a piece of magnesium metal having a total surface area of 1200 sq. mm. Each experiment lasted 1–2 hours.
The table gives the quantities of hydrogen evolved in one minute.
| Salt solutions | Concentration, in gram-equivalents of salt per liter: 1/1 | Concentration, in gram-equivalents of salt per liter: 1/10 | Concentration, in gram-equivalents of salt per liter: 1/100 |
|---|---|---|---|
| $\mathrm{MgCl_2}$ | 0.35 cu. cm | 0.24 cu. cm | 0.08 cu. cm |
| $\mathrm{MgBr_2}$ | 0.15 cu. cm | 0.03 cu. cm | 0.04 cu. cm |
| $\mathrm{MgSO_4}$ | 0.22 cu. cm | 0.03 cu. cm | 0.04 cu. cm |
| $\mathrm{Mg(NO_3)_2}$*) | 0.06 cu. cm | 0.008 cu. cm | — |
| $\mathrm{H_2SO_4}$ | — | 0.9 cu. cm | 0.1 cu. cm |
| $\mathrm{HCl}$ | — | 1.0 cu. cm | 0.1 cu. cm |
The limit of the reaction, i.e., the greatest quantity of metallic magnesium capable of reacting with a given solution, was investigated only once, namely in the case of a catalyst—a magnesium salt (Lemoine).
If, for example, metallic magnesium is added little by little to a solution of $\mathrm{MgCl_2}$, then at first hydrogen is evolved and $\mathrm{Mg(OH)_2}$ is precipitated. After a more or less prolonged time the reaction stops. This, however, is due to the fact that the magnesium becomes covered with a layer of hydroxide or of basic salt, which prevents water from reaching the metal. Indeed, the filtered liquid reacts with a fresh quantity of magnesium as before. The limit of reaction, i.e., the maximum quantity of magnesium that has reacted for a given solution of a magnesium salt, is approximately proportional to the quantity of magnesium added—up to a certain limit, beyond which the amount of magnesium entering into reaction no longer increases.
The maximum quantity of magnesium entering into reaction is considerably greater than the amount present in the solution in the form of salt. For example, when a large excess of metallic Mg acts on a solution containing one gram-equivalent of $\mathrm{MgCl_2}$ salt per liter, about 47 equivalents of metallic magnesium enter into reaction.
If an excess of magnesium is allowed to act on a solution of a magnesium salt of different concentration, then the maximum quantity of metallic magnesium entering into reaction is approximately directly proportional to the dilution of the solution.
*) The reaction is accompanied by reduction of $\mathrm{NO_3'}$ to $\mathrm{NO_2'}$.
Influence of the cation and anion of the catalyst on the course of the reaction has not been systematically investigated. The factual material of isolated fragmentary observations is as follows.
With equimolecular solutions of chloride salts, the rate of hydrogen evolution corresponds to the series: $Mg^{\cdot\cdot}$, $Ba^{\cdot\cdot}$, $Sr^{\cdot\cdot}$, $Ca^{\cdot\cdot}$, $Na^{\cdot}$, $K^{\cdot}$. The following table, taken from the work of Roberts and Brown, illustrates this.
Increments of the volume of hydrogen, referred to 1 hour*):
| $1/10\ KCl$ | $1/10\ NaCl$ | $1/10\ CaCl_2$ | $1/10\ SrCl_2$ | $1/10\ BaCl_2$ | $1/10\ MgCl_2$ | |
|---|---|---|---|---|---|---|
| In 1 hour | 0.7 | 1.7 | 2.2 | 2.3 | 3.0 | 3.3 |
| » 2 » | 2.8 | 3.9 | 4.4 | 4.7 | 6.9 | 8.3 |
| » 3 » | 5.5 | 6.2 | 6.6 | 7.3 | 11.3 | 13.0 |
| » 4 » | 7.6 | 7.7 | 9.5 | 9.8 | 13.2 | 12.9 |
| » 5 » | 8.4 | 7.9 | 9.4 | 9.7 | 11.1 | 4.2 |
| » 6 » | 8.8 | 7.8 | 8.9 | 9.2 | 9.8 | 10.6 |
| » 7 » | 7.8 | 7.3 | 7.8 | 8.6 | 9.0 | 10.3 |
| » 8 » | .... | 6.8 | 7.2 | 8.2 | 8.2 | 8.8 |
The maximum rate of hydrogen evolution in more concentrated solutions is established sooner than in more dilute ones; however, the time required for completion of the reaction differs little in the two cases.
Chloride compounds react with metallic Mg considerably more vigorously than do sulfates (Roberts and Brown).
Explanation of the reaction. Lemoine, who investigated the reaction of metallic Mg on water in the presence of salts and established that magnesium salts act catalytically, explains this catalytic action by the fact that part of the magnesium salt is hydrolyzed into acid and magnesium hydroxide; the free acid reacts with the metallic magnesium. If the catalyst is $MgCl_2$, then the course of the reaction is expressed in the following way. First magnesium chloride is formed, which at the first moment is retained in solution; then it decomposes, precipitating $Mg(OH)_2$. The $MgCl_2$ thereby formed acts as though it had previously been in solution, i.e., a cycle is obtained.
Mougaour showed that the decomposition of water by metallic magnesium also occurs in the case of the presence in water of dissolved salts, such as
*) The solutions contained $1/10$ gram-molecule of the catalyst salt per liter. The magnesium ribbon was 33 cm long; the experiment lasted 8 hours at ordinary temperature.
such as NH₄Cl, (NH₄)₂SO₄, Na₂CO₃, Na₂HPO₄, NaC₂H₃O₂, KCl, BaCl₂, CaCl₂, SrCl₂, i.e., salts either not hydrolyzed at all or hydrolyzed with the formation of alkali. He finds Lemoine’s explanation inapplicable to these cases. In his opinion, it is probable that the added salts (chiefly ammonium salts) are capable of dissolving magnesium oxide, as a result of which the deposition on the surface of magnesium of a layer of hydroxide, protecting the metal from the further action of water, becomes impossible.
This explanation, he continues further, cannot, however, be applied to the cases of the action of metallic Mg on solutions of salts of heavy metals, “when, together with the separation of the heavy metal, a strong evolution of hydrogen is always observed, evidently resulting from the secondary action of Mg on the water—the solvent. In this case it is rather difficult to give an explanation of the phenomenon, since it is hardly probable that salts of Pb or Sn promote the dissolution of magnesium hydroxide.”
Comaille explains the action of metallic Mg on salts by its high electromotive force. At first, the metal of the salt is deposited on the magnesium, even if only in an insignificant amount—a galvanic couple is formed, by which the water of the solution is decomposed.
Kahlenberg points out that Lemoine’s explanation may still be accepted for solutions of salts of heavy metals, but for solutions of salts of Mg, Ca, Ba, Sr, K, Na, Li it is inapplicable, since, first, their aqueous solutions do not contain free acid, and, second, because the reaction proceeds if the solutions are made weakly alkaline. In addition, Lemoine’s explanations do not clarify why the evolution of hydrogen in a solution of MgCl₂ proceeds more vigorously than in solutions of CaCl₂, BaCl₂, SrCl₂, and why the action of metallic Mg on solutions of KCl and NaCl is very strong and, specifically, stronger on solutions of KCl than on solutions of NaCl.
In Kahlenberg’s opinion, Mouraour’s explanation is also unacceptable, since it contradicts the circumstance that, in contrast to metallic magnesium, magnesium amalgam acts extremely energetically both on solutions of NH₄F and on solutions of KOH and NaOH, with evolution of hydrogen and formation of Mg(OH)₂.
Kahlenberg regards solutions as complex composites of the dissolved substance with the solvent. Only such a point of view, in his opinion, explains why the action of Mg on salt solutions depends on the nature of the salt, and also why the degree of action of metallic Mg on solutions and the difference of potentials between magnesium and the solution proceed in parallel.
Concerning new attempts to explain the action of metallic Mg on solutions by the formation of a galvanic couple, Clowes and Coven indicate that the Cu—Mg couple prepared by them decomposes pure water very slowly.
The above review comprises all the material on the question of the action of metallic Mg on aqueous salt solutions that we were able to find in the literature. With regard to this material we consider it necessary to note the following.
Most of the works were done long ago and have the fragmentary character of isolated observations. Only the comparatively few later works aim at investigating the reaction itself; the rest pursue a stoichiometric task—the elucidation of the reaction equation in the case of various salts.
The question why the presence of salts facilitates the reaction by which magnesium passes into the ionic state must be regarded as still open.
The explanations proposed by Lemoine and by Mouraour are simple and intelligible, but can be accepted only for particular cases. Kahlenberg’s explanations are given in too general a form, are not confirmed by anything, and can be accepted only as a statement of fact.
Chapter II.
The Action of Metallic Magnesium on Salt Crystal Hydrates.
Arrangement of the experiments. A weighed amount of the crystal hydrate, ground as finely as possible, was mixed by trituration in a mortar with magnesium powder. The mixture was placed in a small flask closed with a rubber stopper, through which passed a small glass tube. The rubber connected the tube with a Woulff bottle, which played the role of a gasometer. The amount of hydrogen evolved was measured by the volume of water that flowed out of the Woulff bottle. In those cases when the reaction occurred already during mixing or trituration in the mortar, the salt powder and the magnesium were placed in the flask one after the other; the flask was closed with the stopper, connected with the gasometer, and the mixing was then carried out by shaking the small flask.
Heating was carried out: up to 100°—in a water bath; above 100°—in an air asbestos bath.
The temperature at which the reaction began was recorded. The onset of the reaction was most often expressed by a jolt (sudden evolution of hydrogen), sometimes so strong that the rubber joining the flask to the Woulff bottle came off, or the flask burst. In other cases the beginning of the reaction could be noticed by a sharp change in the rate at which the water flowed out. Often, however, the beginning of the reaction was difficult to record—the evolution of gas proceeded slowly and uniformly throughout the entire duration of the experiment.
The amount of gas evolved was not reduced to any definite temperature and pressure. It was assumed that the hydrogen was always measured at a temperature of 20° and a pressure of 750 mm. Corrections for humidity were not introduced.
The completeness of a reaction between solid bodies depends on the perfection of mixing, and even with the most thorough mixing, when the experiment is repeated, differences are obtained which far exceed the errors due to not reducing the gas volume to one and the same standard.
For the same reason all weighings were made with an accuracy of 0.02 g.
Thus, the numerical quantities obtained, by the very nature of the experiments performed, have only comparative significance and can serve only to establish an order.
Materials. We used, whenever possible, the best purified materials: from Kahlbaum—with the label “Kahlbaum,” from Merck—from the group “garantirt reine Reagentien.” The metallic magnesium was obtained from Kahlbaum. For the experiments two grades were used: “Pulver”—coarser round grains, and “Staubfein,” in the form of dust.
With both grades the reactions proceeded, in general, identically. With magnesium in the form of dust, owing to the possibility of better mixing, the completeness of the reaction was always greater.
Experimental data. Sodium salts.
Na₂CO₃ · 10H₂O + 8Mg.
Weighings: salt—1.43 g, magnesium—1 g. There was no flash. Slowly, 32 cc of hydrogen were evolved. On heating to 200°, a further 10 cc were evolved.
Of the 10 molecules of water of crystallization in the salt molecule there entered into reaction: up to 100°—0.530 mol, or 5.30%; in all—0.695, or 6.95%.
Na₂CO₃ · 10H₂O + 10Mg.
Weighings: salt—1.43 g, magnesium—1.2 g. On heating to 180° there was neither a flash nor a jolt. Hydrogen was evolved slowly: up to 100°—27 cc; up to 180°—in all 40 cc.
Of the 10 molecules of water of crystallization in the salt molecule, the following entered into reaction: up to \(100^\circ\)—0.447 mol, or 4.47%; up to \(180^\circ\) in all—0.662 mol, or 6.62%.
\(\mathrm{Na_2CO_3\cdot 10H_2O + 10Mg}\) (dust).
- The weighed portions are the same. On heating to \(100^\circ\), hydrogen was evolved slowly; there was no flash. The reaction product was a sintered mass, dark in color. 88 cc of hydrogen were collected.
Water of crystallization entered into reaction: 1.457 mol, or 14.57%.
- The weighed portions are the same. The reaction conditions are the same. 110 cc of hydrogen were collected.
Water of crystallization entered into reaction: up to \(100^\circ\)—1.821 mol, or 18.21%.
\(\mathrm{Na_2HPO_4\cdot 12H_2O + 7Mg}\).
Weighed portions: salt—3.58 g, magnesium—1.68 g. On heating there was no flash; up to \(100^\circ\), 15 cc of hydrogen were evolved uniformly; on heating to \(200^\circ\), a further 52 cc were evolved.
Water of crystallization entered into reaction: up to \(100^\circ\)—0.124 mol, or 1.03%; in all—0.557 mol, or 4.64%.
\(\mathrm{Na_2HPO_4\cdot 12H_2O + 12Mg}\) (dust).
Weighed portions: salt—1.8 g, magnesium—1.4 g. Up to \(100^\circ\), 140 cc of hydrogen were evolved. The walls were covered with drops and streaks of water. The reaction product was a gray sintered mass.
Water of crystallization entered into reaction: 2.32 mol, or 19.32%.
\(\mathrm{Na_2B_4O_7\cdot 10H_2O + 6Mg}\).
Weighed portions: salt—3.82 g, magnesium—1.4 g. The onset of hydrogen evolution occurred at about \(75^\circ\); up to \(100^\circ\), 20 cc of hydrogen were evolved uniformly; up to \(200^\circ\)—a further 20 cc. There was no flash.
Water of crystallization entered into reaction: up to \(100^\circ\)—0.165 mol, or 1.65%; in all—0.331 mol, or 3.31%.
\(\mathrm{Na_2SO_4\cdot 10H_2O + 6Mg}\).
Weighed portions: salt—3.22 g, magnesium—1.44 g. On heating there was no flash; the onset of hydrogen evolution occurred at about \(70^\circ\); up to \(100^\circ\), 32 cc of hydrogen were evolved; up to \(190^\circ\)—a further 12 cc.
Water of crystallization entered into reaction: up to \(100^\circ\)—0.26 mol, or 2.65%; up to \(190^\circ\)—0.364 mol, or 3.64%.
Na₂SO₄·10H₂O + 10Mg.
Weights: salt—3.22 g, magnesium—2.4 g. On heating to 100° there was evolved 134 cc of hydrogen. The reaction began at 50° and proceeded uniformly.
Of the water of crystallization, 1.11 mol, or 11.1%, entered into reaction.
Na₂Cr₂O₇·2H₂O + 2Mg.
Weights: salt—2.97 g, magnesium—0.5 g. On heating to 100° there was evolved 4 cc of hydrogen; up to 200°—a further 18 cc. No flashes. External appearance unchanged.
Of the water of crystallization there reacted: up to 100°—0.033 mol, or 1.66%; up to 200°—in all 0.18 mol, or 9.10%.
NaHSO₄·H₂O + Mg.
Weights: salt—2.76 g, magnesium—0.5 g. On heating to 100° there was evolved 159 cc of hydrogen; up to 200°—a further 23 cc. At 45° the mixture became caked and gas evolution began.
Of the water of crystallization that entered into reaction (if it is assumed that only the water of crystallization entered into reaction): up to 100°—0.66 mol, or 66%; up to 200°—in all 0.75 mol, or 75%.
Na₂S₂O₃·5H₂O + 3Mg.
Weights: salt—2.48 g, magnesium—0.7 g. On heating to 100° there was evolved 12 cc of hydrogen; up to 195°—a further 8 cc. No flashes.
Of the water of crystallization there entered into reaction on heating to 100°: 0.099 mol, or 1.99%; on heating to 190°—0.166 mol, or 3.31%.
Na₂SO₃·7H₂O + 4Mg.
Weights: salt—2.5 g, magnesium—1 g. On heating to 100° there was evolved 20 cc of gas; on heating to 195°—a further 20 cc. There was no swelling or flash.
Of the water of crystallization there entered into reaction on heating to 100°: 0.166 mol, or 2.36%; on heating to 195°—in all 0.331 mol, or 4.73%.
NaC₂H₃O₂·3H₂O + 2Mg.
Weights: salt—2.8 g, magnesium 1 g. On heating to 100° there was evolved 25 cc of hydrogen; up to 200°—a further 38 cc. The mixture swelled; on heating to 200° it boiled.
Of the water of crystallization there entered into reaction: up to 100°—0.103 mol, or 3.45%; up to 200° in all—0.261 mol, or 8.69%.
$\mathrm{NaC_2H_3O_2 \cdot 3H_2O + 3Mg}$.
Weights: salt—2.8 g, magnesium—1.4 g. No noticeable reaction. Slow evolution of hydrogen. Up to $100^\circ$, 30 cu. cm were collected.
Crystallization water that entered into reaction: 0.124 mol, or 4.14%.
$\mathrm{NaC_2H_3O_2 \cdot 3H_2O + 3Mg}$ (dust).
Weights the same. Slow evolution of hydrogen at about $75^\circ$. In all, upon heating to $100^\circ$, 74 cu. cm were collected.
Up to $100^\circ$, 0.31 mol of crystallization water entered into reaction, or 10.21%.
Potassium salts.
$\mathrm{K_4Fe(CN)_6 \cdot 3H_2O + 2Mg}$.
Weights: salt—4.2 g, magnesium 0.5 g. Upon heating to $100^\circ$, 4 cu. cm of hydrogen were evolved; up to $200^\circ$, another 3 cu. cm. The external appearance of the mixture did not change.
The reaction does not proceed.
Calcium salts.
$\mathrm{CaCl_2 \cdot 6H_2O + 3Mg}$.
Weights: salt—2.19 g, magnesium—0.72 g. Upon heating to $90^\circ$ the mixture melts, but no gas is evolved. Upon heating to $210^\circ$, 90 cu. cm of gas were gradually evolved.
Crystallization water that entered into reaction: up to $100^\circ$—0 mol, or 0%; upon heating to $200^\circ$—0.745 mol, or 12.42%.
$\mathrm{CaSO_4 \cdot 2H_2O + 1\frac{1}{2}Mg}$.
Weights: salt—2.44 g, magnesium 0.7 g. Upon heating to $190^\circ$, 4 cu. cm of gas were evolved. The external appearance of the mixture was unchanged.
The reaction did not proceed.
Strontium salts.
$\mathrm{SrCl_2 \cdot 6H_2O + 3Mg}$.
Weights: salt—2.66 g, magnesium—0.72 g. Upon heating to $100^\circ$ there is no reaction; upon heating to $170^\circ$, 95 cu. cm of gas were evolved, probably from water that was released by heating, condensed on the walls, and flowed back into the flask.
Crystallization water that entered into reaction: up to $100^\circ$—0 mol, or 0%; upon heating to $210^\circ$—0.786 mol, or 13.11%.
$\mathrm{SrBr_2 \cdot 6H_2O + 3Mg}$.
Weights: salt—3.55 g, magnesium 0.7 g. Upon heating to $100^\circ$, 16 cu. cm of hydrogen were evolved; upon heating to $200^\circ$, another 68 cu. cm were evolved. At $200^\circ$ the mixture fused and swelled.
Crystallization water that entered into reaction: up to $100^\circ$—0.132 mol, or 2.22%; up to $200^\circ$ in all 0.695 mol, or 11.59%.
Barium salts.
BaCl₂ · 2H₂O + Mg.
Charges: salt—2.44 g, magnesium 0.24 g. On heating to 90° no reaction occurred; on heating to 170° no reaction was noticeable. 5 cu. cm of gas was evolved.
The reaction does not proceed.
BaCl₂ · 2H₂O + 2Mg (powder).
Charges: salt—4.8 g, magnesium—1 g. On heating to 100° no gas was evolved.
The reaction did not proceed.
BaJ₂ · 2H₂O + 3Mg (powder).
Charges: salt—4.27 g, magnesium—0.5 g. No reaction was noticeable. On heating to 100°, 2 cu. cm was evolved; up to 165°, a further 9 cu. cm.
Of the water of crystallization, there entered into reaction: up to 100°—0 mol, or 0%; up to 165°—0.091 mol, or 4.55%.
Ba(OH)₂ · 8H₂O + 5Mg.
Charges: salt—3.15 g, magnesium—0.24 g. On heating to 100°, 44 cu. cm of gas was evolved; on heating to 200°, a further 9 cu. cm. At 70° vigorous mixing begins.
Of the water of crystallization entered into reaction (assuming that the water of crystallization enters into the reaction): up to 100°—0.36 mol, or 4.55%; up to 200°—in all 0.439 mol, or 5.48%.
BaO₂ · 8H₂O + 5Mg.
Charges: salt—1.6 g, magnesium—0.6 g. On heating to 200° no reaction was noticeable. In all, about 6 cu. cm of gas was evolved. The external appearance of the mixture was unchanged.
The reaction does not proceed.
Magnesium salts.
MgCl₂ · 6H₂O + 3Mg.
Charges: salt—2.03 g, magnesium 0.72 g. On heating to 100° no reaction is noticeable. Hydrogen begins to be evolved rather rapidly at 150°, while the mixture swells up and becomes gray. 86 cu. cm of hydrogen was evolved.
Of the water of crystallization entered into reaction: up to 100°—0 mol, or 0%; above 150°—0.712 mol, or 11.87%.
MgCl₂ · NH₄Cl · 6H₂O + 4Mg.
Charges: salt—2.53 g, magnesium 1 g. On heating to 200° there was an insignificant evolution of gas. The external appearance of the mixture was unchanged.
The reaction does not proceed.
MgCl₂ · NH₄Cl · 6H₂O + 7Mg (powder).
Charges: salt—2.53 g, magnesium—1.7 g. Up to 100° the reaction did not proceed; the walls were wet owing to the water evolved. The mixture was a mobile powder. 8 cu. cm of gas was evolved.
Of the water of crystallization, 0.066 mol, or 1.10%, entered into reaction.
MgBr₂ · 6H₂O + 3Mg.
Weighed portions: salt—2.92 g, magnesium—0.7 g. On heating to 100°, 22 cu. cm of hydrogen were evolved; up to 150°—a further 52 cu. cm.
Water of crystallization entered into reaction: up to 100°—0.182 mol. or 3.03%; up to 150°—in all 0.613 mol. or 10.21%.
MgSO₄ · 7H₂O + 4Mg.
Weighed portions: salt—2.46 g, magnesium—1 g. On heating to 100°, 26 cu. cm were slowly evolved. On heating to 200° (at about 160° a distinctly more rapid increase in the rate of hydrogen evolution was observed), a further 35 cu. cm were evolved.
Water of crystallization entered into reaction: up to 100°—0.215 mol. or 3.07%; up to 200°—in all 0.505 mol. or 7.21%.
MgSO₄ · 7H₂O + 7Mg (dust).
Weighed portions: salt—2.46 g, 1.7 g. On heating to 100°, 71 cu. cm of hydrogen were evolved. The reaction began at about 70°; in the middle the mixture swelled up somewhat.
Water of crystallization entered into reaction: up to 100°—0.58711 mol. or 8.40%.
Zinc salts.
ZnSO₄ · 7H₂O + 4Mg.
Weighed portions: salt—2.87 g, magnesium—1 g. On heating to 100°, hydrogen—157 cu. cm—was evolved. On heating to 200°—a further 40 cu. cm. The reaction began with a push at 60°, with swelling of the mixture.
Water of crystallization entered into reaction: up to 100°—1.300 mol. or 18.57%; up to 200°—in all 1.631 mol. or 23.3%.
ZnSO₄ · 7H₂O + 7Mg (dust).
Weighed portions: salt 2.87 g, magnesium—1.7 g. Rapid evolution of hydrogen began at 80°, the mixture swelling up. There was no push. After the reaction was over, the appearance was a dark-gray, sintered mass. Much water at the walls. Up to 100°, 100 cu. cm of hydrogen were evolved.
Water of crystallization entered into reaction: 0.829 mol. or 11.83%.
ZnCO₃ · H₂O + Mg.
Weighed portions: salt—2.87 g, magnesium—0.5 g. On heating to 195°, 8 cu. cm of hydrogen were evolved. The appearance of the mixture was unchanged.
Water of crystallization entered into reaction: up to 195°—0.033116 mol. or 3.31%.
Cadmium salts.
3CdSO₄ · 8H₂O + 4Mg.
Weighed portions: salt 3.84 g, magnesium—1 g. On heating to 100°, 16 cu. cm of hydrogen were evolved; up to 200°—a further 14 cu. cm. The appearance of the mixture did not change.
Water of crystallization entered into reaction: up to 100°—0.265 mol. or 3.31%; up to 200°—in all 0.496 mol. or 6.21%.
$$ \mathrm{CdCl_2\cdot 2H_2O + Mg.} $$
Weights: salt—2.19 g, magnesium—0.24. An energetic reaction occurs already on stirring. 2nd experiment: weights: salt—2.19 g, magnesium—0.48 g. The reaction proceeds in the same way as in the preceding case.
The water of crystallization enters into the reaction upon simple grinding of the mixture.
Copper salts.
$$ \mathrm{Cu(C_2H_3O)_2\cdot H_2O + Mg.} $$
Weights: salt—1.99 g, magnesium—0.24 g. Below \(100^\circ\) the reaction does not proceed. At about \(120^\circ\) evolution of hydrogen begins; at the edges the mixture turns brown. Water condenses in drops on the walls of the bulb.
The reaction does not proceed.
$$ \mathrm{CuCl_2\cdot 2H_2O + Mg.} $$
Weights: salt—1.70 g, magnesium—0.25 g. The reaction proceeds at ordinary temperature: in one day 14.5 cubic cm of hydrogen was evolved; in two days—22.5 cubic cm.
The water of crystallization enters into the reaction at ordinary temperature.
$$ \mathrm{CuCl_2\cdot 2H_2O + Mg.} $$
Weights: salt—1.70 g, magnesium—0.25 g. The reaction proceeds only at about \(75^\circ\). The mass became brown in color and swelled up. Up to \(100^\circ\), 14 cubic cm of hydrogen was evolved; up to \(170^\circ\)—a further 6 cubic cm.
Repeating the experiment with magnesium dust gave approximately the same results, i.e., the reaction proceeds extremely energetically; little gas is evolved.
Of the water of crystallization, 0.116 mol, or 5.80%, entered into the reaction.
$$ \mathrm{CuCl_2\cdot 2KCl\cdot 2H_2O + 2Mg.} $$
Weights: salt—3.2 g, magnesium—0.25 g. The reaction began at \(70^\circ\). The mixture acquired a brown color. Hydrogen evolved: up to \(100^\circ\)—65 cubic cm, up to \(200^\circ\)—171 cubic cm.
Of the water of crystallization, 0.538 mol, or 26.9%, entered into the reaction.
$$ \mathrm{Cu(NO_3)_2\cdot 6H_2O + 3Mg.} $$
Weights: salt—1.45 g, magnesium—0.36 g. The reaction proceeded energetically upon grinding. In a second experiment the reaction proceeded on shaking in the bulb; brown vapors of nitrogen oxides were evolved.
The reaction sets in upon shaking the powders of salt and magnesium.
$$ \mathrm{CuSO_4\cdot 5H_2O + 4Mg\ (dust).} $$
Weights: salt—1.24 g, magnesium—0.5 g. On heating to \(100^\circ\), hydrogen was collected, 3 cubic cm; up to \(175^\circ\)—a further 14 cubic cm. There is no displacement reaction.
The water of crystallization does not enter into the reaction at temperatures up to \(100^\circ\). Up to \(175^\circ\), 0.281 mol, or 5.63%, entered into the reaction.
CuSO₄ · 5H₂O + 2Mg.
Weights: salt—1.24 g, magnesium 0.24 g. No appreciable reaction. The walls of the tube are covered with drops of water, which, flowing down onto the mixture, causes a reaction at the points of contact with the magnesium. Up to 100° hydrogen collected—14 cu. cm.; up to 150°—a further 3 cu. cm.
Up to 100° the water of crystallization does not enter into the reaction.
CuSO₄ · (NH₄)₂SO₄ · 6H₂O + 4Mg.
Weights: salt—2 g, magnesium—0.5 g. By appearance no reaction is noticeable. At temperatures up to 100° hydrogen evolved 3 cu. cm.; up to 190°—a further 20 cu. cm.
At temperatures below 100° the water of crystallization does not enter into the reaction.
Aluminum salts.
K₂SO₄ · Al₂(SO₄)₃ · 24H₂O + 13Mg.
Weights: salt—3.16 g, magnesium—1.5 g. The reaction proceeded vigorously at a temperature of 80°–83°. Up to 100° hydrogen evolved 145 cu. cm.; up to 200°—a further 23 cu. cm.
Water of crystallization entered into the reaction: up to 100°—3.61 mol. or 15.0%; up to 200°—in all 4.173 mol. or 17.39%.
AlNH₄(SO₄)₂ · 12H₂O + 6Mg.
Weights: salt—1.12 g, magnesium—0.38 g. By appearance no reaction is noticeable. On heating to 100° hydrogen evolved 20 cu. cm.
Very little water of crystallization enters into the reaction up to 100°.
Al₂(SO₄)₃ · 18H₂O + 10Mg.
Weights: salt—3.33 g, magnesium—1.2 g. Swelling began at 160°. On heating to 200° hydrogen evolved 70 cu. cm.
Water of crystallization entered into the reaction: up to 100°—0; up to 200°—in all 1.16 mol. or 6.44%.
AlCl₃ · 6H₂O + 3Mg (dust).
Weights: salt—1.20 g, magnesium—0.36 g. No reaction is noticeable. Up to 100° hydrogen evolved 6 cu. cm.; up to 175°—a further 18 cu. cm.
Water of crystallization entered into the reaction: up to 100°—0.099 mol. or 1.66%; up to 175°—in all 0.397 mol. or 6.62%.
Tin salts.
SnCl₂ · 2H₂O + Mg.
A vigorous reaction occurs when the salt comes into contact with magnesium.
SnCl₄ · 3H₂O + Mg.
Weights: salt—3.14 g, magnesium—0.24 g. The reaction begins at 50°. Hydrogen evolved 30 cu. cm.
Water of crystallization entered into the reaction: 0.248 mol. or 8.28%.
Lead salts.
\[ \mathrm{Pb(C_2H_3O_2)_2 \cdot 3H_2O + Mg.} \]
Charges: salt—3.79 g, magnesium—0.24 g. The reaction began at \(46^\circ\). The mass swelled and turned black. About 16 cu. cm of hydrogen was evolved.
Assuming that the gas evolved was hydrogen, crystallization water entered into the reaction: 0.132 mol, or 4.42%.
Chromium salts.
\[ \mathrm{CrCl_3 \cdot 6H_2O + 3Mg.} \]
Charges: salt—2.64 g, magnesium—0.63 g. The reaction began at \(80^\circ\). The whole mass swelled. At temperatures up to \(100^\circ\), 153 cu. cm of hydrogen was evolved.
Crystallization water entered into the reaction: 1.267 mol, or 21.11%.
\[ \mathrm{CrCl_3 \cdot 6H_2O + Mg.} \]
Charges: salt—2.64 g, magnesium—0.22 g. The reaction began at \(78^\circ\); the mass swelled; the reaction proceeded calmly. Up to \(100^\circ\), 97 cu. cm of hydrogen was evolved.
Crystallization water entered into the reaction: 0.803 mol, or 13.4%.
\[ \mathrm{CrCl_3 \cdot 6H_2O + 5Mg.} \]
Charges: salt—2.64 g, magnesium—0.9 g. The reaction began at \(79^\circ\); the mass swelled; the reaction proceeded calmly. At temperatures up to \(100^\circ\), 141 cu. cm of hydrogen was evolved.
Crystallization water entered into the reaction: 1.167 mol, or 19.46%.
\[ \mathrm{K_2SO_4 \cdot Cr_2(SO_4)_3 \cdot 24H_2O + 13Mg.} \]
Charges: salt—2.50 g, magnesium—0.6 g. At \(60^\circ\)–\(65^\circ\) strong swelling occurs. At temperatures up to \(100^\circ\), 98 cu. cm of hydrogen was evolved; up to \(200^\circ\)—another 16 cu. cm.
Crystallization water entered into the reaction: up to \(100^\circ\)—3.245 mol, or 13.52%; up to \(200^\circ\)—3.775 mol, or 15.73%.
Manganese salts.
\[ \mathrm{MnCl_2 \cdot 4H_2O + Mg.} \]
Charges: salt—1.98 g, magnesium—0.24 g. The reaction began at a temperature of \(35^\circ\)–\(37^\circ\). At temperatures up to \(100^\circ\), 155 cu. cm of hydrogen was evolved.
Crystallization water entered into the reaction: 1.01 mol, or 25.25%.
\[ \mathrm{MnCl_2 \cdot 4H_2O + 3Mg.} \]
Charges: salt—1.98 g, magnesium—0.72 g. The reaction began at \(34^\circ\); it proceeded vigorously, but without a jolt. Up to \(100^\circ\), 155 cu. cm of hydrogen was evolved.
Crystallization water entered into the reaction: 1.283245 mol, or 32.08%.
$\mathrm{MnCl_2\cdot 4H_2O + 5Mg}$.
Charges: salt—1.98 g, magnesium—1.21 g. The reaction took place at \(35^\circ\)—\(37^\circ\). Up to \(100^\circ\), 216 cubic cm of hydrogen was evolved.
Crystallization water entered into reaction: 1.7883 mol, or 44.71%.
$\mathrm{MnSO_4\cdot 7H_2O + 4Mg}$.
Charges: salt—2.77 g, magnesium—1 g. In outward appearance the reaction was not noticeable. Up to \(100^\circ\), 86 cubic cm of hydrogen was evolved; up to \(200^\circ\)—a further 18 cubic cm.
Crystallization water entered into reaction: up to \(100^\circ\)—0.711 mol, or 10.16%; up to \(200^\circ\)—in all 0.861 mol, or 12.3%.
Iron salts.
$\mathrm{FeCl_3\cdot 6H_2O + Mg}$.
Charges: salt—2 g, magnesium—0.18 g. A vigorous reaction occurs already upon mixing.
The crystallization water entered into reaction at ordinary temperature.
$\mathrm{FeCl_3\cdot 6H_2O + 4Mg}$.
Charges: salt—2.63 g, magnesium—0.71 g. A vigorous reaction occurred when the magnesium powder came into contact with the salt; the salt was partly scattered; it was not possible to mix the two substances well; 80 cubic cm of hydrogen was evolved.
Crystallization water entered into reaction: 0.662 mol, or 11.04% (the reaction proceeded incompletely, owing to the impossibility of mixing).
$\mathrm{FeCl_2\cdot 4H_2O + Mg}$.
Charges: salt—2 g, magnesium—0.24 g. The reaction begins upon grinding. The mixing was carried out by shaking in a flask; the reaction began at \(45^\circ\). 90 cubic cm of hydrogen was collected.
Crystallization water reacted: 0.745 mol, or 18.63%.
$\mathrm{FeCl_2\cdot 4H_2O + 3Mg}$.
Charges: salt—2 g, magnesium—0.72 g. The mixing was carried out by shaking; the reaction began at \(37^\circ\). 132 cubic cm of hydrogen were collected.
Crystallization water entered into reaction: 1.093 mol, or 27.32%.
$\mathrm{FeCl_2\cdot 4H_2O + 2Mg}$.
Charges: salt—2 g, magnesium—0.48 g. The reaction began at \(40^\circ\). 138 cubic cm of hydrogen was evolved.
Crystallization water entered into reaction: 1.143 mol, or 28.56%.
$\mathrm{FeSO_4\cdot 7H_2O + 3Mg}$.
Charges: salt—2.78 g, magnesium—0.72 g. The reaction was imperceptible upon heating to \(150^\circ\). Hydrogen, probably owing to the fact that the mixture was wetted by drops of crystallization water that condensed on the walls and ran down onto the mixture, was evolved in the amount of 38 cubic cm.
The water of crystallization does not enter into the reaction at a temperature below \(100^\circ\).
\[ \mathrm{NH_4Fe(SO_4)_2 \cdot 12H_2O + 6Mg.} \]
Charges: salt—1.2 g, magnesium—0.38 g. The mixture reacted when ground in a mortar; the reacted mass was black in color; the smell of ammonia was perceptible.
\[ \mathrm{FeSO_4 \cdot (NH_4)_2SO_4 \cdot 6H_2O + 4Mg.} \]
Charges: salt—3.92 g, magnesium—1 g. On heating to \(100^\circ\) the mixture turned brown; 24 cu. cm of hydrogen was evolved. On heating to \(200^\circ\) the mixture became gray—another 35 cu. cm of hydrogen was evolved.
Water of crystallization entered into the reaction: up to \(100^\circ\)—0.198 mol, or 3.31%; up to \(200^\circ\)—0.488 mol, or 8.14%.
Nickel salts.
\[ \mathrm{NiCl_2 \cdot 6H_2O + 3Mg.} \]
Charges: salt—1.18 g, magnesium—0.31 g. The reaction begins at \(30^\circ\)—\(40^\circ\). At a temperature up to \(100^\circ\), 81 cu. cm of hydrogen was evolved.
Water of crystallization entered into the reaction: 1.341 mol, or 22.35%.
\[ \mathrm{NiCl_2 \cdot 6H_2O + 5Mg.} \]
First experiment. Charges: salt—1.18 g, magnesium—0.48 g. Since on grinding the mixture a reaction occurs, the mixing was carried out by shaking. The reaction began at \(37^\circ\)—\(38^\circ\). At a temperature up to \(100^\circ\), 117 cu. cm of hydrogen was evolved.
Water of crystallization entered into the reaction: 1.937 mol, or 32.29%.
Second experiment. The experiment was repeated with the same quantities. It proceeded in the same way as the preceding one. 128 cu. cm of hydrogen was evolved.
Water of crystallization entered into the reaction: 2.119 mol, or 35.32%.
\[ \mathrm{NiCl_2 \cdot 6H_2O + 7Mg.} \]
First experiment. Charges: salt—1.18 g, magnesium—0.68 g. The mixture was prepared by shaking the powders of salt and magnesium. The reaction proceeded at a temperature of \(36^\circ\)—\(38^\circ\). 120 cu. cm of hydrogen was collected.
Water of crystallization entered into the reaction: 1.987 mol, or 33.12%.
Second experiment. The experiment was repeated with the same quantities. It proceeded as did the preceding one. Gas evolved at a temperature up to \(100^\circ\)—137 cu. cm.
Water of crystallization entered into the reaction: 2.268 mol, or 37.81%.
\[ \mathrm{NiCl_2 \cdot 6H_2O + 7Mg.} \]
Charges: salt—1.18 g, magnesium—0.68 g. The apparatus with the mixture was left standing at ordinary temperature. 60 cu. cm of hydrogen was evolved.
Water of crystallization entered into the reaction: 0.993 mol, or 16.56%.
NiSO₄ · 7H₂O + 4Mg.
Weights: salt—2.8 g, magnesium—1 g. On heating to 100°, the reaction did not proceed noticeably. 14 cu. cm of hydrogen was evolved. On heating to 200°, a further 18 cu. cm of hydrogen was evolved.
Crystallization water entered into reaction: up to 100°—0.116 mol, or 1.66%.
NH₄Cl · NiCl₂ · 6H₂O + 3Mg.
Weights: salt—1.45 g, magnesium—0.36 g. The reaction began at about 50°. Hydrogen evolved up to 100°—69 cu. cm; up to 175°—a further 5 cu. cm.
Crystallization water entered into reaction: up to 100°—1.142 mol, or 19.04%.
NH₄Cl · NiCl₂ · 6H₂O + 7Mg (dust).
Weights: salt—2.9 g, magnesium—1.7 g. The reaction began below 60°. 132 cu. cm of hydrogen was evolved. The inside of the flask was covered with drops of condensed water.
Crystallization water entered into reaction: 1.093 mol, or 18.21%.
Cobalt salts.
CoCl₂ · 6H₂O + Mg.
Weights: salt—2.38 g, magnesium—0.21 g. The reaction began at about 35°. The reaction proceeds with strong heating. The whole mass turns blue and boils. Up to 100°, 64 cu. cm of hydrogen was evolved.
Crystallization water entered into reaction: 0.530 mol, or 8.86%.
CoCl₂ · 6H₂O + 3Mg.
Weights: salt—1.19 g, magnesium—0.3 g. The reaction began with a flash at 25°—30°. At temperatures up to 100°, 142 cu. cm of hydrogen was collected.
Crystallization water entered into reaction: 2.351 mol, or 39.19%.
CoCl₂ · 6H₂O + 7Mg.
Weights: salt—0.59 g, magnesium—0.35 g. At about 30° there was a very vigorous reaction, with flashes (in four experiments, where larger quantities were taken, the rubber connecting the flask with the gasometer was torn off), with a noticeable appearance of white smoke. Up to 100°, 38 cu. cm of hydrogen was evolved.
Crystallization water entered into reaction: 1.258 mol, or 20.97%.
CoSO₄ · 6H₂O + 7Mg.
Weights: salt—1.4 g, magnesium—0.48 g. There was no noticeable reaction. Up to 100°, 12 cu. cm of hydrogen was evolved; up to 200°—a further 22 cu. cm.
Crystallization water entered into reaction: up to 100°—1.987 mol, or 2.84%.
Results. The experimental material presented above, showing in general that the crystallization water of crystalline hydrates is activated with respect to magnesium, at the same time makes it possible to draw several conclu-
...the conclusions concerning the course of the reaction itself and the influence of temperature and the nature of the salt on the intensity of the reaction. These conclusions we formulate as follows.
Influence of mass. Under the given experimental conditions there can be no question of chemical mass, since the reaction takes place between solid bodies. A greater or lesser quantity of the substances entering into the reaction depends only on the greater or lesser surface of contact. Therefore the degree of pulverization and the degree of perfection of drying, as well as the ratio between the molecules of the reacting bodies, influence the yield. The following table illustrates these influences.
TABLE 1.
| Composition of the mixture. | Temperature of the beginning of the reaction. | Quantity of water of crystallization which entered into the reaction, per 100 g: molecules | Quantity of water of crystallization which entered into the reaction, per 100 g: % |
|---|---|---|---|
| $\mathrm{CrCl_3\cdot 6H_2O + Mg}$ | $78^\circ$ | 0.803 | 13.40 |
| » $\,+3\mathrm{Mg}$ | $80^\circ$ | 1.267 | 21.11 |
| » $\,+5\mathrm{Mg}$ | $79^\circ$ | 1.167 | 19.45 |
| $\mathrm{MnCl_2\cdot 4H_2O + Mg}$ | $35^\circ$—$37^\circ$ | 1.010 | 25.25 |
| » $\,+3\mathrm{Mg}$ | $34^\circ$ | 1.283 | 32.08 |
| » $\,+5\mathrm{Mg}$ | $35^\circ$—$37^\circ$ | 1.788 | 44.71 |
| $\mathrm{FeCl_2\cdot 4H_2O + Mg}$ | $45^\circ$ | 0.745 | 18.63 |
| » $\,+2\mathrm{Mg}$ | $40^\circ$ | 1.143 | 28.56 |
| » $\,+3\mathrm{Mg}$ | $40^\circ$ | 1.093 | 27.32 |
| $\mathrm{NiCl_2\cdot 6H_2O + 3Mg}$ | $38^\circ$—$40^\circ$ | 1.340 | 22.33 |
| » $\,+5\mathrm{Mg}$ | $37^\circ$—$38^\circ$ | 1.937 | 32.29 |
| » $\,+5\mathrm{Mg}$ | $37^\circ$—$38^\circ$ | 2.119 | 35.32 |
| » $\,+7\mathrm{Mg}$ | $36^\circ$—$38^\circ$ | 1.987 | 33.12 |
| » $\,+7\mathrm{Mg}$ | $36^\circ$—$38^\circ$ | 2.268 | 37.81 |
| $\mathrm{CoCl_2\cdot 6H_2O + Mg}$ | $35^\circ$ | 0.530 | 8.86 |
| » $\,+3\mathrm{Mg}$ | $25^\circ$—$30^\circ$ | 2.351 | 39.19 |
| » $\,+7\mathrm{Mg}$ | $30^\circ$ | 1.258 | 20.97 |
| $\mathrm{Na_2SO_4\cdot 10H_2O + 6Mg}$ | $70^\circ$ | 0.265 | 2.65 |
| » $\,+10\mathrm{Mg}$ | $50^\circ$ | 1.109 | 11.09 |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 2Mg}$ | 0.103 | 3.45 | |
| » $\,+3\mathrm{Mg}$ | 0.124 | 4.14 | |
| » $\,+3\mathrm{Mg}$ (dust) | 0.310 | 10.21 | |
| $\mathrm{Na_2CO_3\cdot 10H_2O + 8Mg}$ | 0.530 | 5.30 | |
| » $\,+10\mathrm{Mg}$ | 0.447 | 4.47 | |
| » $\,+10\mathrm{Mg}$ (dust) | 1.821 | 18.21 |
Thus, the better the reacting substances are ground, the greater the quantity of crystallohydrate that, other conditions being equal, can be brought into the reaction—this is clearly illustrated by parallel experiments with magnesium in the form of a coarse powder and in the form of dust.
Two parallel experiments with mixtures of identical composition, other conditions being equal, generally give results differing greatly from one another. This occurs because there is no means of controlling the degree of mixing. Hence it is clear that all quantitative measurements of the reaction can have only a conditional significance.
By increasing the quantity of magnesium, we increase the surface of contact and, therefore, the quantity of crystallohydrate that enters into the reaction increases with an increase in the relative quantity of magnesium, but only up to a certain limit.
However great the excess of magnesium may be, we have never succeeded in bringing all the water of the crystallohydrate into the reaction. On the contrary, only a comparatively small part of the water of crystallization enters into the reaction. Thus, for the crystallohydrate $\mathrm{CrCl_3\cdot 6H_2O}$ it is possible to bring into the reaction a maximum of 1.267 mol. of water; for the crystallohydrate $\mathrm{MnCl_2\cdot 4H_2O}$—a maximum of 1.788 mol. of water, etc.
The reason why it is not possible to bring all the water of the crystallohydrate into the reaction probably lies in the fact that not all molecules of the crystallohydrate are equally active with respect to magnesium, just as they do not all have the same dissociation elasticity.
To decide this question quite definitely, one should prepare crystallohydrates of one and the same salt with different water contents and test their behavior toward magnesium.
The temperature at which the reaction begins, as should have been expected, does not depend on the relative composition of the mixture.
Influence of the nature of the salt. The influence of the nature of the salt on the activity of the water of the crystallohydrate, or else on the activity of magnesium, appears very sharply. In some cases the reaction takes place upon simple mixing; in other cases upon slight heating; in still others it does not take place even upon heating to $200^\circ$. In these latter cases the water of crystallization condenses on the cold walls, flows back in streams onto the mixture, and still there is no reaction.
In order to trace the influence of the nature of the anion and cation of the salt crystallohydrate on its reaction with magnesium, we shall present the experimental data in the form of tables, compiled so that it would be possible to compare the behavior toward magnesium of different crystallohydrates with one and the same anion and different cations, and conversely—with one and the same cation and different anions.
TABLE 2.
Halide salts.
| Composition of the mixture. | Temperature at the beginning of the reaction. | Amount of water of crystallization that had entered into reaction up to 100°: Molecules | Amount of water of crystallization that had entered into reaction up to 100°: % |
|---|---|---|---|
| $\mathrm{SnCl_2\cdot 2H_2O + Mg}$ | On mixing; | could not collect hydrogen | |
| $\mathrm{FeCl_3\cdot 6H_2O + Mg}$ | On mixing; | could not collect hydrogen | |
| $\mathrm{FeCl_3\cdot 6H_2O + 4Mg}$ | On mixing | 0.662 | 11.03 |
| $\mathrm{CuCl_2\cdot 2H_2O + Mg}$ | On grinding; | could not collect hydrogen | |
| $\mathrm{CoCl_2\cdot 6H_2O + 7Mg}$ | 30° | 1.258 | 20.97 |
| $\mathrm{MnCl_2\cdot 4H_2O + 3Mg}$ | 34°—35° | 1.283 | 32.08 |
| $\mathrm{NiCl_2\cdot 6H_2O + 7Mg}$ | 36°—38° | 1.987 | 33.11 |
| $\mathrm{FeCl_2\cdot 4H_2O + 3Mg}$ | 37° | 1.093 | 27.32 |
| $\mathrm{Pb(C_2H_3O_2)_2\cdot 3H_2O + Mg}$ | 46° | 0.132 | 4.41 |
| $\mathrm{SnCl_4\cdot 3H_2O + Mg}$ | 50° | 0.248 | 8.28 |
| $\mathrm{CrCl_3\cdot 6H_2O + 5Mg}$ | 79° | 1.167 | 19.46 |
| $\mathrm{AlCl_3\cdot 6H_2O + 3Mg}$ (dust) | 0.099 | 1.66 | |
| $\mathrm{MgCl_2\cdot 6H_2O + 3Mg}$ | 0.745 | 12.42 | |
| $\mathrm{CaCl_2\cdot 6H_2O + 3Mg}$ | 0 | 0 | |
| $\mathrm{SrCl_2\cdot 6H_2O + 3Mg}$ | 0 | 0 | |
| $\mathrm{BaCl_2\cdot 2H_2O + Mg}$ | 0 | 0 | |
| $\mathrm{MgBr_2\cdot 6H_2O + 5Mg}$ | 0.182 | 3.03 | |
| $\mathrm{SrBr_2\cdot 6H_2O + 3Mg}$ | 0.132 | 2.22 | |
| $\mathrm{BaJ_2\cdot 2H_2O + 3Mg}$ (dust) | 0 | 0 |
As is evident from the data given in Tables 2—4, the halide and ferrocyanide salts provided the most extensive material for determining the series of influence of the cation. Salts with other anions either crystallize without water or are difficult to obtain.
Comparing the data obtained for the series of chloride salts, it is easy to establish the following series of cations: the most active with respect to magnesium are the crystallohydrates of stannous chloride and the metals of Group VIII of Mendeleev’s periodic system (Fe, Co, Ni); then the so-called heavy metals (Pb, Mn, Zn, Cu, Sn); less active are the salts of sodium, and still less—the group of alkaline-earth metals (Ba, Sr, Ca).
The influence of the salt anion is also very sharply manifested. For this it is enough to compare the behavior toward magnesium of chlorides and sulfates of the same metals. In all cases without exception, the group \(SO_4\) greatly lowers the activity of the crystallohydrate. Thus, for example, \(CuCl_2\cdot 2H_2O\), \(CdCl_2\cdot 2H_2O\), \(NiCl_2\cdot 2H_2O\), \(MnCl_2\cdot 2H_2O\), etc., react energetically with magnesium, while the corresponding sulfates (\(CdSO_4\cdot 7H_2O\), \(NiSO_4\cdot 7H_2O\), \(MnSO_4\cdot 7H_2O\), etc.) either react very weakly or do not react at all (\(CuSO_4\cdot 5H_2O\)).
Double sulfates and alums react more energetically than sulfates in general (Table 3).
TABLE 3.
Sulfates.
| Nature of the crystallohydrate and composition of the mixture | Temperature at which reaction begins | Amount of water of crystallization that entered into reaction up to \(100^\circ\), molecules | Amount of water of crystallization that entered into reaction up to \(100^\circ\), % |
|---|---|---|---|
| \(Na_2SO_4\cdot 10H_2O + 10Mg\) | \(50^\circ\) | 1.109 | 11.09 |
| \(ZnSO_4\cdot 7H_2O + 4Mg\) | \(60^\circ\) | 1.300 | 18.57 |
| \(MnSO_4\cdot 7H_2O + 4Mg\) | When heated to \(100^\circ\) | 0.702 | 10.16 |
| \(CoSO_4\cdot 6H_2O + 7Mg\) | — | 1.987 | 2.84 |
| \(NiSO_4\cdot 7H_2O + 4Mg\) | — | 0.116 | 1.65 |
| \(3CuSO_4\cdot 8H_2O + 4Mg\) | — | 0.265 | 3.31 |
| \(CuSO_4\cdot 5H_2O + 4Mg\) (dust) | — | 0 | 0 |
| » » \(+ 2Mg\) | — | 0 | 0 |
| \(Al_2(SO_4)_3\cdot 18H_2O + 10Mg\) | — | 0 | 0 |
| \(Fe(NH_4)_2(SO_4)_2\cdot 6H_2O + 4Mg\) | — | 0.199 | 3.31 |
| \((NH_4)_2SO_4\cdot Fe_2(SO_4)_3\cdot 24H_2O + 12Mg\) | On mixing | hydrogen could not be collected | hydrogen could not be collected |
| \(K_2SO_4\cdot Cr_2(SO_4)_3\cdot 24H_2O + 13Mg\) | \(60^\circ\) | 3.245 | 13.52 |
| \(K_2SO_4\cdot Al_2(SO_4)_3\cdot 24H_2O + 13Mg\) | \(80^\circ\)—\(83^\circ\) | 3.600 | 15.07 |
| \((NH_4)_2SO_4\cdot Al_2(SO_4)_3\cdot 24H_2O + 12Mg\) | When heated to \(100^\circ\) | reaction does not proceed | reaction does not proceed |
The influence of other anions cannot be elucidated for lack of material. Thus, apparently, hydrates of halide salts possess the greatest activity, and among them the hydrates \(SnCl_2\cdot 2H_2O\) and \(FeCl_3\cdot 6H_2O\) are distinguished by exceptional activity.
TABLE 4.
Salts of other acids.
| Nature of the crystallohydrate and composition of the mixture | Temperature at the beginning of the reaction | Amount of water of crystallization that entered into reaction up to 100°, molecules | Amount of water of crystallization that entered into reaction up to 100°, % |
|---|---|---|---|
| $\mathrm{Pb(C_2H_3O_2)_2\cdot 3H_2O + Mg}$ | $46^\circ$ | 0.132 | 4.41 |
| $\mathrm{Na(C_2H_3O_2)\cdot 3H_2O + 3Mg}$ (filings) | $75^\circ$ | 0.31 | 10.21 |
| same $\mathrm{+2Mg}$ | On heating to $100^\circ$ | 0.103 | 3.45 |
| $\mathrm{Na_2CO_3\cdot 10H_2O + 8Mg}$ | On heating to $100^\circ$ | 0.530 | 5.30 |
| same $\mathrm{+10Mg}$ (filings) | — | 1.457 | 14.57 |
| $\mathrm{Na_2SO_3\cdot 7H_2O + 4Mg}$ | On heating to $100^\circ$ | 0.166 | 2.36 |
| $\mathrm{Na_2S_2O_3\cdot 5H_2O + 3Mg}$ | On heating to $100^\circ$ | 0.100 | 1.99 |
| $\mathrm{Na_2B_4O_7\cdot 10H_2O + 6Mg}$ | $75^\circ$ | 0.165 | 1.65 |
| $\mathrm{Na_2Cr_2O_7\cdot 2H_2O + 2Mg}$ | On heating to $100^\circ$ | 0.033 | 1.65 |
| $\mathrm{Na_2HPO_4\cdot 12H_2O + 7Mg}$ | On heating to $100^\circ$ | 0.124 | 1.03 |
| same $\mathrm{+12Mg}$ (filings) | — | 2.32 | 19.32 |
Action of metallic magnesium on solid bases and acids
In discussing the cause of the activity of crystallohydrates with respect to magnesium, one may arrive at the supposition that a solid crystallohydrate may be regarded as a single molecule containing hydroxyls, and that it is precisely the hydroxyls of this molecule which enter into reaction with magnesium.
In order to obtain experimental material that could serve for an assessment of this supposition, the following experiments were also carried out with bases and acids crystallizing with water of crystallization and without it.
Bases.
\[ \mathrm{3NaOH + 1\tfrac{1}{2}Mg.} \]
Weights: $\mathrm{NaOH}$—3 g, magnesium—0.9 g. Flashes are seen on heating to $200^\circ$. Hydrogen collected: up to $100^\circ$—26 cubic cm, in all 48 cubic cm.
Up to $100^\circ$, 2.87% of hydrogen entered into reaction; in all, 5.29%.
\[ \mathrm{2KOH + 2Mg.} \]
Weights: $\mathrm{KOH}$—1.12 g, magnesium—0.48 g.
In an air bath, at a temperature somewhat above $100^\circ$, there was a strong explosion.
\[ \mathrm{Ca(OH)_2 + Mg.} \]
Weights: $\mathrm{Ca(OH)_2}$—1.48 g, magnesium—0.48 g.
The reaction did not proceed on heating to $200^\circ$.
Pb(OH)\(_2\) + 2Mg.
Charges: Pb(OH)\(_2\)—2.41 g, magnesium—0.48 g.
The reaction did not proceed on heating to 200°.
Al\(_2\)(OH)\(_6\) + 4Mg.
Charges: Al\(_2\)(OH)\(_6\)—1.56 g, magnesium—0.96 g.
The reaction did not proceed on heating to 200°.
Ba(OH)\(_2\) · 8H\(_2\)O + 5Mg.
First experiment. Charges: Ba(OH)\(_2\) · 8H\(_2\)O—3.15 g, magnesium—1.20 g. On heating to 190°, 73 cu. cm of hydrogen was evolved.
Of the crystallization water, 0.604 mol, or 7.55%, entered into the reaction.
Second experiment. The charges were the same. Swelling of the mixture began at about 70°. On heating to 100°, 44 cu. cm of hydrogen was evolved; on heating to 200°, a further 9 cu. cm.
On heating to 100°, 0.364 mol, or 4.55%, of the crystallization water entered into the reaction.
Peroxide. BaO\(_2\) · 8H\(_2\)O + 6Mg.
Charges: BaO\(_2\) · 8H\(_2\)O—1.6 g, magnesium—0.72 g. The mixture was heated to 200°.
The reaction did not proceed.
Acids. 2H\(_3\)BO\(_3\) + 3Mg.
Charges: acid—1.24 g, magnesium—0.72 g.
The reaction was noticeable on heating to 160°.
HSbO\(_3\) + 2Mg.
Charges: acid—1.69 g, magnesium—0.48 g.
The reaction did not proceed on heating to 200°.
H\(_3\)PO\(_4\) + 2Mg.
Charges: acid—0.98 g, magnesium—0.48 g.
The reaction did not proceed on heating to 200°.
C\(_6\)H\(_5\)·CH : CH.CO\(_2\)H + Mg (Pulver).
Charges: acid—1.48 g, magnesium—0.24 g.
The reaction did not proceed.
H\(_3\)AsO\(_4\) · 1/2H\(_2\)O + 1/2Mg.
First experiment. Charges: acid—1.51 g, magnesium—0.12 g. About 11 cu. cm of hydrogen was collected. Second experiment. Charges: acid 3 g, magnesium—0.24 g. Slow evolution of hydrogen was observed between 65° and 95°. On heating to 200°, 27 cu. cm of hydrogen was collected.
Assuming that the crystallization water enters into the reaction, 0.101 mol of crystallization water, or 20.28%, reacted (average of the two experiments).
$$ \mathrm{C_2O_4H_2\cdot 2H_2O}\ \text{(oxalic acid)} + 4\mathrm{Mg}. $$
Weighed portions: acid—1.26 g, magnesium—0.96 g. On heating to \(100^\circ\) the mixture becomes compacted. No visible reaction is observed. Gas evolved: 32 cubic cm. On heating to \(200^\circ\), a further 22 cubic cm of gas evolved.
Assuming that the water of crystallization enters into the reaction, the following reacted: up to \(100^\circ\)—0.263 mol of water of crystallization, or 13.25%; up to \(200^\circ\)—in all 0.447 mol, or 22.35%.
$$ \mathrm{C_3H_4(OH)(CO_2H)_3\cdot H_2O}\ \text{(citric acid)} + 3\mathrm{Mg}. $$
Weighed portions: acid—2.1 g, magnesium—0.72 g. On heating to \(100^\circ\) no visible reaction is observed. 41 cubic cm of gas was collected. On heating to \(200^\circ\), a further 43 cubic cm of gas evolved.
Assuming that the water of crystallization enters into the reaction, the following reacted: up to \(100^\circ\)—0.339 mol of water of crystallization, or 33.94%; up to \(200^\circ\) in all—0.695 mol, or 69.54%.
$$ \mathrm{C_6H_2(OH)_3CO_2H\cdot H_2O}\ \text{(pyrogallic acid)} + 2\tfrac{1}{2}\mathrm{Mg}. $$
Weighed portions: acid—1.88 g, magnesium—0.60 g. On heating to \(200^\circ\), 14 cubic cm of gas was collected.
Assuming that the water of crystallization enters into the reaction, 0.116 mol of water of crystallization reacted, or 11.59%.
Acid salt. \(\mathrm{KHSO_4} + \mathrm{Mg}\).
Weighed portions: salt—2.72 g, magnesium—0.48 g.
The reaction did not proceed on heating to \(200^\circ\).
$$ \mathrm{NaHSO_4}\ \text{(fused)} + \mathrm{Mg}. $$
Weighed portions: salt—2.76 g, magnesium—0.48 g.
There was no reaction on heating to \(200^\circ\).
$$ \mathrm{NaHCO_3} + \mathrm{Mg}. $$
Weighed portions: salt—1.68 g, magnesium—0.48 g.
The reaction did not proceed.
$$ \mathrm{NHF_4\cdot HF} + \mathrm{Mg}. $$
Weighed portions: salt—1.14 g, magnesium—0.48 g. On heating to \(100^\circ\) there is no reaction. Sintering of the mixture began at about \(170^\circ\). About 54 cubic cm of hydrogen evolved.
0.2235 mol of salt, or 22.35%, entered into the reaction.
$$ \mathrm{NaHSO_4\cdot H_2O} + \mathrm{Mg}. $$
Weighed portions: salt—2.76 g, magnesium—0.48 g. Sintering began at \(45^\circ\). Up to \(100^\circ\), 159 cubic cm of hydrogen evolved; up to \(200^\circ\), in all 182 cubic cm.
Assuming that only the water of crystallization entered into the reaction, the following reacted: on heating to \(100^\circ\)—0.658 mol, or 65.8%; on heating to \(200^\circ\)—in all 0.753 mol of salt, or 75.3%.
Results. The experiments just described may be summarized as follows:
- Hydroxides which do not contain water of crystallization in their molecule: $\mathrm{Ca(OH)_2}$, $\mathrm{Pb(OH)_2}$, $\mathrm{Al(OH)_3}$, do not react with magnesium when heated to $200^\circ$.
Barium hydroxide reacts weakly with magnesium, with a small evolution of hydrogen; caustic potash—unexpectedly—reacts to an extremely energetic degree. The latter reaction, however, had already been investigated by Winkler, and he found that the reaction here proceeds not according to the type studied in the present work.
-
Barium hydroxide and barium peroxide, crystallizing with water of crystallization, react with magnesium.
-
Anhydrous acids and acid salts: $\mathrm{H_3BO_3}$, $\mathrm{HSbO_3}$, $\mathrm{H_3PO_4}$, $\mathrm{KHSO_4}$, $\mathrm{NaHSO_4}$, $\mathrm{NaHCO_3}$, $\mathrm{C_6H_5.CH:CH.CO_2H}$ do not react with magnesium. The exception is $\mathrm{NH_4F \cdot HF}$.
-
Acids and acid salts crystallizing with water of crystallization: $\mathrm{H_3AsO_4 \cdot \tfrac{1}{2}H_2O}$, $\mathrm{H_2C_2O_4 \cdot 2H_2O}$, $\mathrm{C_6H_2(OH)_3.CO_2H \cdot H_2O}$, $\mathrm{C_3H_4(OH)(CO_2H)_3 \cdot H_2O}$ all react with magnesium, and to approximately the same extent as other crystalline hydrates.
Conclusion. Thus, the constitutional water of bases and acids is not active with respect to magnesium. Hydrate water, however, of both acids and bases is active and, moreover, to approximately the same degree as the hydrate water of salts.
To the question posed above—whether a crystalline hydrate is something analogous to an acid—the experiments given above therefore provide a negative answer.
By contrast, a comparison of the action of magnesium on crystalline hydrates and on aqueous salt solutions will provide a basis for drawing an analogy between water bound to a molecule according to the type of a crystalline hydrate and water bound according to the type of a solution.
Chapter III.
Activation of the Reaction of Magnesium with the Water of Crystallization of Crystalline Hydrates.
The above investigation of the reactions of magnesium with crystalline hydrates, which showed the influence of the nature of the anion and cation of the salt on the energy of the reaction, led to the idea of activating this reaction.
For this purpose, a crystalline hydrate was chosen whose salt nature exerted little activating influence on the reaction of its water of crystallization with magnesium, and then the addition of various—
... on the course of this reaction. The arrangement of the experiments is, in general, the same as in those described earlier. Heating was carried out to \(100^\circ\).
All the salts used as activators were taken in an entirely dry state, without water of crystallization. To one molecule of the crystalline hydrate, one molecule of activator was usually added. The experimental material obtained is given below.
Experimental material. The object of the experiments was the reaction
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg}. \]
Metallic magnesium was taken in the form of powder.
The reaction \(\mathrm{MgSO_4\cdot 7H_2O + 7Mg}\), in the absence of foreign salts, begins at \(70^\circ\). Upon heating to \(100^\circ\), \(0.587\) mol of water of crystallization enters into the reaction, or \(8.40\%\).
The added salts, whose activating effect on the reaction was studied, are arranged in the order of the groups of the periodic system. Cu, Ag, and Au are assigned to the eighth group.
Salts of potassium and sodium.
\[ \mathbf{MgSO_4\cdot 7H_2O + 7Mg + KCl.} \]
Weights: salt—2.46 g, magnesium—1.7 g, KCl—0.8 g. The mixture was heated to \(100^\circ\). The reaction is imperceptible. \(40\) cubic cm of hydrogen was collected.
Of the 7 molecules of the crystalline hydrate, \(0.331\) mol of water of crystallization reacted, or \(4.73\%\).
Potassium chloride does not activate. The same applies to sodium chloride.
Salts of calcium.
\[ \mathbf{MgSO_4\cdot 7H_2O + 7Mg + CaCl_2.} \]
Weights: salt—2.46 g, magnesium—1.7 g, \(\mathrm{CaCl_2}\)—1.1 g. Very slow evolution of hydrogen. Upon heating to \(100^\circ\), \(33\) cubic cm of hydrogen was collected.
Water of crystallization that entered into the reaction: \(0.273\) mol, or \(3.90\%\).
\(\mathrm{CaCl_2}\) does not activate.
\[ \mathbf{MgSO_4\cdot 7H_2O + 7Mg + CaBr_2.} \]
Weights: salt—2.46 g, magnesium—1.7 g, \(\mathrm{CaBr_2}\)—2.0 g. The reaction began at about \(80^\circ\). \(118\) cubic cm of hydrogen was collected. The mixture swelled up.
\(0.97\) mol, or \(13.95\%\), of water of crystallization entered into the reaction.
\(\mathrm{CaBr_2}\) activates weakly.
Salts of barium.
\[ \mathbf{MgSO_4\cdot 7H_2O + 7Mg + BaCl_2.} \]
Weights: salt—2.46 g, magnesium—1.7 g, \(\mathrm{BaCl_2}\)—2.08 g. There is no appreciable reaction. \(40\) cubic cm of hydrogen was evolved.
Entered into reaction: 0.331 mol of water of crystallization, or 4.73%.
$\mathrm{BaCl_2}$ does not activate.
Salts of magnesium.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + MgCl_2}. \]
Charges: salt—2.46 g, magnesium—1.7 g, $\mathrm{MgCl_2}$—1.0 g. Slow evolution begins at $90^\circ$. 70 cu. cm collected. The external appearance of the mixture did not change.
Entered into reaction: 0.579 mol of water of crystallization, or 8.28%.
$\mathrm{MgCl_2}$, if it does exert an activating influence, then only a very weak one.
Salts of zinc.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + ZnCl_2}. \]
Charges: salt—2.46 g, magnesium—1.7 g, $\mathrm{ZnCl_2}$—1.4 g. The reaction began with a pop at $50^\circ$. 170 cu. cm of hydrogen were collected. In view of the small amount of water in the gasometer, heating was discontinued at $60^\circ$.
Up to $60^\circ$, the following entered into reaction: 1.407 mol of water of crystallization, or 20.11%.
$\mathrm{ZnCl_2}$ activates.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + ZnCO_3\cdot H_2O}. \]
Charges: salt—2.46 g, magnesium—1.7 g, $\mathrm{ZnCO_3\cdot H_2O}$—1.4 g. The reaction is imperceptible. 34 cu. cm of hydrogen were collected.
Entered into reaction: 0.281486 mol of water of crystallization, or 4.02%.
$\mathrm{ZnCO_3\cdot H_2O}$ does not activate.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + ZnSO_4}. \]
Charges: salt—2.46 g, magnesium—1.7 g, $\mathrm{ZnSO_4}$—1.6 g. The reaction is imperceptible. 34 cu. cm of hydrogen were collected.
Entered into reaction: 0.281 mol of water of crystallization, or 4.02%.
$\mathrm{ZnSO_4}$ does not activate.
Salts of cadmium.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + CdCl_2}. \]
Charges: salt—2.46 g, magnesium—1.7 g, $\mathrm{CdCl_2}$—1.8 g. The reaction began at $80^\circ$. There was no flash or pop. The reacting mass swelled somewhat. Hydrogen evolved: 186 cu. cm.
Entered into reaction: 1.54 mol of water of crystallization, or 22.00%.
$\mathrm{CdCl_2}$ activates.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + CdSO_4.} \]
Weights: salt—2.46 g, magnesium—1.7 g, CdSO₄—2 g. The reaction did not proceed. CdSO₄ does not activate.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + CdCO_3.} \]
Weights: salt—2.46 g, magnesium—1.7 g, CdCO₃—1.7 g. No reaction was noticed. Hydrogen collected: 38 cu. cm.
Crystallization water that entered into reaction: 0.315 mol, or 4.49%.
CdCO₃ does not activate.
Mercury salts.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + HgCl_2.} \]
First experiment. Weights: salt—2.46 g, magnesium—1.7 g, HgCl₂—2.7 g. The reaction began already upon grinding the mixture in a mortar.
Second experiment. The weights were the same. Mixing was carried out by shaking the flask. The reaction began with a jolt at 45°. Immediately 100 cu. cm of hydrogen was evolved; upon further heating, another 73 cu. cm. Product of the reaction—a caked mass.
Crystallization water that entered into reaction: 1.432 mol of crystallization water, or 20.46%.
HgCl₂ activates.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + \tfrac{1}{2}Hg_2Cl_2.} \]
Weights: salt—2.46 g, magnesium—1.7 g, Hg₂Cl₂—2.3 g. No reaction was noticed. Hydrogen collected: 30 cu. cm.
Crystallization water that entered into reaction: 0.248 mol, or 3.55%.
Hg₂Cl₂ does not activate.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + HgSO_4.} \]
Weights: salt—2.46 g, magnesium—1.7 g, HgSO₄—3.0 g. The reaction did not proceed. The external appearance of the mixture did not change. Hydrogen evolved: 16 cu. cm.
Crystallization water that entered into reaction: 0.132 mol, or 1.89%.
HgSO₄ acts as if in a retarding manner.
Aluminum salts.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + AlCl_3.} \]
Weights: salt—2.46 g, magnesium—1.7 g, AlCl₃—1.3 g. The reaction proceeded very vigorously at ordinary temperature. Hydrogen evolved: 184 cu. cm.
Crystallization water that entered into reaction: 1.523 mol, or 21.76%.
AlCl₃ activates.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + K_2SO_4\cdot Al_2(SO_4)_3.} \]
Weights: salt—2.46 g, magnesium—1.7 g, alum—5.0 g. The reaction was not noticeable. Hydrogen collected: 11 cu. cm.
Crystallization water entered into reaction: 0.091 mol., or 1.30%.
\(\mathrm{K_2SO_4\cdot Al_2(SO_4)_3}\) acts, as it were, in a retarding manner.
Salts of tin.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + SnCl_2.} \]
Weights: salt—2.46 g, magnesium—1.7 g, \(\mathrm{SnCl_2}\)—1.9 g. The reaction proceeded with a strong push at \(35^\circ\). Upon heating to \(100^\circ\), a total of 223 cu. cm of hydrogen was evolved.
Crystallization water entered into reaction: 1.846 mol., or 26.37%.
\(\mathrm{SnCl_2}\) activates vigorously.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + SnI_2.} \]
Weights: salt—2.46 g, magnesium—1.7 g, \(\mathrm{SnI_2}\)—3.7 g. The reaction proceeded with a strong explosion. The flask burst.
\(\mathrm{SnI_2}\) activates vigorously.
Salts of lead.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + \tfrac{1}{2}PbCl_2.} \]
Weights: salt—2.46 g, magnesium—1.7 g, \(\mathrm{PbCl_2}\)—1.3 g. The reaction began at about \(80^\circ\). Hydrogen evolved: 80 cu. cm.
Crystallization water entered into reaction: 0.662 mol., or 9.46%.
\(\mathrm{PbCl_2}\) does not activate.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + PbO.} \]
Weights: salt—2.46 g, magnesium—1.7 g, \(\mathrm{PbO}\)—2.2 g. A fairly rapid evolution of gas at about \(60^\circ\), which soon ceased. 48 cu. cm of hydrogen were collected.
Crystallization water entered into reaction: 0.397 mol., or 5.68%.
\(\mathrm{PbO}\) does not activate.
Salts of antimony.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + SbCl_3.} \]
First experiment. Weights: salt—2.46 g, magnesium—1.7 g, \(\mathrm{SbCl_3}\)—2.25 g. The reaction proceeded at ordinary temperature upon shaking the flask with the mixture.
Second experiment. The weights were the same. The mixture was prepared by pouring one powder into the flask after the other. The reaction proceeded only at \(25^\circ\). The mixture was then heated to \(100^\circ\). Hydrogen evolved: 108 cu. cm.
Entered into reaction of water of crystallization: 0.894 mol, or 12.77%.
\(\mathrm{SbCl_3}\) activates vigorously.
\[ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + Sb_2O_5}. \]
Weighed portions: salt—2.46 g, magnesium—1.7 g, \(\mathrm{Sb_2O_5}\)—3.3 g. The reaction was not noticeable. Hydrogen collected: 26 cu. cm.
Entered into reaction of water of crystallization: 0.215 mol, or 3.08%.
\(\mathrm{Sb_2O_5}\) acts as if in a retarding manner.
\[ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + Sb_2S_5}. \]
Weighed portions: salt—2.46 g, magnesium—1.7 g, \(\mathrm{Sb_2S_5}\)—4 g. The reaction was not noticeable. 30 cu. cm of gas was evolved.
Entered into reaction of water of crystallization: 0.248 mol, or 3.55%.
\(\mathrm{Sb_2S_5}\) does not activate.
Chromium salts.
\[ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + CrCl_3}. \]
Weighed portions: salt—2.46 g, magnesium—1.7 g, \(\mathrm{CrCl_3}\)—1.6 g. The reaction proceeded with a strong jolt at \(30^\circ\). The mixture ignited. In all, 143 cu. cm of hydrogen was evolved.
Entered into reaction of water of crystallization: 1.189 mol, or 16.98%.
\(\mathrm{CrCl_3}\) activates vigorously.
\[ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + CrFl_3}. \]
Weighed portions: salt—2.46 g, magnesium—1.7 g, \(\mathrm{CrFl_3}\)—1.0 g. The reaction was not noticeable. Hydrogen collected: 30 cu. cm.
Entered into reaction of water of crystallization: 0.247 mol, or 3.55%.
\(\mathrm{CrFl_3}\) does not activate.
Manganese salts.
\[ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + MnCl_2}. \]
Weighed portions: salt—2.46 g, magnesium—1.7 g, \(\mathrm{MnCl_2}\)—1.3 g. The reaction began at \(75^\circ\). There was no flash. Hydrogen evolved: 200 cu. cm.
Entered into reaction of water of crystallization: 1.656 mol, or 23.65%.
\(\mathrm{MnCl_2}\) activates.
Iodine.
\[ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + \tfrac{1}{2} I_2}. \]
First experiment. Weighed portions: salt—2.46 g, magnesium—1.7 g, iodine—1.3 g. A vigorous reaction occurred already while the mixture was being ground in a mortar.
Second experiment. The same weighed portions. A vigorous reaction occurred when the flask with the mixture was shaken. It was not possible to mix the powders well. 140 cu. cm of hydrogen was evolved during the flash.
Entered into reaction of water of crystallization: 1.159 mol, or 16.56%.
$\mathrm{J_2}$ activates energetically.
Iodoform.
$$ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + CHJ_3.} $$
Charges: salt—2.46 g, magnesium—1.7 g, iodoform—4 g. The reaction proceeded slowly, beginning at \(70^\circ\). There was no flash. About 200 cu. cm of gas was evolved. External appearance of the reaction product: a densely sintered mass. On the walls of the flask were drops of a dark-red heavy liquid, evidently \(\mathrm{CH_2J_2}\); only an odor of \(\mathrm{CH_2J_2}\), the odor of iodoform disappeared.
Entered into reaction of water of crystallization (if the evolved gas is counted as hydrogen): 1.656 mol, or 23.65%.
Iodoform activates energetically.
Iron salts.
$$ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + FeCl_3.} $$
First experiment. Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{FeCl_3}\)—1.6 g. The reaction proceeded at \(30^\circ\) with a strong jolt, tearing the rubber from the apparatus. The amount of hydrogen was not determined. The reaction product was a mass of layered structure.
Second experiment. Charges the same. The reaction proceeded with a jolt at \(45^\circ\). Immediately 140 cu. cm of hydrogen was evolved; with further heating—another 33 cu. cm.
Entered into reaction of water of crystallization: 1.846 mol, or 26.37%.
\(\mathrm{FeCl_3}\) activates energetically.
$$ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + Fe_2(SO_4)_3 \cdot (NH_4)_2SO_4.} $$
Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{Fe_2(SO_4)_3 \cdot (NH_4)_2SO_4}\)—5 g. There was no jolt. 104 cu. cm of hydrogen was evolved.
Entered into reaction of water of crystallization: 0.861 mol, or 12.30%.
\(\mathrm{Fe_2(SO_4)_3 \cdot (NH_4)_2SO_4}\) activates weakly (does not activate).
$$ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + Fe_2O_3.} $$
Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{Fe_2O_3}\)—1.6 g. There was no flash. The external appearance did not change. 44 cu. cm of hydrogen was evolved.
Entered into reaction of water of crystallization: 0.364 mol, or 5.20%.
\(\mathrm{Fe_2O_3}\) does not activate.
Cobalt salts.
$$ \mathrm{MgSO_4 \cdot 7H_2O + 7Mg + CoCl_2.} $$
Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{CoCl_2}\)—1.3 g. The reaction proceeded at \(60^\circ\), with 208 cu. cm of hydrogen being evolved.
No further heating was carried out.
Crystallization water entered into reaction: 1.722 mol, or 24.60%.
\(\mathrm{CoCl_2}\) activates vigorously.
Nickel salts.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + NiCl_2}. \]
Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{NiCl_2}\)—1.3 g. 122 cubic cm of hydrogen were evolved.
Crystallization water entered into reaction: 1.010 mol, or 14.43%.
\(\mathrm{NiCl_2}\) activates.
Copper salts.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + CuCl_2}. \]
Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{CuCl_2}\)—1.3 g. The reaction proceeded with a flash at \(25^\circ\). In all, 282 cubic cm of hydrogen were evolved.
Crystallization water entered into reaction: 2.335 mol, or 33.35%.
\(\mathrm{CuCl_2}\) activates vigorously.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + Cu_2Cl_2}. \]
Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{Cu_2Cl_2}\)—2 g. The reaction proceeded with a push at \(30^\circ\). 80 cubic cm of hydrogen were evolved, and upon further heating another 24 cubic cm.
Crystallization water entered into reaction: 1.441 mol, or 20.58%.
\(\mathrm{Cu_2Cl_2}\) activates vigorously.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + CuBr_2}. \]
Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{CuBr_2}\)—2.2 g. The reaction proceeded with a push at \(70^\circ\). In all, 236 cubic cm of hydrogen were evolved.
Crystallization water entered into reaction: 1.954 mol, or 27.91%.
\(\mathrm{CuBr_2}\) activates vigorously.
\[ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + Cu_2J_2}. \]
Charges: salt—2.46 g, magnesium—1.7 g, \(\mathrm{Cu_2J_2}\)—3.8 g. A slow evolution of gas was noticeable from the beginning of the experiment. A more vigorous reaction occurred at about \(80^\circ\). 247 cubic cm of hydrogen were collected.
Crystallization water entered into reaction: 2.045 mol, or 29.21%.
\(\mathrm{Cu_2J_2}\) activates vigorously.
$$ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + CuSO_4.} $$
Charges: salt—2.46 g, magnesium—1.7 g, $\mathrm{CuSO_4}$—1.6 g. There was no noticeable reaction in the form of a flash. Hydrogen evolved: 20 cu. cm. The reaction product was a dark-brown caking mass.
Crystallization water entered into reaction: 0.166 mol, or 2.37%.
$\mathrm{CuSO_4}$ exerts, as it were, a retarding action.
$$ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + CuCO_3.} $$
Charges: salt—2.46 g, magnesium—1.7 g, $\mathrm{CuCO_3}$—1.2 g. The evolution of hydrogen began at about $70^\circ$, but soon stopped. In all, 50 cu. cm were collected.
Crystallization water entered into reaction: 0.414 mol, or 5.91%.
$\mathrm{CuCO_3}$ does not activate.
$$ \mathrm{MgSO_4\cdot 7H_2O + 7Mg + CuO.} $$
Charges: salt—2.46 g, magnesium—1.7 g, $\mathrm{CuO}$—1.0 g. There was neither a jolt nor a flash. The outward appearance of the mixture changed little. Hydrogen collected: 82 cu. cm.
Crystallization water entered into reaction: 0.67 mol, or 9.68%.
$\mathrm{CuO}$ activates weakly.
Results. The experimental data given above may be summarized as follows.
-
The reaction of magnesium with the crystallization water of the crystallohydrate $\mathrm{MgSO_4\cdot 7H_2O}$ is activated by the addition of certain substances. In a whole series of individual cases, this activating influence is manifested very sharply.
-
The substances that activate the reaction—we shall call them activators—are, in general, those same substances which activate while present in the molecule of the crystallohydrate.
For a better survey of the substances that proved to be activators, and for comparison of their activating influence, they are collected in Table 5, p. 42.
For the substances brought together in Table 5, their activating action is evident; in the majority of cases it is even manifested very sharply. Thus, in the absence of an activator, the reaction of magnesium with the crystallization water of $\mathrm{MgSO_4\cdot 7H_2O}$ begins only at $70^\circ$, and upon heating to $100^\circ$ only about 0.6 mol, or 8.4%, of the crystallization water enters into reaction. In the presence of $\mathrm{CuCl_2}$, however, the reaction begins already at $25^\circ$ in the form of a flash or jolt, and 2.335 mol, or 33.35%, of the crystallization water enters into reaction; in the presence of $\mathrm{FeCl_3}$, $\mathrm{HgCl_2}$, $\mathrm{AlCl_3}$, etc., the reaction begins already during grinding in a mortar—in this case the mixture has to be prepared in a flask, by mixing
TABLE 5.
| Reaction: \( \mathrm{MgSO_4\cdot 7H_2O + 7Mg}\) (dust) + activator | Temperature at the beginning of the reaction | Molecules | % |
|---|---|---|---|
| \(\mathrm{MgSO_4\cdot 7H_2O + 7Mg}\) | \(70^\circ\) | 0.587 | 8.40 |
| \(\mathrm{MgSO_4\cdot 7H_2O + 7Mg + ZnCl_2}\) | \(50^\circ\) | 1.407 | 20.11 |
| \(\mathrm{+ CdCl_2}\) | \(80^\circ\) | 1.540 | 22.00 |
| \(\mathrm{+ HgCl_2}\) | upon grinding | 1.432 | 20.46 |
| \(\mathrm{+ AlCl_3}\) | upon grinding | 1.523 | 21.76 |
| \(\mathrm{+ SnCl_2}\) | upon grinding | 1.846 | 26.37 |
| \(\mathrm{+ SnJ_2}\) | explosion | not measured | not measured |
| \(\mathrm{+ SbCl_3}\) | upon grinding | 0.894 | 12.77 |
| \(\mathrm{+ CrCl_3}\) | strong push | 1.189 | 16.98 |
| \(\mathrm{+ MnCl_2}\) | \(75^\circ\) | 1.656 | 23.65 |
| \(\mathrm{+ J_2}\) | upon grinding | 1.159 | 16.56 |
| \(\mathrm{+ CHJ_3}\) | \(70^\circ\) | 1.656 | 23.65 |
| \(\mathrm{+ FeCl_3}\) | upon grinding | 1.846 | 26.37 |
| \(\mathrm{+ CoCl_2}\) | \(60^\circ\) | 1.722 | 24.60 |
| \(\mathrm{+ NiCl_2}\) | \(60^\circ\) | 1.010 | 14.42 |
| \(\mathrm{+ CuCl_2}\) | shaking at \(25^\circ\) | 2.335 | 33.35 |
| \(\mathrm{+ Cu_2Cl_2}\) | push at \(30^\circ\) | 1.440 | 20.57 |
| \(\mathrm{+ CuBr_2}\) | push at \(70^\circ\) | 1.954 | 27.91 |
| \(\mathrm{+ Cu_2J_2}\) | at ordinary temperature | 2.045 | 29.21 |
the substances by cautious shaking;*) finally, in the presence of \(\mathrm{SnJ_2}\), the reaction occurs in the form of a strong explosion with only a contact mixing of the crystallohydrate and the activator with magnesium.
In the following table 6 are listed those substances which either do not exert a noticeable influence on the reaction of magnesium with the water of crystallization of the crystallohydrate, or act as if in a retarding manner.
As is evident from the cited table 6, the following do not activate: potassium chloride, alkali-metal chlorides, including magnesium chloride; carbonic-acid and sulfuric-acid salts and oxides of heavy metals: zinc, cadmium, mercury and copper; i.e., they do not acti-
*) In this way, of course, it is not possible to mix the substances well; moreover, the reaction often occurs at the very beginning of mixing, before the substances have even been mixed at all adequately. This explains the circumstance that the amount of hydrogen evolved often does not correspond to the intensity of the reaction.
TABLE 6.
| Reaction: $\mathrm{MgSO_4\cdot 7H_2O + 7Mg}$ (powder) + activators: |
Temperature of the start of the reaction | Amount of water of crystallization entering into the reaction up to $100^\circ$: molecules |
Amount of water of crystallization entering into the reaction up to $100^\circ$: % |
|---|---|---|---|
| $\mathrm{MgSO_4\cdot 7H_2O + 7Mg}$ | $70^\circ$ | 0.587 | 8.40 |
| $\mathrm{MgSO_4\cdot 7H_2O + 7Mg + KCl}$ | not observed | 0.331 | 4.73 |
| » » $\mathrm{+CaCl_2}$ | » | 0.273 | 3.90 |
| » » $\mathrm{+CaBr_2}$ | $80^\circ$ | 0.977 | 13.95 |
| » » $\mathrm{+BaCl_2}$ | not observed | 0.331 | 4.73 |
| » » $\mathrm{+MgCl_2}$ | » | 0.572 | 8.28 |
| » » $\mathrm{+ZnCO_3}$ | » | 0.281 | 4.02 |
| » » $\mathrm{+ZnSO_4}$ | » | 0.281 | 4.02 |
| » » $\mathrm{+CdCO_3}$ | » | 0.315 | 4.49 |
| » » $\mathrm{+Hg_2Cl_2}$ | » | 0.248 | 3.55 |
| » » $\mathrm{+HgSO_4}$ | » | 0.132 | 1.89 |
| » » $\mathrm{+KAl(SO_4)_2}$ | » | 0.091 | 1.30 |
| » » $\mathrm{+PbCl_2}$ | $80^\circ$ | 0.662 | 9.46 |
| » » $\mathrm{+PbO}$ | $60^\circ$ | 0.397 | 5.68 |
| » » $\mathrm{+Sb_2O_5}$ | not observed | 0.215 | 3.07 |
| » » $\mathrm{+Sb_2S_5}$ | » | 0.248 | 3.55 |
| » » $\mathrm{+Fe_2O_3}$ | » | 0.364 | 5.20 |
| » » $\mathrm{+CuSO_4}$ | » | 0.165 | 2.36 |
| » » $\mathrm{+CuCO_3}$ | » | 0.413 | 5.91 |
| » » $\mathrm{+CuO}$ | » | 0.670 | 9.60 |
give the same salts whose crystallohydrates do not react with magnesium.
The retarding influence of the electronegative group $\mathrm{SO_4}$ is manifested here just as sharply as before. Thus, $\mathrm{CuCl_2}$ and $\mathrm{HgCl_2}$ are energetic activators (see Table 5), whereas $\mathrm{HgSO_4}$ and $\mathrm{CuSO_4}$ not only do not activate, but even act in a retarding manner.
Here one can also establish an analogous action of the group $\mathrm{CO_3}^{*}$ and of divalent oxygen. Indeed, $\mathrm{ZnCO_3}$, $\mathrm{CdCO_3}$, $\mathrm{CuCO_3}$, $\mathrm{Sb_2O_5}$, $\mathrm{Fe_2O_3}$, and $\mathrm{CuO}$ behave either indifferently or as retarders of the reaction.
*) It was not possible to obtain this earlier, since the carbonic-acid salts rarely contain water of crystallization.
Verification of the action of activators. In order to elucidate the cause and mechanism of the action of activators, the solution of the question was of importance: is the action of the activators found accidental or constant? In other words, are the substances cited above capable of activating the reaction of magnesium with the water of crystallization of all other crystalline hydrates in the same way as they activate the reaction of magnesium with the crystalline hydrate $MgSO_4 \cdot 7H_2O$, or not? To resolve this question, experiments were carried out on the activation, by various activators, of the reaction of magnesium with crystalline hydrates: $NaC_2H_3O_2 \cdot 3H_2O$, $CaCl_2 \cdot 6H_2O$, $CuSO_4 \cdot 5H_2O$, and others. The experimental data obtained are given below. The experiments were performed by the method described above. Magnesium was used in the form of filings.
Activation of the reaction $NaC_2H_3O_2 \cdot 3H_2O + 3Mg$.
$NaC_2H_3O_2 \cdot 3H_2O + 3Mg$.
Weights: salt—2.72 g, magnesium—1.4 g. Onset of the reaction at about $75^\circ$. No flash; gas evolution slow. On heating to $100^\circ$, 72 cu. cm of gas were evolved. On the walls of the bulb there were drops and streaks of water.
Of the 3 particles of water of crystallization in the molecule of the salt, 0.298 mol entered into reaction, or 9.93%.
$NaC_2H_3O_2 \cdot 3H_2O + 3Mg + \tfrac{1}{2}CuCl_2$.
Weights: salt—2.72 g, magnesium—1.4 g, $CuCl_2$—1.3 g. First experiment. The reaction proceeded on grinding in a mortar.
Second experiment. The mixture was prepared by shaking. The reaction began at $30^\circ$ with a push, during which 130 cu. cm of hydrogen were evolved; upon further heating to $100^\circ$, a further 120 cu. cm. The product of the reaction was a strongly swollen, porous mass.
1.035 mol of water of crystallization entered into reaction, or 34.50%.
$CuCl_2$ activates.
$NaC_2H_3O_2 \cdot 3H_2O + 3Mg + ZnCl_2$.
Weights: salt—2.72 g, magnesium—1.4 g, $ZnCl_2$—2.7 g. First experiment: the reaction proceeded energetically on grinding in a mortar.
Second experiment: the reaction proceeded when the powders were mixed in a bulb by shaking—with strong evolution of gas. Immediately incandescence began, at first in one place, then throughout the whole mass. With the gas a white smoke was evolved. A pungent odor. The product of the reaction: a gray, in places whitish mass, porous. On the neck of the bulb much carbon was deposited.
$ZnCl_2$ activates energetically.
$NaC_2H_3O_2 \cdot 3H_2O + 3Mg + HgCl_2$.
Weights: salt—2.72 g, magnesium—1.4 g, $HgCl_2$—5.4 g. First experiment: the reaction proceeded on grinding in a mortar.
Second experiment: the reaction proceeded with a push when the powders were mixed in a bulb by shaking. 120 cu. cm of gas were evolved; upon further heating to $100^\circ$, a further 80 cu. cm. The product of the reaction was a gray, sintered, porous mass.
Entered into reaction, crystallization water: 0.828 mol, or 27.60%.
$\mathrm{HgCl_2}$ activates energetically.
$$ \mathrm{NaC_2H_3O_2 \cdot 3H_2O + 3Mg + AlCl_3.} $$
Weighed portions: salt—2.72 g, magnesium—1.4 g, $\mathrm{AlCl_3}$—2.7 g. The reaction began only when the flask with the powders was shaken. An energetic, but calm, evolution of gas; the apparatus could not accommodate the entire quantity. White vapors were also evolved. The reaction product was a caked, porous mass, covered on top with a white sublimate. On the walls, transparent crystals; the odor of the products of dry distillation was perceptible.
$\mathrm{AlCl_3}$ activates energetically.
$$ \mathrm{NaC_2H_3O_2 \cdot 3H_2O + 3Mg + SbCl_3.} $$
Weighed portions: salt—2.72 g, magnesium—1.4 g, $\mathrm{SbCl_3}$—4.5 g. The reaction began when the flask with the powders was shaken. Hydrogen was evolved slowly, in all 70 cubic cm. The reaction product was a caked, darkish mass and transparent crystals. The odor of the products of dry distillation was perceptible.
Entered into reaction, crystallization water: 0.290 mol, or 9.66%.
$\mathrm{SbCl_3}$ activates energetically.
$$ \mathrm{NaC_2H_3O_2 \cdot 3H_2O + 3Mg + CrCl_3.} $$
Weighed portions: salt—2.72 g, magnesium—1.4 g, $\mathrm{CrCl_3}$—3.2 g. The reaction began when the powders were shaken in the flask—without heating. Hydrogen evolved in all 160 cubic cm.
Entered into reaction, 0.662 mol of crystallization water, or 22.08%.
$\mathrm{CrCl_3}$ activates energetically.
$$ \mathrm{NaC_2H_3O_2 \cdot 3H_2O + 3Mg + I_2.} $$
Weighed portions: salt—2.72 g, magnesium—1.4 g, iodine—2.5 g. The reaction occurred when the mixture of magnesium and salt was poured onto iodine. A slow evolution of gas, in all 90 cubic cm. The reaction product was a darkish caked mass, at the bottom fused and impregnated with iodine.
Entered into reaction, crystallization water: 0.376 mol, or 12.42%.
$\mathrm{I_2}$ activates energetically.
$$ \mathrm{NaC_2H_3O_2 \cdot 3H_2O + 3Mg + FeCl_3.} $$
Weighed portions: salt—2.72 g, magnesium—1.4 g, $\mathrm{FeCl_3}$—3.2 g. The reaction began when the powders were shaken in the flask. The entire contents of the flask became red-hot; white smoke was evolved. In the flask there was a darkish, strongly porous mass; on the walls, carbon.
$\mathrm{FeCl_3}$ activates energetically.
For greater convenience in reviewing them, the experimental data given have been arranged in the form of Table 7, p. 46.
TABLE 7.
| Reaction: $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + activator.}$ |
Temperature at the beginning of the reaction | Amount of water of crystallization that had entered into reaction by $100^\circ$: molecules |
Amount of water of crystallization that had entered into reaction by $100^\circ$: % |
|---|---|---|---|
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg}$ | $75^\circ$ | 0.298 | 9.93 |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + ZnCl_2}$ | on shaking and rubbing | calcination and dry distillation | calcination and dry distillation |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + HgCl_2}$ | on rubbing | 0.828 | 27.60 |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + AlCl_3}$ | on shaking; | the apparatus could not hold the evolved hydrogen. | the apparatus could not hold the evolved hydrogen. |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + SbCl_3}$ | on shaking | $0.290^*)$ | $9.96^*)$ |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + CrCl_3}$ | on shaking | $0.662^*)$ | $22.08^*)$ |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + J_2}$ | on contact | $0.372^*)$ | $12.42^*)$ |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + FeCl_3}$ | on shaking; distillation. | calcination of the mixture and dry | calcination of the mixture and dry |
| $\mathrm{NaC_2H_3O_2\cdot 3H_2O + 3Mg + \tfrac12 CuCl_2}$ | on rubbing | 1.035 | 34.50 |
Activation of the reaction $\mathrm{MgCl_2\cdot 6H_2O + 6Mg}$.
$\mathrm{MgCl_2\cdot 6H_2O + 6Mg}$.
Charges: salt—2.03 g, magnesium—1.4 g. No visible reaction. On heating to $100^\circ$, 20 cubic cm of hydrogen were evolved.
Of the 6 molecules of water of crystallization, the following entered into reaction: 0.166 mol., or 2.76%.
$\mathrm{MgCl_2\cdot 6H_2O + 6Mg + ZnCl_2}$.
Charges: salt—2.03 g, magnesium—1.5 g, $\mathrm{ZnCl_2}$—1.4 g. The separate components of the mixture were poured into the flask one after another. The reaction began at $60^\circ$ without a jolt. Vigorous evolution of gas. 170 cubic cm were collected.
Water of crystallization entered into reaction: 1.407 mol., or 23.46%.
$\mathrm{ZnCl_2}$ activates.
$\mathrm{MgCl_2\cdot 6H_2O + 6Mg + HgCl_2}$.
Charges: salt—2.03 g, magnesium—1.5 g, sublimate—2.7 g. Into the flask there was first poured sublimate, then the mixture of magnesium and salt. The reaction began with a jolt at $55^\circ$. 100 cubic cm of hydrogen were evolved. Upon further heating to $100^\circ$, no more gas was evolved.
Water of crystallization entered into reaction: 0.828 mol., or 13.80%.
$\mathrm{HgCl_2}$ activates.
*) The comparatively small amount of water that entered into reaction is explained by the fact that it is quite impossible to mix the mixture thoroughly.
\[ \mathrm{MgCl_2\cdot 6H_2O + 6Mg + AlCl_3.} \]
Weights: salt—2.03 g, magnesium—1.5 g, \(\mathrm{AlCl_3}\)—1 g. There was no flash on heating to \(100^\circ\). The external appearance of the mixture did not change. 68 cubic cm of hydrogen was evolved.
Of the water of crystallization, there entered into reaction: 0.563 mol., or 9.36%.
\(\mathrm{AlCl_3}\) activates weakly.
\[ \mathrm{MgCl_2\cdot 6H_2O + 6Mg + 2SnCl_2.} \]
Weights: salt—2.03 g, magnesium—1.5 g, \(\mathrm{SnCl_2}\)—3.8 g. Mixed in a mortar. The reaction proceeded with a jolt at \(60^\circ\). The whole mass became red-hot. About 335 cubic cm of gas was evolved at once. External appearance of the reaction product: a white, porous mass penetrated with cavities.
Of the water of crystallization, there entered into reaction: 2.773 mol., or 46.22%.
\(\mathrm{SnCl_2}\) activates vigorously.
\[ \mathrm{MgCl_2\cdot 6H_2O + 6Mg + SbCl_3.} \]
Weights: salt—2.03 g, magnesium—1.5 g, \(\mathrm{SbCl_3}\)—2.2 g. Mixed in a flask. The reaction proceeded with a jolt at \(55^\circ\). External appearance of the reaction product: a black mass. About 80 cubic cm of hydrogen was evolved.
Of the water of crystallization, there entered into reaction: 0.662 mol., or 11.04%.
\(\mathrm{SbCl_3}\) activates.
\[ \mathrm{MgCl_2\cdot 6H_2O + 6Mg + CrCl_3.} \]
Weights: salt—2.03 g, magnesium—1.5 g, \(\mathrm{CrCl_3}\)—1.9 g. There was no flash. Heating was carried out to \(100^\circ\). 44 cubic cm of hydrogen was evolved.
Of the water of crystallization, there entered into reaction: 0.364 mol., or 11.04%.
\(\mathrm{CrCl_3}\) activates weakly.
\[ \mathrm{MgCl_2\cdot 6H_2O + 6Mg + FeCl_3.} \]
Weights: salt—2.03 g, magnesium—1.5 g, \(\mathrm{FeCl_3}\)—1.5 g. The weights were poured entirely into the flask one after another. A very vigorous reaction began at \(50^\circ\). Much gas was evolved; its quantity was not measured, since at the end of the experiment a rubber tube of the apparatus came off.
\(\mathrm{FeCl_3}\) activates vigorously.
\[ \mathrm{MgCl_2\cdot 6H_2O + 6Mg + J_2.} \]
Weights: salt—2.03 g, magnesium—1.5 g, iodine—1.3 g. The weights were poured into the flask, as in the preceding experiment. The reaction began with a jolt at ordinary temperature upon shaking. 80 cubic cm of hydrogen was collected.
Of the water of crystallization, there entered into reaction: 0.652 mol., or 11.04%.
\(\mathrm{J_2}\) activates vigorously.
$$ \mathrm{MgCl_2 \cdot 6H_2O + 6Mg + CuSO_4.} $$
Charges: salt—2.03 g, magnesium—1.5 g, $\mathrm{CuSO_4}$—1.6 g. The reaction did not start. The external appearance of the mixture did not change. 8 cu. cm of hydrogen was evolved.
$\mathrm{CuSO_4}$ does not activate.
The results obtained are brought together in Table 8.
TABLE 8.
| Reaction: $\mathrm{MgCl_2 \cdot 6H_2O + 6Mg}$—activator. |
Temperature at the beginning of the reaction. |
Amount of water of crystallization that had entered into reaction up to $100^\circ$: molecules |
Amount of water of crystallization that had entered into reaction up to $100^\circ$: % |
|---|---|---|---|
| $\mathrm{MgCl_2 \cdot 6H_2O + 6Mg}$ | not observed | 0.165 | 2.76 |
| $\mathrm{MgCl_2 \cdot 6H_2O + 6Mg + ZnCl_2}$ | $60^\circ$ | 1.407 | 23.46 |
| » » $\mathrm{+ HgCl_2}$ | $55^\circ$ | 0.828 | 13.80 |
| » » $\mathrm{+ AlCl_3}$ | not observed | 0.563 | 9.36 |
| » » $\mathrm{+ 2SnCl_2}$ | only at $60^\circ$ and upon ignition of the mixture | 2.773 | 46.22 |
| » » $\mathrm{+ SbCl_3}$ | $55^\circ$ | 0.662 | 11.04 |
| » » $\mathrm{+ CrCl_3}$ | not observed | 0.364 | 6.07 |
| » » $\mathrm{+ I_2}$ | at ordinary temperature | 0.662 | 11.04 |
| » » $\mathrm{+ FeCl_3}$ | $50^\circ$ | abundant evolution of hydrogen | |
| » » $\mathrm{+ CuSO_4}$ | does not activate |
Activation of the reaction $\mathrm{CuSO_4 \cdot 5H_2O + 5Mg}$. With the crystalline hydrate $\mathrm{CuSO_4 \cdot 5H_2O}$, the metal Mg, in the form of powder or dust, does not react when heated to $100^\circ$. In the presence of the substances which in the preceding experiments proved to be activators, the reaction proceeds in the following manner. In all experiments the magnesium was taken in the form of dust.
$$ \mathrm{CuSO_4 \cdot 5H_2O + 5Mg + CuCl_2.} $$
Charges: salt—1.25 g, magnesium—0.60 g, $\mathrm{CuCl_2}$—0.7 g. A strong reaction with a flash at $45^\circ$. Much gas was evolved at once. The gradual evolution of gas continued further when the mixture was heated to $100^\circ$. 172 cu. cm of hydrogen were collected.
Of the 5 molecules of water of crystallization of the crystalline hydrate, 2.848 mol., or 56.96%, entered into reaction.
$\mathrm{CuCl_2}$ activates vigorously.
$$ \mathrm{CuSO_4 \cdot 5H_2O + 5Mg + ZnCl_2.} $$
Charges: salt—2.5 g, magnesium—1.2 g, $\mathrm{ZnCl_2}$—1.4 g. The reaction began at about $70^\circ$; almost immediately thereafter there followed a strong explosion.
$\mathrm{ZnCl_2}$ activates vigorously.
$\mathrm{CuSO_4\cdot 5H_2O + 5Mg + HgCl_2}$.
Weights: salt—2.50 g, magnesium—1.20 g, $\mathrm{HgCl_2}$—2.7 g. The reaction proceeded with a jolt at $70^\circ$. Immediately 140 cu. cm of hydrogen was evolved, then, on heating to $100^\circ$, another 40 cu. cm.
1.490 mol. of water of crystallization, or 29.80%, entered into the reaction.
$\mathrm{HgCl_2}$ activates.
$\mathrm{CuSO_4\cdot 5H_2O + 5Mg + AlCl_3}$.
Weights: salt—2.50 g, magnesium—1.20 g, $\mathrm{AlCl_3}$—1.3 g. The reaction proceeded with a jolt at $60^\circ$. On the surface of the mixture there was a white coating, apparently $\mathrm{MgCl_2}$. On heating to $100^\circ$, 150 cu. cm of gas was collected.
1.242 mol., or 24.84%, of water of crystallization entered into the reaction.
$\mathrm{AlCl_3}$ activates.
$\mathrm{CuSO_4\cdot 5H_2O + 5Mg + SnCl_2}$.
Weights: salt—2.50 g, magnesium—1.20 g, $\mathrm{SnCl_2}$—1.9 g. The reaction proceeded with a jolt at $75^\circ$. 120 cu. cm of hydrogen was evolved. A dark-gray mass; no sublimation products. Drops of water on the neck of the flask.
0.993 mol., or 19.87%, of water of crystallization entered into the reaction.
$\mathrm{SnCl_2}$ activates the reaction.
$\mathrm{CuSO_4\cdot 5H_2O + 5Mg + SbCl_3}$.
Weights: salt—2.50 g, magnesium—1.20 g, $\mathrm{SbCl_3}$—3.0 g. The reaction proceeded with a strong jolt at $60^\circ$. At the same time 72 cu. cm of hydrogen was evolved. On further heating, hydrogen was not evolved. In the flask there was a caked mass of black color, stratified and with cavities.
0.596 mol. of water of crystallization, or 11.92%, entered into the reaction.
$\mathrm{SbCl_3}$ activates.
$\mathrm{CuSO_4\cdot 5H_2O + 5Mg + CrCl_3}$.
Weights: salt—2.50 g, magnesium—1.20 g, $\mathrm{CrCl_3}$—1.6 g. The reaction proceeded with a jolt at $70^\circ$. 150 cu. cm of hydrogen was evolved. On further heating, hydrogen apparently was not evolved.
1.242 mol. of water of crystallization, or 24.84%, entered into the reaction.
$\mathrm{CrCl_3}$ activates.
$\mathrm{CuSO_4\cdot 5H_2O + 5Mg + CuSO_4}$.
Weights: salt—2.50 g, magnesium—1.20 g, $\mathrm{CuSO_4}$—1.6 g. The reaction does not proceed. There are many drops of water on the walls of the flask.
$\mathrm{CuSO_4}$ does not activate.
\[ \mathbf{CuSO_4\cdot 5H_2O + 5Mg + \tfrac{1}{2}I_2.} \]
Weights: salt—2.50 g, magnesium—1.20 g, iodine—1.30 g. The reaction proceeded very vigorously at 50°. Immediately thereafter a strong explosion occurred.
Iodine activates vigorously.
\[ \mathbf{CuSO_4\cdot 5H_2O + 5Mg + FeCl_3.} \]
Weights: salt—2.50 g, magnesium—1.20 g, FeCl\(_3\)—1.6 g. The reaction began with a strong jolt at 60°. The test tube was torn apart, and therefore the amount of gas was not measured. The reaction product was a dark, sharply stratified mass, permeated with bubbles.
FeCl\(_3\) activates vigorously.
The results obtained are brought together in Table 9.
TABLE 9.
| Reaction: \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg +}\) activator |
Temperature of the beginning of the reaction | Amount of water of crystallization that entered into reaction up to 100°: molecules |
Amount of water of crystallization that entered into reaction up to 100°: % |
|---|---|---|---|
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg}\) | at temperature up to 100° | does not react | — |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + CuCl_2}\) | 45°; jolt | 2.848 | 56.96 |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + \tfrac{1}{2}I_2}\) | 50° | explosion | — |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + FeCl_3}\) | 60°; violent; hydrogen could not be collected | — | — |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + AlCl_3}\) | 60°; jolt | 1.242 | 24.84 |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + SbCl_3}\) | 60°; jolt | 0.596 | 11.92 |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + ZnCl_2}\) | 70° | explosion | — |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + HgCl_2}\) | 70°; jolt | 1.490 | 29.80 |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + CrCl_3}\) | 70°; jolt | 1.242 | 24.84 |
| \(\mathrm{CuSO_4\cdot 5H_2O + 5Mg + SnCl_2}\) | 75°; jolt | 0.993 | 19.87 |
Separate activation experiments. In conclusion we shall present a number of separate activation experiments.
\[ \mathbf{Na_2HPO_4\cdot 12H_2O + 12Mg + CuCl_2.} \]
Weights: salt—1.80 g, magnesium—1.50 g, CuCl\(_2\)—2.00 g. The reaction proceeded extremely vigorously when the mixture was triturated in a mortar.
\[ \mathbf{BaCl_2\cdot 2H_2O + 2Mg + \tfrac{1}{4}CuCl_2.} \]
Weights: salt—2.50 g, magnesium—0.50 g, CuCl\(_2\)—0.3 g. The reaction began with a jolt at about 70°. About 40 cu. cm of hydrogen was evolved.
The amount of water of crystallization that entered into reaction was: 0.331 mol., or 16.56%.
\[ \mathbf{BaCl_2\cdot 2H_2O + 2Mg + ZnCl_2.} \]
Weights: salt—4.8 g, magnesium—1.00 g, ZnCl\(_2\)—2.80 g. 116 cu. cm of hydrogen was evolved.
The amount of water of crystallization that entered into reaction was: 0.480 mol., or 24.01%.
\[ \mathrm{Ba(OH)_2\cdot 8H_2O + 9Mg + CuCl_2.} \]
Charges: crystal hydrate—3.10 g; magnesium—2.20 g; \(\mathrm{CuCl_2}\)—1.30 g. The reaction proceeded at ordinary temperature upon grinding the mixture.
Second experiment. The charges were the same. The mixture was prepared by shaking the powders. The reaction proceeded at ordinary temperature very vigorously. The apparatus did not contain all the gas, as a result of which the amount of hydrogen measured is less than the actual amount. 375 cubic cm of hydrogen were collected. The reaction product was a porous mass, white at the bottom, shiny; brownish above, probably from separated copper.
3.105 mol. of water of crystallization entered into the reaction, or 38.81%.
\[ \mathrm{C_2O_4H_2\cdot 2H_2O + 3Mg + CuCl_2.} \]
Charges: acid—1.3 g; magnesium—0.70 g; \(\mathrm{CuCl_2}\)—1.3 g. The reaction began at \(50^\circ\) with a strong jolt. White vapors were evolved. A sharp odor was perceptible from the flask. The reaction product was a mass of layered composition. Upon heating to \(100^\circ\), 140 cubic cm of hydrogen were evolved.
1.159 mol. of water of crystallization entered into the reaction, or 57.95%.
\[ \mathrm{C_3H_4(OH)(CO_2H)_3\cdot H_2O + 3Mg + CuCl_2.} \]
Charges: acid—2.10 g; magnesium—0.70 g; \(\mathrm{CuCl_2}\)—1.3 g. The reaction began with a flash at about \(36^\circ\). The reaction product was a caked, layered mass. Upon heating to \(100^\circ\), in all about 110 cubic cm of hydrogen were evolved, the greater part at the flash.
0.911 mol. of water of crystallization entered into the reaction, or 91.07%.
These experiments are summarized in Table 10.
TABLE 10.
| Reaction: | Temperature of beginning of reaction. | Amount of water of crystallization entering into reaction up to \(100^\circ\): molecules | Amount of water of crystallization entering into reaction up to \(100^\circ\): % |
|---|---|---|---|
| \(\mathrm{Na_2HPO_4\cdot 12H_2O + 12Mg}\) | not observed upon grinding in a mortar | 2.32 | 19.32 |
| \(\mathrm{Na_2HPO_4\cdot 12H_2O + 12Mg + CuCl_2}\) | reaction does not proceed | — | — |
| \(\mathrm{BaCl_2\cdot 2H_2O + 2Mg}\) | \(70^\circ\), jolt | 0.331 | 16.56 |
| \(\mathrm{BaCl_2\cdot 2H_2O + 2Mg + \tfrac14 CuCl_2}\) | \(70^\circ\), jolt | 0.480 | 24.01 |
| \(\mathrm{BaCl_2\cdot 2H_2O + 2Mg + ZnCl_2}\) | \(70^\circ\), jolt | — | — |
| \(\mathrm{Ba(OH)_2\cdot 8H_2O + 5Mg}\) | upon heating to \(190^\circ\) | 0.604 | 7.55 |
| \(\mathrm{Ba(OH)_2\cdot 8H_2O + 9Mg + CuCl_2}\) | at ordinary temperature | 3.105 | 38.81 |
| \(\mathrm{C_2O_4H_2\cdot 2H_2O + 4Mg}\) | not observed | 0.265 | 13.24 |
| \(\mathrm{C_2O_4H_2\cdot 2H_2O + 4Mg + CuCl_2}\) | \(50^\circ\), jolt | 1.159 | 57.95 |
| \(\mathrm{C_3H_4(OH)(CO_2H)_3\cdot H_2O + 3Mg}\) | not observed | 0.339 | 33.94 |
| \(\mathrm{C_3H_4(OH)(CO_2H)_3\cdot H_2O + 3Mg + CuCl_2}\) | \(36^\circ\), flash | 0.910 | 91.07 |
From the experimental material just presented, collected to test the action of activators, it becomes clear that the salts ZnCl₂, HgCl₂, AlCl₃, SnCl₂, SbCl₃, CrCl₃, FeCl₃, CuCl₂, and also I₂, which play the role of activators for the reaction MgSO₄·7H₂O + 7Mg, are also activators for the reactions NaC₂H₃O₂·3H₂O + 3Mg, MgCl₂·6H₂O + 6Mg, CuSO₄·5H₂O + 5Mg, Na₂HPO₄·12H₂O + 12Mg, BaCl₂·2H₂O + 2Mg, Ba(OH)₂·8H₂O + 9Mg, C₂H₄O₂·2H₂O + 4Mg, C₃H₄(OH)(CO₂H)₃·H₂O + 3Mg. The conclusion would seem to suggest itself that the substances listed in Table 5, which are activators for the reactions MgSO₄·7H₂O + 7Mg, will activate the reaction with magnesium of any other crystalline hydrate, or, more generally, that the activating capacity of an activator does not depend on the nature of the crystalline hydrate.
To insist on such a conclusion, however, would be premature: on the one hand, there is still no overwhelming body of experimental material available; on the other hand, the theory of the activating action of activators has only just begun to be developed.
Activation of the reactions of magnesium with anhydrous bases and acids. The experiments described above on the action of magnesium on anhydrous bases and acids showed that anhydrous bases do not react with magnesium with evolution of hydrogen, even when heated to 200°. It was important to ascertain whether this reaction would proceed in the presence of activators.
In all the experiments the activator used was the salt CuCl₂. For one molecule of acid or base, one molecule of activator was taken. The magnesium was taken in the form of dust. Experiments were carried out with the bases Ba(OH)₂, Ca(OH)₂, and with the acids H₃PO₄, HBO₃, HSbO₃. In all cases no perceptible reaction was detected. Experiments with other activators were not performed.
Products of the reaction of magnesium on crystalline hydrates. An attempt to investigate the products of the reaction of magnesium on crystalline hydrates immediately encountered difficulties. The problem of analyzing mixtures for their content of chemical individuals is in general not a simple one, and in the present case preliminary experiments and separate tests showed that a method of analysis would have to be developed. Since this would greatly delay the development of the results already obtained, the systematic investigation of the products of the reaction of magnesium on crystalline hydrates was postponed.
It is, however, highly probable—and individual tests always confirmed this—that the products of the reaction of magnesium on crystalline hydrates of salts in the absence of activators are, in general, the same as in the action of magnesium on aqueous solutions of these same salts, and that a systematic investigation of the reaction products in these cases would hardly yield new results.
The matter stands quite differently in the case of a reaction in the presence of activators. Clarification of the question of what part the activator takes in the reaction is very important, and a systematic study of the reaction products in this case may yield interesting results. It is intended, insofar as possible, to carry out this work in the near future.
Conclusions
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Metallic magnesium reacts with the water of crystallization of crystal hydrates with the evolution of hydrogen.
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The nature of the salt of the crystal hydrate has a definite effect on the intensity of the reaction.
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The addition to the mixture of crystal hydrate and magnesium of certain salts (activators) greatly increases the intensity of the reaction.
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Salts that activate the reaction of magnesium with one crystal hydrate will, apparently, also activate the reaction with magnesium and any other crystal hydrate.
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Anhydrous bases and acids, in the presence and absence of activators, do not react with magnesium with the evolution of hydrogen.
Tomsk, March 25, 1911.*
*) The work was carried out during the period 1905–1906. Its contents were reported at the First Mendeleev Congress in 1907 (Proceedings of the Congress, p. 317). The work appears here in full for the first time.