GB908017A - Improvements in or relating to the production of non caking common salt - Google Patents

Abstract

The caking tendency of cubic crystalline Na Cl is reduced by adding to it one or more compex iron compounds, wherein the iron is bonded through one or more oxygen atoms with a saturated aliphatic compound having 3 to 6 C atoms and containing two or more COOH groups together with one or more OH groups; tartaric, citric, gluconic acids are specified. The complexes may contain other anions in the molecule to render it neutral, for example alkali metal or ammonium ions. Preferred are ferric ammonium citrate, gluconate or tartrate. The amount used is greater than ,0002% by weight on dry Na Cl and depends on the particle size; thus for 0,3 mm. cubes the preferred range is ,0001-,002%. In order to obtain a free flowing product other customary salt additives, e.g. Mg CO3 may also be added. The complex iron salt may be added to the Na Cl by either spraying a solution of the additive on to damp or dry salt separated from its mother liquor, or by the introduction of the additive into the mother liquor containing the solid Na Cl prior to separation. The two examples refer to spraying dry salt with ammonium ferric citrate. The Provisional Specification also refers to the following classes of anticaking additives. M5[V (CN)5 NO] M3[Cr (CN)5 NO] M4[Mo(CN)5(OH)2NO] M6[Co(CN)5]2 where M is an alkali metal (including ammonium) ion of which K5[V(CN)5 NO.H2O] is the subject of an example.