Patent GB-377720-A (GB)
Title: Improvements in the treatment of magnesite for the production of fertilizers
IPC: C05B7/00
Filed: 1931-02-28
Abstract: Magnesite, previously roasted to 600-1200 DEG  C. and preferably pulverized, is mixed with 50-70 per cent phosphoric acid or with concentrated phosphoric acid and ammonia or an ammonium salt, preferably ammonium phosphate, to produce magnesium phosphate or magnesium ammonium phosphate respectively, the product obtained being of a dry pulverizable nature, utilizable as such as a manure.  A temperature rising to 70-90 DEG  C. is specified in the production of a mixture of di- and tri-magnesium phosphates.  The phosphoric acid may be replaced by sulphuric acid and phosphate of lime, the production of magnesium phosphate or magnesium ammonium phosphate being thus combined with that of superphosphate.  A reaction temperature of 50-80 DEG  C. is specified.  In an example, concentrated phosphoric acid, pulverized roasted magnesite, and ammonium phosphate are introduced into a normal preparation of superphosphate to produce a mixed manure.  The Specification as open to inspection under Sect. 91 (3) (a) comprises also the treatment of magnesium rocks generally, dolomite being additionally specified. The mineral is crushed, calcined or hydrated, or both, and subjected to the action of acids such as hydrochloric acid, nitric acid, nitrous acid, sulphuric acid, or phosphoric acid, either concentrated or as residual mixtures.  Reference is also made to the use of chlorine and residual ammoniacal waters.  When dilute acids are employed, the product is filtered and dried.  When raw magnesium rock is used, reaction is effected in the hot; when calcined, it may be dissolved in the cold.  In examples, (1) crude dolomite is treated with sulphuric acid to precipitate the lime as calcium sulphate. Phosphoric acid and an ammoniacal solution are added to precipitate magnesium ammonium phosphate, the solution of ammonium sulphate remaining being then concentrated; (2) to a mixture of powdered roasted magnesite, phosphoric acid, and ammonium phosphate, calcium or magnesium silicate is added to produce a manure; (3) roasted magnesite is dissolved in 50 per cent nitric acid, and the solution crystallized.  The product is dried so that it does not contain more than two molecules of water of crystallization.  This subject-matter does not appear in the Specification as accepted.ALSO:In treating magnesite, previously roasted to 600-1200 DEG  C. and preferably pulverized, with concentrated phosphoric acid with or without ammonia, or an ammonium salt, preferably ammonium phosphate, the phosphoric acid may be replaced by sulphuric acid and phosphate of lime, the production of magnesium phosphate or magnesium ammonium phosphate being thus combined with that of superphosphate.  A reaction temperature of 50-80 DEG  C. is specified.  In an example, concentrated phosphoric acid, pulverized roasted magnesite, and ammonium phosphate are introduced into a normal preparation of superphosphate to produce a mixed manure.  The Specification as open to inspection under Sect. 91 (3) (a) comprises also the treatment of magnesium rocks generally, dolomite being additionally specified.  In an example, to a mixture of powdered roasted magnesite, phosphoric acid and ammonium phosphate, calcium or magnesium silicate is added to produce a manure.  This subject-matter does not appear in the Specification as accepted.