Insecticide Determination. II. Colorimetric Determination of Dimethyl 1, 2-Dibromo-2, 2-dichloroethyl Phosphate (Dibrom).

Abstract

A colorimetric method for the determination of DDVP is modified to adapt for the determination of Dibrom, which based on the color complex formed between Dibrom and acetone in the presence of alkali. The values obtained from this method showed good agreement with the values from the infrared absorption spectral method. Periodical change of 5% Dibrom emulsifiable concentrate was studied at 100, 70, 60, and 50° by this colorimetric method, and statistical treatment was made to presume the days required until 10% reduction at 30, 25, and 20°. Experiments were further made to see whether these values would agree when the concentrates were maintained at room temperature. From this result, the days required until 10% reduction at room temperature were 1.5, and 3∼4 months in the emulsifiable concentrate containing 5% of epi-chlorohydrin and the one not containing it, respectively. These values showed good agreement with the values obtained from the statistical treatment. epi-Chlorohydrin has no stabilizing effect on Dibrom or rather promotes decomposition. Dibrom in the emulsifiable concentrate is fairly stable when nonionic emulsifier alone is present, but undergoes fairly rapid decomposition in the presence of anionic emulsifier alone.