Abstract
Improvements have been made on the spectrophotometric determination of nickel by Sandell's method and a method for determining exchangeable nickel in soils without separation has been established. The main point of improvement is the addition of a stabilizing agent for the 1:2 nickel-dimethylglyoxime complex initially formed by the ammonia-bromine method. The authors found that the color intensity of the 1:2 complex did not vary within 3 hours at 20°C by the addition of ammonium acetate or a mixture of ammonium acetate and citric acid before coloration (Fig. 1 and Fig. 2). The absorbance at 445mμ was not affected by the presence of considerable amounts of metallic ions except for copper (Table I), and, therefore, this method is suitable for the determination of exchangeable nickel in a number of soil samples. Comparing with the Sandell's method, the recommended method was more accurate (Table II). Determination of nickel in plants grown on the serpentine soil was possible provided that the content of copper was not so high (Table III).
