28 августа, 2015 
Pokraskin Solutions of sodium sulfide are normally made from sodium sulfide flakes (Na2S. H2O). If lithopones are required, a solution of barium sulfide is also necessary. The latter can be purchased as “black ash”, which owes its name to a gray appearance, having been made from the reduction of barium sulfate with carbon. It is difficult to handle, and not as soluble as sodium sulfide. The solutions should be kept warm to prevent crystallization. Sodium sulfide solution is also required to dissolve selenium for the production of cadmium reds.
3.4.5
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