SU785695A1 - Phosgene determining method - Google Patents

Description

t

This invention relates to methods for the determination of phosgene in solutions.

There is a known method for the determination of phosgene in a technical product, which is based on the reaction of 5 phosgene with sodium iodide with the release of free. titrate the latter with aqueous sodium sulfate solution l.

The disadvantages of this method are the laboriousness and the use of a large number of reagents, of which gzhetton, calcium sulphate, sodium iodide must be specially dehydrated. At the same time, impurities of 5 chlorine and hydrogen chloride interfere with the determination of the main initiative. In addition, this method is not suitable for the analysis of phosgene solutions with a low content of the latter. 2Q

A known method for the determination of phosgene in the air of permeable plants is based on the treatment of phosgene with norsulfazole and sodium nitrite followed by photocolorimetric-25 of the obtained colored solution 1.

The disadvantage of this method is its low accuracy (30–50 rel.%) And unsuitability for determining phosgene in DL.

solvent, do not mix with water.

The purpose of the invention is to increase its accuracy and expand its use.

This goal is achieved by the described method, which consists in the fact that a sample of the analyte is treated with a solution of ammonia in aliphatic alcohol, followed by treatment of the obtained solution of p-dimethyl acyunobenzaldehyde in the presence of sulfuric acid and photocolorimetry the obtained colored solution.

In the described interaction of phosgene with ammonia, the reaction proceeds at a noticeable rate, while with an aqueous solution of ammonia, even after preliminary mixing of the analyzed solution on a mechanical rocker, the reaction does not end. it is in 5 days.

The solubility of ammonia in alcohols is 13, 10.10.9 vol. %, respectively, for methyl, ethyl, propyl and isopropyl alcohols.

When phosgene interacts with ammonia, urea is formed, which is determined by a method based on the ability of urea, when interacting with paradimethylaminobenzaldehyde, to form colored compounds in an acidic medium.

The method can be used to determine phosgene in solvents that do not contain in the composition of the molecules of the groups that can give colored compounds in the interaction with paradimethylaminobenzaldehyde (DABA) in an acidic medium. The range of such solvents is very wide: aliphatic hydrocarbons (heptane hexane, etc.), aromatic hydrocarbons. (benzene, toluene, xylene, etc.), alcohols (methyl, ethyl, propyl, isopropyl), halogen derivatives of hydrocarbons (carbon tetrachloride, chlorobenzene, dichlorobenzene, etc.),

Example. In a glass vessel with a capacity of 30-40 ml with a tube of thin section 14 or 19, 4 ml of a saturated ammonia solution are added and a pipette of 1 ml of a phosgene solution of unknown concentration is added. Quickly and tightly close the stopper vessel and hold the resulting solution for at least 10 hours. Then, 1 ml of the solution obtained (solution A) is added to a suitable container, 5 drops of 46% H / Oc and 4 ml of DABA solution are added. isopropyl alcohol with a concentration of 40 g / l and 3 ml of a solution of concentrated sulfuric acid in dimethylformamide, taken in an acid: DMF ratio of 5: 45. After 5 min, the optical density of the resulting solution was measured (if precipitated, filtered) on a spectrophotometer SF-4A in a cuvette with a layer thickness of 1 s at the maximum wavelength (430 nm). As

a comparison solution using a mixture of 4 ml of the DABA solution and 3 ml of the sulfuric acid solution indicated above. From the obtained value of D and the calibration graph (tangent of the angle of inclination by the calibration curve 8.02 + 0.19), the desired concentration of phosgene in the solution is calculated in relation to Beer's law.

When calculating the calibration graph, weighed amounts of phosgene (0.060, 2 g) in glass ampoules, the solution contents of the ampoules in a 25 ml volumetric flask with an appropriate solvent.

The determination error does not exceed S 5 rel.%. The sensitivity of the analysis procedure is 0.012 mol / l.

Claims (2)

1. Franck 3., Franz P., Varnke V. Chemistry poisoned substances. M., Himi, 1973, p. 113. 2. Peregud E.A., Germet E.V. chemical analysis of industrial air. L., Himi, 1970, with. 76 (prototype).