PHOTOMETRIC DETERMINATION OF SMALL AMOUNTS OF TITANIUM IN PERCHLORIC ACID, AMMONIUM AND SODIUM PERCHLORATES, AND PHOSPHOR L-34 USING DIANTIPYRYLMETHANE

L. L. Skripova, G. A. Chervenchuk, A. N. Pokrovskaya

(Recommended by the scientific-methodological seminar of the Faculty of Chemical Technology)

Diantipyrylmethane, as a highly selective and sensitive reagent, is widely used for the photometric determination of titanium in various objects. In an acidic medium, diantipyrylmethane forms with titanium a yellow-colored complex cation \([TiD_3]^{4+}\) [1, 3]. In terms of its sensitivity \((0.01\ \mu\text{g}/\text{ml})\), this method is 25 times superior to the method with hydrogen peroxide and is comparable with the method in which chromotropic acid is used.

Unlike the latter, the use of diantipyrylmethane does not require strict regulation of pH. The complex is formed over a wide acidity range from 0.1 to 5–6 N hydrochloric acid. Vanadium, niobium, tantalum, tungsten, molybdenum, iron (2+), cobalt, nickel, chromium, aluminum, manganese, and others do not interfere with the determination [4].

A very important advantage, possessed by none of the known colorimetric methods for determining titanium, is the possibility of determining the latter in the presence of significant amounts of fluorides and phosphates [5], which is essential in the determination of titanium in phosphor L-34, which contains fluorides and phosphates in its composition.

Iron (3+) interferes with the reaction, but it can be reduced with ascorbic acid. The anion of perchloric acid also interferes; with diantipyrylmethane it gives a precipitate insoluble in water but readily soluble in chloroform.

We have established that the interaction of the \(ClO_4^1\) ion with diantipyrylmethane occurs in a ratio of 1:2. The precipitate is difficult to separate from the solution. To avoid the interfering effect of the \(ClO_4^1\) ion, we used a method for separating titanium from solutions containing the \(ClO_4^1\) ion in the form of hydroxide with a collector, for which iron hydroxide was chosen [6].

Diantipyrylmethane was synthesized by us according to the procedure given in the works of V. P. Zhivopistsev [7].

Course of analysis. A weighed portion of the substance, 1–2 g, placed in a 50 ml beaker, is dissolved in 5–6 ml of water; a solution of ferric chloride is added in an amount corresponding to 0.006–0.007 g of iron; the mixture is heated almost to boiling, and iron and titanium are precipitated with concentrated ammonia, adding it until a faint odor appears. The mixture is diluted with hot water to 10–15 ml and filtered through a small filter with a white or red ribbon. The beaker is washed with hot water 3 times, and the precipitate on the fil—

... three times. The precipitate on the filter is dissolved with a 25% sulfuric acid solution, adding it dropwise. The solution is collected in the same beakers in which the precipitation was carried out. The filters are washed several times with 20% sulfuric acid solution. To the resulting solution are added 0.07–0.08 g of ascorbic acid, 2 drops of a 5% solution of copper sulfate (a catalyst for the reduction of iron (3+)), and 5 ml of a 5% solution of diantipyrylmethane. The solution is transferred to 25 ml volumetric flasks, the volume is brought to the mark with 25% sulfuric acid solution, mixed thoroughly, and after 30–40 minutes colorimetry is carried out on an FEK-N-57 in 50 mm cuvettes with light filter No. 2 (413 mμ). The comparison solution is water. A blank experiment is also performed. The amount of titanium is determined from a calibration curve constructed under the same conditions as those under which the sample is treated.

When determining titanium in phosphor L-34, a 0.25 g sample of the latter is treated in a 50 ml beaker, with heating for 5–7 min, with 5 ml of concentrated purified hydrochloric acid. The insoluble residue is filtered off through a small ashless white-ribbon filter, and the filter is washed several times with hot water. The solution is collected in a 25 ml volumetric flask. The residue with the filter is ashed in a platinum crucible and fused with 0.12 g of potassium hydrosulfate with the addition of 2–3 drops of concentrated sulfuric acid. The melt is dissolved in water with the addition of 1–2 drops of concentrated hydrochloric acid, and the resulting solution is combined with the main solution from the sample. Further treatment of the solution is carried out as described above, but without addition of iron and precipitation with hydroperoxide. A blank experiment is obligatory. All reagents and potassium hydrosulfate are introduced into the latter.

The method was checked by the method of additions. The experimental data were processed by the method of mathematical statistics, and the results are summarized in the table.

Table

REFERENCES

1. A. A. Minin. Complex compounds of titanium with certain antipyrine derivatives. Scientific Notes of Perm University, XV, 4, 96, 1958.

2. A. A. Minin, S. A. Erofeeva. On the colorimetric determination of titanium using diantipyrylmethane. Scientific Notes of Perm University, XIX, 1, 97, 1961.

3. A. K. Babko, M. M. Tananaiko. Study of complex formation in the system titanium (4+)—diantipyrylmethane—rhodanide. Journal of Inorganic Chemistry, 7, 562, 1962.

4. V. P. Zhivopistsev. Application of diantipyrylmethane in analytical chemistry. Factory Laboratory, 9, 1043, 1965.

5. V. P. Zhivopistsev, A. A. Minin, L. L. Milyutina. Diantipyrylmethane as a reagent for the determination of titanium. Abstracts of reports at the VII Conference of Workers of Factory and Production Laboratories of Kazakhstan and Central Asia. 1964.

6. V. A. Zinchenko, S. I. Rudina. Colorimetric determination of titanium in aluminum and magnesium using diantipyrylmethane. Factory Laboratory, 8, 956, 1961.

7. V. P. Zhivopistsev. A new method for the determination of cadmium. Factory Laboratory, 10, 1186, 1950.