<Original Papers>On the Solubility Products of Ferric, Calcium and Magnesium Arsenates

The arsenic problem in nonferrous smelters should be solved as soon as possible. The present work was undertaken from the viewpoint of hydrometallurgical treatment of arsenic-containing by-products. Arsenic can be removed as some insoluble arsenates from leached solutions or waste waters. On removal of arsenic from solutions, therefore, the solubility product of arsenates must be taken into consideration. Thus the solubility product of ferric, calcium and magnesium arsenates has been determined experimentally by mixing these arsenates with various pH solutions for 24 hours and then determining both metallic and arsenic concentrations in solutions. The experimental results are as follows : K_=10^, K_=10^, K_=10^ at 25℃. The solubility product of ferric arsenate was also determined by adding a ferric salt solution to the aresenic acid solution and by determining the arsenic and ferric concentrations after 1 hour. The arsenic concentration decreased with an increase in ferric ion concentration. The solubility product of ferric arsenate was nearly the same as that when dissolving ferric arsenate. When adding the ferric salt solution, therefore, the arsenic concentration in solution is controlled by the solubility product of ferric arsenate up to pH 3