Abstract: Langbeinite and kieserite are beneficiated in a flotation process in which separation of ore particles is conducted in a froth flotation process with a magnesium chloride brine containing at least 20 moles MgCl.sub.2 per 1000 mols H.sub.2 O. Said brine is maintained at a pH below about 3.5. The preferred flotation agent is a combination of a fatty acid amine (preferably tallow amine) and an organic acid, either oleic or sebacic acid, in an approximate ratio of 2 to 4 parts amine to 1 part oleic or sebacic acid, and preferably in an amine-oleic or amine-sebacic acid ratio of about 3:1. Flotation is preferably conducted in two stages wherein the sink product from the rougher flotation contains langbeinite above about 95% concentration which is relatively free of kieserite and the froth from the rougher flotation is passed to a second "cleaner" flotation step where the kieserite is further concentrated to above about 75% kieserite.

Abstract: Potassium sulfate (K.sub.2 SO.sub.4) is prepared by contacting potassium chloride with an aqueous solution containing potassium bisulfate at a temperature of about 65.degree.-110.degree. C., cooling the solution and permitting the potassium sulfate to crystallize from solution.