青酸化合物より揮發する青酸量と水素イオン濃度との關係 (第4報)

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抄録

Sodium nitroprusside was added to three kinds of buffer solution, i.e. phosphoric acid-sodium phosphate, citric acid-sodium hydroxide, and tartaric acid-sodium hydroxide, and quantities of free hydrocyanic acid liberated were measured at 15°, 37°, 60° and 100° at varying pH. No free hydrocyanic acid was detected at 15° in any of the buffer solutions: the highest concentration of the liberated HCN was 0.0008 per cent at 37°, 0.0368 per cent at 60° and 1.3576 per cent at 100°.
The amount of HCN liberated from sodium nitroprusside varies considerably with the compositin of the buffer; with the tartaric acid-sodium hydroxide buffer solution, the peak amount of HCN librated at 60° is witnessed at pH 3.5 and that at 100° is attained at pH 5.5-6.8. This is considered to be due to the specific effect of the tartrate ion, suggesting that the selectivity exhibited by each buffer solution with regard to HCN liberation should be taken into due consideration.
The amount of HCN liberated from sodium nitroprusside solution is thus so small in the neighborhood of human temperature (37°) that the toxicity of the solution is of no significance. It is pointed out, howeuer, that the toxicity of the liberated HCN should be taken into account at temeratures above 60° depending on the time of contact and the presence of catalyzer.