Abstract
This paper describes some modifications of the distillation method for the determination of total cyanide content in soil. Generally, the total cyanide content in soil has been determined by a sediment survey method, which is based on JIS K 0102 in Japan. However, in the recovery test of spiked ferrocyanide in the simulated soil, the recovery ratio of total cyanide was less than 50% by this method. In order to improve the distillation method, some acids and some addition reagents, which were described in ISO, standard methods and JIS, have been examined. As a result, a distillation method using phosphoric acid (20 mL), copper chloride (89 g L−1, 10 mL) and tin chloride (500 g L−1, 5 mL) for the sample (10 g) has been recommended. This method (NSOF method) could recover more than 90% of the total cyanide from spiked ferrocyanide, ferricyanide, Prussian blue, copper cyanide (I) and potassium cyanide in the simulated soil samples. In addition, this method was applied to three real contaminated soil samples. As a reason of the low recovery ratio of total cyanide by the sediment survey method, we confirmed that Prussian blue was formed by the react with ferrocyanide and ferrous or ferric ions in soil under the phosphoric acid condition.
