SU1679368A1 - Method of determination of cobalt (ii) in solutions of drying agents in styrene - Google Patents

Abstract

The invention relates to methods for determining cobalt (II) in styrene solutions of desiccants, and can be used to control the content of metals in them and improves accuracy, acceleration, and ability to analyze styrene solutions of lead (II), manganese (II) and zinc siccatives (Ii) with a single solvent for potentiometric indication of the end point of the titration, as well as to simplify the process for visual indication of the end point of the titration. The essence of the invention is to add to a 0.5-4 g sample of a solution of siccatives in styrene, 40-60 ml of water to a ratio of the aqueous and organic phases in the resulting suspension (10-100): 1 and subsequent titration of 0.1-0.2 n , hydrochloric acid solution and indicator bromophenol blue. 1 h. the item f., 1 tab.

Description

The invention relates to physicochemical methods for the analysis of solutions of naphthenic acid and fatty acid salts of cobalt (II) and other metals (siccatives), most often used for curing paint coatings, and can be used to control the content of metals in them.

The aim of the invention is to improve the accuracy, acceleration, enable the analysis of styrene solutions of lead (Ic), manganese (II) and zinc (I) siccatives with a single solvent in the potentiometric indication of the end point of the titration, as well as simplify the analysis when visually displaying titration

The goal is achieved by mixing a desiccant in white alcohol (styrene) with water to obtain a suspension and titrating with an acid solution in water. Equivalence points are defined by:

with potentiometric titration with glass and calomel electrodes

on a pH meter based on potentiometric titration curves for potential jumps;

visual titration of lead, manganese, and zinc siccatives by changing the color of the bromophenol blue indication (2-3 drops of a 0.1-0.2% aqueous solution in water) from blue to yellow;

by visual titration of the cobalt desiccant until the pink color of the emulsion disappears.

PRI me R 1. Definition of cobalt (II) in the desiccant (NC-2). For the determination of cobalt (II) a commercial desiccant NK-2, corresponding to TU 6-05-1075-76, is used. Cobalt is determined by a potentiometric method in the acetone-toluene system (4: 1) and the proposed method.

3-4 g of desiccant NK-2, weighted with an accuracy of 0.0002 g, are placed in a 150 ml beaker. mix thoroughly until a suspension is obtained, titrate with 0.2 N, hydrochloric acid at constant (L

WITH

oh h

s about

stir vigorously and measure the pH of the suspension. The disappearance of the pink color of the suspension corresponds to the equivalence point on the potentiometric titration curve. The bromophenol blue indicator is used to enhance the contrast of the color transition, i.e. the accuracy of the analysis. The color transition interval of the indicator corresponds to a potential jump on the potentiometric titration curve. The content of cobalt (Xi) in the desiccant is calculated by the formula

Y1 0.005894.

gtz

where 0.005894 is the amount of cobalt (g), corresponding to 1 ml of 0.2 n hydrochloric acid solution;

YI - volume of 2 n, hydrochloric acid, spent on titration, ml;

mi - desiccant suspension,

PRI mme R 2. Definition of lead (II) in the desiccant NF-1. For the analysis, a commercial desiccant NF-1 is used that meets the requirements of GOST 1003-73. Lead is determined by a potentiometric method in methyl ethyl ketone and the proposed method.

A weighed sample of 0.5-1 g, weighted with an accuracy of 0.002 g, is placed in a 150 ml beaker, 50 ml of distilled water is added, 2 drops of a 0.1% solution of bromophenol blue in water are mixed thoroughly to obtain a suspension. titrated with 0.2 n. with a solution of hydrochloric acid in water with constant vigorous stirring and the pH of the suspension is measured.

The content of lead (II) (X2) is calculated by the formula

Y2-0,02072

X2

GP2

100,

where Y2 is the volume of 0.2 n. hydrochloric acid spent on titration, ml;

Ш2 - siccative hitch, g;

0,02072 - the amount of lead (g), corresponding to 1 ml of 0.2 n. hydrochloric acid solution.

PRI me R 3. Determination of zinc (II) in the siccative NF-7, For analysis, use the commercial sikkativ NF-7, which meets the requirements of GOST 1003-73. Zinc is determined by a potentiometric method in methyl ethyl ketone and the proposed method.

A portion of the desiccant 0.5-2 g, weighted with an accuracy of 0.0002 g, titrated as described in example 1. The zinc content (Xs) is calculated by the formula

Y3-0.006537. hh

where 0,006537, - the amount of zinc (g), corresponding to 1 ml of 0.2 n. hydrochloric acid solution;

TZ - weight of the sample 2.

s - volume 0.2 n. hydrochloric acid spent on titration, ml.

PRI me R 4. Definition of manganese (P) in the desiccant LCD-3. For the determination of manganese, a commercial desiccant LC-3, corresponding to Specification 6-10-1641-77, is used. The determination of zinc is carried out by a potentiometric method in a mixture of methyl ethyl ketone - toluene (4: 1) and the proposed method.

A weighted desiccant 2-3, g weighted

with an accuracy of 0.0002 g, titrated as described in example 1.

The content of manganese (X4) is determined by the formula

-04-0.005494

X4w10 ° where 0.005494 is a manganese glaciness (g), corresponding to 1 ml 0.2 n. hydrochloric acid solution; gp4 - the weight of the sample,

m - volume 0.2 n. hydrochloric KIJC-lots spent on titration, ml.

The results of the determination of manganese (II) in the desiccant LC-3, as well as the results of the determination of cobalt (II) and other metals in the desiccants are listed in the table.

Thus, the proposed method allows the determination of various metals in driers, the elimination of organic solvents for titration, the increase in the rate

accuracy and greatly simplify the analysis. The method allows both visual and instrumental registration of the equivalence point.

Claims (2)

1. A method for determining cobalt (II) in styrene solutions of desiccants, including diluting the sample with a solvent and subsequent titration with a solution of hydrochloric acid, the fact that, in order to increase accuracy, accelerate the ability to analyze styrene solutions of lead (II), manganese (I) and zinc (II) solvent with one solvent in a potentiometric indication of the end point of the titration, as well as simplify the process in visual indication of the final titration points; water is used as a solvent and titration is carried out with an aqueous solution of hydrochloric acid. 2. A method according to claim 1, characterized in that, in order to simplify the process, a visual method of indicating the end point of the titration in the presence of a bromophenol blue indicator is carried out.