GB848328A - Improved salt crystals - Google Patents

Abstract

Non spherical crystals of sodium chloride of irregular shape or of sharp-edged cubic or other polyhedral shape of 0.8 mm. to 2 mm. linear size and a bulk density when poured exceeding 0.7 gm./cc. are prepared by evaporating brine under reduced pressure and allowing the salt crystals to grow for a sufficient period in the body of the supersaturated brine solution, wherein there is added to the brine in an amount less than that required to secure the formation of dendritic crystals of bulk density below 0.7 gm./cc., a water soluble compound having the formula A(MX6), where A is a cation and MX6 is a complex anion in which a metal M is associated with six not necessarily identical atoms or groups X, or a polyphosphate formed by reaction of ammonia with phosphorus pentoxide (e.g. victamide), or potassium silico tungstate, or a polyphosphate, or ethylene diamine tetra acetic acid, or sodium diethyl dithio carbamate, or ammonium dihydrogen phosphate, or a soluble bismuth salt, or extract of Carragheen Moss, or a cellulosic, or alginic hydrolysed homopolymeric longchain organic compound containing carboxylic acid side groups or a salt thereof. Specified substances include K4Fe(CN)6; Na3[Fe(CN)5CO]; ammonium polymethacrylate; sodium carboxymethyl cellulose; sodium alginate; hydrolysed polyacrylonitrile; and sodium hexametaphosphate. The brine may be freed of calcium and magnesium and its pH adjusted to 8 or more prior to evaporation. The evaporation may be conducted in one vessel and the supersaturated brine then flows through a bed of crystals in another vessel. Specifications 667,101 and 779,742 are referred to.