Method and apparatus for preparing a calcium thiosulfate solution.

A process for preparing a calcium thiosulfate solution comprising: providing a suspension of calcium hydroxide; adding sulfur to the calcium hydroxide slurry and reacting sulfur with calcium hydroxide to form a reaction mixture; cooling the reaction mixture, if necessary, to a temperature suitable for oxidation; adding to the reaction mixture an oxidant and reacting under conditions sufficient to form calcium thiosulfate; and recovering the calcium thiosulfate solution.