It is put on the market as muriate of potash, sulphate of potash, kainite, which contains salt as an impurity, and in other impure forms.

To the substances used for treating brewing liquors already mentioned we may add kainite, a naturally deposited composite salt containing potassium and magnesium sulphates and magnesium chloride.

The crude salts, kainite and sylvinite, and the muriate contain chlorine and are not considered good for potatoes and tobacco as the chlorine lowers the quality of these products.

Acid phosphate and kainite added to the manure may pay handsomely.