Abstract
Successive colorimetric determination of Co, Cu and Ni has been presented. Cobalt is not extracted into dilute nitric acid from the solvent containing its diethyldithiocarbamate, while other metal chelates are extracted. Copper has a greater chelate formation constant with the carbamate than Ni and Pb, and gives selectively a substitution reaction with Pb in the complex in the solvent, while Ni does not. The recommended procedure applying to the analysis of these metals in aluminum metal and aluminumuranium alloy is as follows;
One gram of sample was dissolved in hydrochloric and nitric acids mixture. The pH was adjusted to 8.59.0 with ammonia after adding 15 ml of 50% citric acid solution. It was transferred into a separatory funnel, and 3.0 ml of 2% sodium-diethyldithiocarbamate solution was added. The solution was shaken vigorously with 10 ml of benzene for 5 min and the aqueous layer was discarded. Fifteen ml of HNO3 (1+10) was added into the separatory funnel and the mixture was shaken vigorously. This procedure was repeated three times. All layers of the nitric acids (Solution A) were stored into beaker and used for the determination of Cu and Ni. The amount of cobalt was determined from the absorbance of the benzene layer at 325 nm. The pH of the solution A was adjusted to 8.59.0 with ammonia after adding 2 ml of 50% citric acid solution. The solution was transferred into a separatory funnel and shaken vigorously with 5 ml of lead diethyldithiocarbamate chloroform solution for 5 min. The amount of copper was determined from the absorbance of the chloroform layer at 435 nm. One ml of 2% dimethylglyoxime was added into the separatory funnel which contained the aqueous solution after the determination of the copper. The solution was shaken vigorously with 5 ml of chloroform for 3 min. The amount of nickel was obtained from the absorbance of the chloroform layer at 325 nm. The limit of determination for cobalt and copper was 1 μg and that for nickel was 2 μg.
