Preparation of Cadmium Oxalate.
A piece of cadmium was dissolved in pure nitric acid. On carefully evaporating the solution cadmium nitrate was obtained. Twenty-five grams of the nitrate were dissolved in 750 c.c. of redistilled water. Somewhat less than an equivalent of the oxalic acid was dissolved in an equal volume of water, and slowly added to the solution of the nitrate with constant shaking. A little less than an equivalent of oxalic acid was used to avoid any tendency to form acid oxalates. Cadmium oxalate was precipitated on standing a few minutes as a white crystalline compound, well adapted to washing. The oxalate was filtered off and washed until the wash water was free from all traces of nitric acid. It was then washed ten times with water which had been twice redistilled and dried in an air-bath for twenty hours at 150°C.
The arrangement of the crucibles which were weighed was in all respects like that in the preceding method.