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Hydrolysis

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Description of key information

The test substance hydrolysed very rapidly (t½ < 2 minutes) at pH 4, pH 7 and pH 9 and indicates chloride, sulphite and sulphate as hydrolysis product.

Key value for chemical safety assessment

Half-life for hydrolysis:
2 min
at the temperature of:
23 °C

Additional information

The hydrolysis behavior of the substance was determined according to the OECD guideline 111 (Hydrolysis as a Function of pH). Since it is known that the hydrolysis of the substance is very fast, the test was determined at pH 4, pH 7 and pH 9 at room temperature (instead of at 50 ° C). The hydrolysis behaviour was monitored by ion chromatography analysis with conductivity detection. The substance shows rapid and complete hydrolysis confirmed by the chloride detection. The hydrolysis test samples were directly analyzed after preparation. The overall degradation of the substance observed with the determination of the content of the hydrolysis product chloride at room temperature is higher than 90 %. Additionally the expected hydrolysis products sulphite and sulphate could be determined. The expected hydrolysis product sulfur dioxide could not be detected by ion chromatography. The half-life time for all pH values was t½ < 2 minutes.

The kinetics of the hydrolysis of thionyl dichloride in the gas phase was investigated. The hydrolysis rate is depending on the humidity. The higher the relative humidity, the faster is the reaction. The tropospheric lifetime of the substance due to hydrolysis was of only a few minutes. Derived from the decay constants, half-lives of 1.4 minutes (74% relative humidity) to 5.9 minutes (28% relative humidity) at 20°C are calculated. HCl and SO2 as hydrolysis products were identified and quantified.

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