return-alkali

Century Dictionary and Cyclopedia

1. n. In the manufacture of prussiate of potash (see prussiate) on a large scale, the salt obtained from the residual mother-liquor, which, after the lixiviation of the calcined cake, the second crystallization, and second concentration, yet contains about 70 per cent. of potassium carbonate. The salts crystallizing out are also called blue salts. They are utilized by mixing them with the charge for another calcining process.