CS240786B1 - Method for detection and determination of active chlorine - Google Patents

Abstract

The solution is to react the analyzed sample containing active chlorine with cresol sulfophthalein in solution or on a carrier such as paper and determine the presence and concentration of active chlorine in the sample, depending on the color change. The indicator system allows for quick and easy detection of the active chlorine content. This method of analysis can be used to detect and determine chlorine in bleaching baths, cellulose and paper processing, and the textile industry.

Description

The invention relates to a method for detecting and determining active chlorine.

So far, colorimetry has been used to detect active chlorine, where chlorine has reacted with the reagent 4-dimethylazobenzene-2-carboxylic acid, ie methyl red. The color change was also caused by hydrogen chloride. The minimum detectable amount was 100 chlorine, vn Staszewski, R, - Grzybowski, W. Strzelocki, H., Pat. PLR, No. 112 060.

Chlorine gas also reacts with toluidine to give a blue color. The reaction principle is based on the Orager ' s tubes, Leichnitz, K., Pruhrohrchen Taschenbuch,

5th edition. Dragenwerke G. Lubeck 1982. In addition to color reactions, precipitation reactions are also used for the detection and determination of chlorine. brown spots. For the determination of chlorine in the atmosphere, an instrument based on voltammetric indication with platinum electrodes has been developed. Valeo, D, P .: Pat. Great Britain No. 1,423,314.

The basic methods for determination of active chlorine include iodometric titration. This method of analysis is laborious, time-consuming and labor-intensive. Other procedures are suitable for detection and determination of free and bound chlorine in various oxidation stages. This allows application especially for air control. For the analysis of solutions, with the exception of iodometry, these methods are less suitable, particularly in terms of selectivity. Chlorine detection by 4-dimethylazobenzene-2-carboxylic acid is impaired by the presence of mineral acids and bases. To determine active

240 786 chlorine, i.e., chlorine, which is liberated after acidification and is capable of further oxidation, is not always suitable for the methods of analysis.

The principle of the method for detecting and determining active chlorine is based on reacting the analyzed sample containing active chlorine with cresolsulfophthalein in solution or on a carrier, for example paper, and determining the presence and concentration of active chlorine in the sample by color change.

The main advantages of the method for the detection and determination of active chlorine according to the invention are that it is possible to easily control, in particular, hypochlorite solutions of up to 3% active chlorine content. Compared to the iodometric titration still active chlorine content control, the method of analysis is *

of the present invention is faster and allows implementation by an untrained person.

Example 1

Acetone-water solution was prepared 3,3-dibromkresolsulfoftaleinu concentration 5 mg.ml ^"1, a stock aqueous solution of calcium hypochlorite -2 -1 at a concentration of 1.10 mol.1 hydrogenftalanov.é and buffers at a concentration of 1.10" ¹ mol.l ^"1 of pH 1 to Spd / eSlots K,

Chemickoanalytické tabulky, SNTL Praha 1976. 2 ml of pH 1.0 buffer was added to a tempered cuvette with an edge length of 10 mm at 20 ° C; 3.0 and 5.0, 0.2 ml of reagent solution and 2 ml of calcium hypochlorite solution, prepared by diluting the stock solution to form a set of twenty solutions at concentrations of - 2 - 4 -1

1.10 to 1.10 mol.1 after one tenth of the mole. The change in color depending on the concentration used was graphically evaluated by the change in time at which the original solution decolorized. Measurements were performed on a two-powder recording spectrophotometer at a constant wavelength of 390 µm.

3

Example 2

240 786

An aqueous solution of o-cresolsulfophthalein at a concentration of mg.ml was prepared, a stock aqueous solution of calcium hypochlorite at a concentration of 2 to 1 cc. ,

Gradually 2 ml of buffer solution pH 3.0 was pipetted;

4.0; 5.0, 0.2 ml of reagent and 2 ml of calcium hypochlorite solution, prepared by diluting the stock solution at a concentration of 1 · 10 -5 to 5,10 mol / l in one tenth of a mole. The change in color as a function of the selected concentration was graphically evaluated according to the change in time for the original solution to discolour. Measurements were performed on a double-beam recording spectrophotometer at a constant temperature of 20 ° C and a quartz cuvette with an edge length of 10 mm.

Example 3

10 were prepared in solutions of calcium hypochlorite having a concentration of 1 • 'λ ¹ from 1.10- to 1.10 mol.l after 0.2 moles. Pipettes of 2 ml of 0.1 mol ^/ l acetate buffer pH 3.0 were pipetted into the tubes; 4.0; 5,0ydleSýkory V .: Chemical-Analysis Tables, SNTL Prague 1976, 0.2 ml of 3,3-dibromocresolsulfophthalein solution was added. After the addition of 2 ml of the hypochlorite solution, the time at which a significant change in color occurred was observed on the stopwatch. If the solution was not discolored within 60 seconds, the ac- The reaction mixture contained 0.5% if the solution decolorized for 45-5 seconds. In 20-5 seconds, solutions containing 1% active chlorine were decolorized.

For an active chlorine content greater than 2%, the time required to decolorize is less than 20 seconds.

Example 4 g of p-cresolsulfophthalein was dissolved in 50 ml of acetone and made up to 100 ml with water. The prepared solution was impregnated with 10 x 50 mm Whatman 1 strips of chromatography paper so that 1 g of paper contained 5 mg of reagent. Strips of paper impregnated with p-cresolsulfophthalein were immersed in solutions

240 786 calcium hypochlorite containing 0,2 to 5% active chlorine in 0,2% increments at 10, 20, 30, 40, 50 and 60 ° C «Three parallel measurements were carried out for each temperature the paper bleached from the moment of immersion · The bleaching rate of the indicator paper was found to increase with temperature · Solutions containing more than 5% active chlorine bleached the paper in less than two seconds *

Example 5

A 2% acetone solution of 3? 3 ** 5? 5'-tetrabromo-m-cresolsulfophthalein was prepared. 10 x 50 mm strips of chromatographic paper were thus impregnated to yield 5 mg of reagent per g of Whatman 1 paper. The prepared, dried indicator papers were immersed in solutions of benzoetolorsulfonamide in 1,2-dichloroethane containing 0.5; 1.0 and 3.0% active chlorine ·

At 20 ° C, the time to decolour the papers was measured. Three parallel replicates were chosen for each test. Solutions containing 1% active chlorine bleached the indicator paper within 40 seconds.

The use of color solutions and impregnated cresolsulfophthalein papers allows detection and determination of active chlorine in the solution. Knowing the dilution and the time it takes to discolour the indicator paper or solution, it is possible to determine the active chlorine content and thus its quality with an accuracy of 0.2%.

The indicator system of the present invention allows the quality of solutions containing active chlorine to be determined quickly and easily. This also improves the efficiency of the work process while reducing material costs.

Claims (1)

SUBJECT OF THE INVENTION Method for the detection and determination of active chlorine, characterized in that the analyzed sample containing active chlorine is reacted with cresolsulfophthalein in solution or on a carrier, for example papers, and the presence and concentration of active chlorine is determined by color change and time required. in the sample.