Determination of ?-naphthol in water by the APN method
Abstract Generated abstract
A method is described for the indirect determination of beta-naphthol in water using amalgam polarography with accumulation. The approach is based on the observed suppression of the anodic cadmium dissolution peak after beta-naphthol is introduced, with measurements made by comparing cadmium peak heights at electrolysis potentials of -0.7 or -0.8 V relative to -1.4 V. The procedure specifies reagents, electrode equipment, accumulation conditions, and use of calibration curves to estimate beta-naphthol concentration. Verification on synthetic samples at several concentration levels gave relative errors of about 3.9 to 9.9 percent, indicating applicability of the method for water analysis under the tested conditions.
Full Text
DETERMINATION OF β-NAPHTHOL IN WATER BY THE APN METHOD
T. V. Gomza, V. E. Gorodovykh
(Presented by the scientific seminar of the Department of Technology of Inorganic Substances and Electrochemical Production)
In studying the effect of adsorption of β-naphthol on electrochemical processes involving cadmium under the conditions of the method of amalgam polarography with accumulation, it was found that introduction of β-naphthol into the solution causes suppression of the anodic cadmium peak, depending on the electrolysis potential (Fig. 1). This effect was used as the basis for a method of indirect determination of β-naphthol in waters.
Fig. 1. Decrease in the peak-current density of anodic dissolution of cadmium with increasing β-naphthol concentration. The electrolysis potentials are indicated on the curves.
Required reagents and solutions
- Water, triply distilled with the addition of potassium permanganate.
- Cadmium sulfate, especially pure, calcined, \(10^{-3}\) M solution.
- Sulfuric acid, especially pure, 0.25 N solution.
- Water under investigation.
Apparatus used
- OH-101 polarograph.
- Electrochemical cell with insert cups [1].
- Film electrode on a silver support [2] or on a support made of silver-plated platinum [3].
Procedure
Into a polarographic cup of 12 ml capacity are introduced 5 ml of the water to be analyzed, 1 ml of \(10^{-3}\) M cadmium sulfate solution, and 4 ml of 0.25 N sulfuric acid solution.
The anodic cadmium peak is recorded at an electrolysis potential of \(-1.4\) V (s.c.e.) without stirring the solution during accumulation; the time
electrolysis for 1–5 minutes. Then the cadmium anodic peak is recorded under the same conditions, but at an electrolysis potential of −0.7 V or −0.8 V.
Fig. 2. Calibration graph for determining the content of β-naphthol in water
The ratio of the peak heights is calculated:
\[ \frac{i_{0.7}}{i_{1.4}} \left( \text{or } \frac{i_{0.8}}{i_{1.4}} \right). \]
The concentration of β-naphthol in the solution is determined from the calibration graph (Fig. 2), where curve 1 corresponds to an electrolysis potential of −0.8 V, and curve 2 to an electrolysis potential of −0.7 V.
An experimental verification of the procedure was carried out on synthetic samples. The verification results are presented in the table.
Table
| Introduced, mg/L | $\varphi_{\mathrm{e}}$, V | Number of parallel measurements | Arithmetic mean, mg/L | Error of the arithmetic mean, mg/L | Relative error, % | Result, mg/L |
|---|---|---|---|---|---|---|
| 8 | −0.7 | 10 | 8.45 | 0.5 | 7.1 | 8.5±0.6 |
| 8 | −0.8 | 10 | 8.97 | 0.35 | 3.90 | 8.97±0.35 |
| 25.4 | −0.7 | 10 | 26.6 | 2.35 | 8.8 | 26.6±2.3 |
| 25.4 | −0.8 | 10 | 26.1 | 1.2 | 4.6 | 26.1±1.2 |
| 127 | −0.8 | 10 | 119 | 11.7 | 9.9 | 119±11.7 |
REFERENCES
- V. I. Kuleshov. Methods for the Analysis of Chemical Reagents and Preparations, IREA, issue 5–6, 1963, p. 22.
- V. A. Igolinsky, A. G. Stromberg. Zavodskaya laboratoriya, 30, 656, 1964.
- L. V. Mishenko, V. A. Trukhacheva, R. Yu. Bek. TsNIIolovo, 1967, No. 1.