It is usually made by distilling tartaric acid with potassium bisulphate at about zoo-250° C., the crude product being afterwards fractionated.
By acting upon a solution of sodium hyposulphite with potassium bisulphate, Gernez (Compt.
By fusing the mineral, very finely powdered, with six times its weight of potassium bisulphate in a platinum crucible, then extracting the melt with cold water and boiling the filtered solution for a long time.
Fusion with an alkaline bisulphate converts the silver into the sulphate, which may be extracted by boiling with sulphuric acid and then with water.
The acid sulphate, NaHSO 4, also known as bisulphate of soda, is obtained as large asymmetric prisms by crystallizing a solution of equivalent quantities of the normal sulphate and sulphuric acid above 50°.