SU1310718A1 - Method of quantitative determining of methyl mercaptan in water - Google Patents

Abstract

This invention relates to analytical chemistry, in particular, to the determination of methyl mercaptan in water, which can be used in the chemical field. The goal is to increase the detection sensitivity and reduce the analysis time. The determination of methyl mercaptan is carried out by dissolving 0.1567 + 0.0001 g of lead methyl mercaptide in a 5% aqueous solution of mercury acetate. The resulting solution is acidified with hydrochloric acid and an inert gas is passed through it at a temperature of 60-70 ° C and a gas flow rate of 300-400 ml / min. Capture lead in the absorption tube with a mixture of mercury acetate with glycerin. Mercury methyl mercaptide is eluted with water and reacted with hydrochloric acid S, K-dimethyl-para-phenylenediamine in the presence of ferric chloride. The optical density is measured at 496 nm. This method makes it possible to increase the detection sensitivity by a factor of 5,000 and reduce the detection time by a factor of 12 in comparison with the known method. 1 dw., 2 tab. WITH

Description

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The invention relates to analytical chemistry and can be used to determine methyl mercaptan in multicomponent, colored aqueous solutions at the level of the maximum permissible concentration (0.0002 mg / l), for example, in waste water of pulp and paper industry.

The purpose of the invention is to increase the detection sensitivity and shorten the analysis time.

Figure 1 shows a setup diagram for implementing the method.

The apparatus comprises a stripping vessel 1 with a cap 2, an absorption tube 3 and a thermostat 4.

The method is carried out as follows.

Build a calibration graph. On an analytical balance in a glass tube, we weigh a portion of methyl mercapti and lead brand x, 4, equal to 0.1567 + 0.0001 g. Then it is quantitatively transferred into a 100 ml volumetric flask and dissolved in 5% - A mercury acetate aqueous solution of the grade of ch.d.a, the result is a water-soluble complex of these salts. Next, 10 ml of the obtained water-soluble complex is pipetted, transferred to a 1000 ml volumetric flask, and made up to the mark with water. As a result, 1 ml of the obtained standard solution corresponds to a content of 5 μg of methyl mercaptan CHjSH,

2.0 ml of the standard solution is pipetted into the 1000 ml stripping vessel 1 and the volume is made up to 1000 ml with distilled water. Then the pH of the resulting solution is adjusted to 1 with concentrated hydrochloric acid and the vessel is tightly closed with a lid 2, in which the absorption tube 3 is fixed with a liquid film absorbent. Next, the stripping vessel is placed in a thermostat 4 at 70 + 1 C and turns on the inert gas supply (nitrogen, argon) to the vessel with a flow rate of 400 mg / min. As a result, lead methylmercaptide is quantitatively destroyed with the formation of methyl mercaptan gas, which in turn is transferred by the flow of inert gas from solution to the liquid film sorbent where it is trapped on the film of mercury acetate solution and glycerol to form methyl mercapti

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yes mercury After 30 minutes, the absorption tube is removed, mercury methyl mercaptide is eluted from it with water and the mercaptide is reacted with hydrochloric acid K, K-dimethyl-para-phenylenediamine in the presence of ferric chloride. The optical density of the resulting solution was measured at 496 nm (light filter No. 5 on FEC-56 M) in a cuvette with a layer length of 2 cm relative to the zero solution. A photometric analysis yields a value. optical density of 0.1. Analyze in a similar way the standard solution of methyl mercaptide lead, taken in the amount of 0.2; 0.4; 1.0; four; 6; eight; ten; 20 ml is obtained on the calibration graph of the point, which corresponds to the content of methyl mercaptan in the initial solution, equal to 1, 2, 5, 20, 30, 40, 50, 100 µg, and build a calibration graph (figure 2), which shows a linear the dependence of the content of methyl mercaptan in the model solution on the optical density of the solution corresponding to this content.

Example 1. Methyl mercaptan is determined by the proposed method in a model solution with a concentration of 0.0457 mg / l with temperature values of 55, 60, 65, 70, 75 C, and gas flow rates of 200, 300. 350 400, 500 mg / min. The data analysis are presented in table.1.

Example 2. Methyl mercaptan is determined by the proposed method in industrial wastewater of the Baikal Pulp and Paper Mill at 70 ° C and a gas flow rate of 300 ml / min. The analysis data are presented in table. one,

PRI me R 3. The determination of methyl mercaptan was carried out by a known prototype method in a model solution with a concentration of 10 mg / l at 100 ° C and a gas flow rate of 80 ml / min. The data analysis are presented in table.1.

EXAMPLE 4 Methyl mercaptan is determined by a known method in model solutions with concentrations of 5, 10, 15, 20, 25 mg / l and by the proposed method in model solutions with concentrations of 0.002; 0.0457; 0.2; one; 5 mg / l at a gas flow rate of 350 ml / min. The analysis data are presented in table. 2

The temperature of the methyl mercaptan stripping was determined, followed by trapping it on the liquid film sorbent and the range of values of the gas flow during the stripping, which made it possible to achieve a degree of concentration of the analyzed component equal to 2000 times. The established temperature range for the stripping process is determined by the minimum analysis time.

At a temperature of less than 60 ° C, the time of stripping increases; more than 70 ° C, the maximum degree of stripping is 10; the detection limit of methyl mercaptan is

water is 0.002 mg / l, and the sensitivity of the known method is 10 mg / l.

Thus, the proposed method (5 makes it possible to reduce the detection limit by 5000 times and reduce the detection time by 12 times in comparison with the known method.

dramatically increases the content of water vapor in the gas phase during stripping, which leads to choking of the liquid film sorbent and loss of the analyzed component during the subsequent

capturing.

Claims (1)

The established range of values is 20 The gas flow inventive formula for stripping provides the maximum degree of stripping with the method of quantitatively determining the minimum analysis time. When methyl mercaptan is dissolved in water by passing a gas of less than 300 ml / min to increase the gas through the sample being analyzed, the time of analysis is increased, and an increase in methyl mercaptan capture from the after-flow of gas over 400 ml / min results in loss of the component being analyzed. breakthrough through the absorption tube with a liquid film sorbent. All this in the Combination30 analysis, the transmission of gas is carried out at a photometric end of the analysis at a temperature of 60-70 and the gas flow results in a sensitivity increase of 300-400 ml / min, the trapping is carried out on Analysis of the data presented in the liquid film sorbent - a mixture of table. 1 shows that in the preparation of mercury acetate with glycerin followed by its photometric determination, characterized in that, in order to decrease the detection sensitivity and reduce the time method at a temperature of less than 60 ° C, the analysis time increases, and Proposed Example 1 experiments, 1 2 3 counter, 4 at temperatures above 70 ° C, the analyte is lost due to flooding of the absorption tube. From tab. 1 also shows that the analysis time for the proposed method is reduced by I2 times as compared with the known method. Analysis of the data presented in Table 2 shows that the achieved The invention The method of quantitative determination of methyl mercaptan in water by passing a gas through an analyzed sample, trapping methyl mercaptan from the post-analysis, passing the gas at a temperature of 60-70 and a gas flow rate of 300-400 ml / min, trapping is carried out on photometric determination thereof, characterized in that, in order to increase the detection sensitivity and reduce the time 35 by elution of the resulting mercaptide, I Table 1 0.5 2000 0.0426 0.5 0.0428 70 75 0.5 0.5  0,0450 0,0300 Ways Continuation of table 1 table 2 Gas Editor A.Revin Compiled by S. Hovanska Tehred I.Popovich Proofreader L. Patay Order 1884/40 Circulation 777 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4