This is a whitish crystalline salt manufactured from natural deposits in the German potash mines. As a manure, the best samples contain 98 per cent of sulphate of potash, equal to over 52 per cent of pure potash. Inferior samples contain about 90 per cent of sulphate of potash, equal to 48 per cent of pure potash. The double sulphate of potash magnesia, which contains a good deal of magnesium sulphate, is often called sulphate of potash, but it is inferior in potassic value. It contains about 50 per cent of sulphate of potash, equal to 27 per cent of pure potash.

Sulphate of potash has gained a great name as a potato manure. It is considered to produce tubers of better quality, but this would depend largely upon the character of the soil.