When six organophosphorus compounds of P=S type (Parathion, Methylparathion, Malathon, Ekatin, Baycid and Sumithion) were treated with the oxidative reagent (bromine water), the inhibition of cholinesterase activity by these phosphorus compounds was markedly increased. Similar tendency was found in the case of thiol and sulfoxide type compounds. When these oxidized organophosphorus compounds were present, the reactivation rate of cholinesterase activity by PAM was elevated significantly. In contrast to these inhibitors dimethoate did not show the increased inhibition of cholinesterase activity by the oxidative treatment and in this case the effectiveness of PAM was also unchanged.

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The alkaline hydrolysate of nine organophosphorous systemic insecticides were fractionated by means of paper chromatography and paper electrophoresis. The nine insecticides were Systox, Improved Metasystox (O, O-dimethyl-S-2 (ethylthio) ethyl phosphorothioate), Ekatin (O, O-dimethyl-S-2-(ethylthio) ethyl phosphorodithioate), Thimet (O, O-diethyl-S-2-(ethylthio) methyl phosphorodithioate), Mesyston (O, O-dimethyl-S-2-(ethylsulfoxy) ethyl phosphorothioate), Dimethoate (O, O-dimethyl-S-(N-methylcarbamoyl) methyl phosphorodithioate), Phosdrin (O, O-dimethyl-O-1-methoxycarbonyl-1-propene-2-yl phosphate), Endothion (O, O-dimethyl-thiophosphorylmethyl-2-methoxy-5-pyrone-4) and Pestox-3 (octamethyl pyrophosphoramide). Some of the main hydrolysis products of each of the insecticides were characterized and identified by comparison with authentic specimens. The results obtained afford a systematic method available for the identification of any one of these insecticides.

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(1) The reaction of Gries Romijin reagent with NO₂^- ion was accelerated by adjusting the pH of reaction mixture at 4.0. At this pH, the color developed was stable. The estimation of micro-amounts (0.01∼0.4 ppm) of NO₂^- ion was performed with a good sensitivity. (2) NO₃^- was quantitatively reduced to NO₂^- with Mn²⁺ in ammonia alkali solution and reacted with G.R. reagent at pH 4.0. The estimation of 0.02∼0.6 ppm of NO₃^- was thus performed. Since coexisting NO₂^- is stable in the reduction conditions, NO₃^- and NO₂^- in one mixture can be estimated separately.

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(1) The mercury content in the urines of cases of acute phenylmercuric acetate poisonings was found about 10∼15 times higher than that of the normal. (2) The urine of a patient of chronic poisoning by methyl mercuric thioacetamide contained mercury in a similar amount to that of normal. But in the blood and hair, the amount of mercury detected was about 3 and 40 times larger than normal respectively. (3) Among the mercury contents in the urine, blood and hair of cases of poisonings, that in the hair was found remarkably high even after medical treatment. (4) From these observations, the analysis of mercury contents in hair was found important in the case of chronic poisoning by organic mercurial compounds.

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