\[ j = 0.737 - 0.172c - 0.105w - 0.008h + 0.054cw + 0.004ch + \]
\[ + 0.0016wh - 0.0014cwh . \]

Following the mathematical description of the process problem, the next step is to find the values of the parameters corresponding to the maximum resolving power. For this purpose we used the scanning method. From calculations carried out by the scanning method it follows that the maximum value of the function \(y\) (\(j\)) lies on the boundary of the region and corresponds to the following parameter values: \(c = 0.05\) M/l; \(W = 0.25\) V/min; \(h = 5\) μm. Thus, the optimal parameter values correspond to the quantity \(j = 1.83\), which is the maximum value of the resolving power as a function of the parameters \(c, w, h\) within the ranges of variation specified in the work.

References

1. A. G. Stromberg, A. A. Zheltonozhko, A. A. Kaplin. ZhAKh, 28, 1045, 1973.
2. V. A. Igolinskii. Izvestiya TPI, 148, 14, 1967.

STUDY ON THE ANALYSIS OF WATER-SOLUBLE SALTS AND CRYSTALS OF COMPLEX COMPOSITION BY THE AMALGAM-POLAROGRAPHIC METHOD

N. V. Podkorytova, A. A. Kaplin, N. T. Rud, V. I. Kuleshov

In this work, the amalgam-polarographic method is applied to the analysis of water-soluble salts and ferroelectric crystals of complex composition \((\mathrm{CsH_2AsO_4}, \mathrm{KH_2PO_4}, \mathrm{LiIO_3})\). In contrast to the chemical-spectral analytical procedure for rubidium and cesium arsenates /1/, the solutions of the salts being analyzed can in most cases be used as polarographic supporting electrolytes for the determination of impurities, which eliminates the stage of sample decomposition. For the determination of \(\mathrm{Cd}, \mathrm{Cu}, \mathrm{Bi}, \mathrm{Pb}\), a mercury film electrode on a silver substrate and a cell with insert cups were used. Nickel was determined by anodic-cathodic polarography with accumulation (ACPN) /2/ in a circulating electrolyzer /3/; the reference electrode was a saturated calomel electrode. The impurity content in the reagents and solutions used was monitored by the APN and ACPN methods.

The polarographic behavior of \(10^{-6}\)–\(10^{-9}\) g/ml \(\mathrm{Cd}, \mathrm{Pb}, \mathrm{Cu}, \mathrm{Bi}, \mathrm{Ni}\) in \((0.05 \div 0.1)\) M solutions of \(\mathrm{CsH_2AsO_4}\) and \(\mathrm{KH_2PO_4}\), stud-

used as supporting electrolytes. In the determination of bismuth, the supporting-electrolyte solutions were acidified with hydrochloric acid to a final concentration in the supporting electrolyte of 0.25 M. It was established that the joint electrolysis of \(Cd\), \(Cu\), \(Pb\) from solutions of \(KH_2PO_4\) and \(CsH_2AsO_4\) should be carried out at a potential \((\varphi)\) of \(-1.7\) V, and \(Bi\) at \(\varphi = (-0.2)\) V. The dependences of the anodic-current values on concentration from \(10^{-9}\) to \(10^{-6}\) g/ml are linear. Studies on the determination of \(Ni\) by the AKPN method were described earlier /3/. The interfering effect of \(As^{V}\) on \(Ni\) in solutions of salts and crystals of \(CsH_2AsO_4\) was eliminated by distilling off \(As\)(III) as the bromide. Solutions of \(LiIO_3\) cannot be used as a supporting electrolyte for the determination of impurities, since the salt anion is polarographically active; therefore samples of \(LiIO_3\) were subjected to acid decomposition with hydrochloric acid. On the basis of the investigations carried out, methods were developed for determining \(Cd\), \(Pb\), \(Cu\), \(Bi\), \(Ni\) in salts and crystals of \(LiIO_3\), \(CsH_2AsO_4\), \(KH_2PO_4\).

Determination of \(Cd\), \(Pb\), \(Cu\), \(Bi\) in salts and crystals of \(KH_2PO_4\), \(LiIO_3\), \(CsH_2AsO_4\). A 0.1–0.2 g sample is dissolved in a clean quartz beaker in 5 ml of water. In the analysis of \(LiIO_3\), the sample is first decomposed by adding 1 ml of concentrated HCl three times and each time evaporating the residue to moist salts. The solution is placed in the cell and, after removal of oxygen by a stream of inert gas for 5–10 min, at \(\varphi = -1.7\) V, the anodic peaks of \(Cd\), \(Pb\), \(Cu\) are recorded; the peak potentials are \((-0.6)\), \((-0.4)\), and \((+0.05)\) V, respectively. To determine \(Bi\), 2 drops of a (7–8) M HCl solution are added to the solution, electrolysis is carried out for 3–10 min at \(\varphi = -0.2\) V, and the anodic peaks of \(Bi\) are recorded; the peak potential is \(-0.07\) V.

Determination of nickel in salts and crystals of \(KH_2PO_4\), \(CsH_2AsO_4\), \(LiIO_3\). Nickel is determined in the solution after the determination of \(Cd\), \(Pb\), \(Cu\), \(Bi\), \(Zn\), since these metals do not interfere with its determination /3/. The solution is evaporated to moist salts; the residue is dissolved in 5 ml of 0.1 M \(KCNS\) solution, and \(Ni\) is concentrated at \(\varphi = -1.7\) V, accumulation time 1–2 min from the circulating solution; oxidation of \(Cd\), \(Pb\), \(Cu\), etc. from the amalgam is carried out for 1 min at \(\varphi = (-0.3)\) V. After the circulation pump is switched off, the electrode is lowered into the capillary and dissolution is carried out at \(\varphi = +0.05\) V for 1 min. Recording of the cathodic polarogram is begun at \(\varphi = -0.25\) V after holding the electrode at this potential for 1 min; the poten-

dial of the cathodic peak of $Ni$ ($-0.6$) V. The sensitivity of the proposed methods is $(3 \div 8)\cdot 10^{-7}\%$; the coefficient of variation is $8 \div 10\%$ ($n=5$); the analysis time for one sample is 1.5–2.5 hours.

When determining $Ni$ in salts and crystals of $CH_2AgO_4$, 2 ml of conc. $HBr$ is added to the residue 3 times, and the solution is evaporated to moist salts; the residue is dissolved in 0.5 ml of conc. $HNO_3$ and again evaporated to moist salts.

Literature

1. Yu. A. Fedyashina, I. G. Yudelevich, T. G. Sorokina. Zh. analit. khimii, 21, 10, 1232–1235, 1966.
2. V. I. Kuleshov. “Zavodskaya laboratoriya,” 34, 950 (1967).
3. V. I. Kuleshov, N. V. Podkorytova, S. I. Nazarova. “Zavodskaya laboratoriya,” 39, No. 3, 284–285, 1974.

ON CERTAIN FEATURES OF INTERACTIONS IN SYSTEMS WITH ELECTRON-TYPE COMPOUNDS WHEN STUDIED BY STRIPPING POLAROGRAPHY

A. A. Kaplin, I. P. Mamontova

The study of the mutual influence of elements in mercury and on solid electrodes is one of the principal physicochemical problems of stripping polarography. A comparatively large number of works on the study of the mutual influence of elements in mercury is known; the formation of intermetallic compounds (i.m.c.) has been noted, and the composition and solubility products of a number of i.m.c. in the solid and liquid phases have been determined. However, the theoretical and experimental studies developed earlier on the mutual influence of elements in the method of amalgam and film stripping polarography, based on approximations of ideal solutions, did not make it possible to take into account interaction parameters or to correlate stripping-polarography data with thermodynamic quantities. The thermodynamic approach developed in works [1, 2], taking into account changes in the activity of the components in the system, offers both the fundamental possibility of calculating certain thermodynamic parameters for metals and alloys and the use, in theoretical and experimental studies in the method of stripping polarography, of thermodynamic data obtained by other independent methods in order to predict the character of current–voltage curves in the presence of an interaction effect in the system.