Patent GB-781504-A (GB)
Title: Improvements in or relating to process for the manufacture of defluorinated phosphatic materials
IPC: C05B1/02
Filed: 1955-01-27
Abstract: Defluorinated phosphatic material containing phosphate in the ortho phosphate state or an equivalent state such as in beta tricalcium phosphate which is assimilable by animals, is prepared by mixing comminuted tricalcium phosphate with sulphuric acid, calcining the mix at a temperature below fusion and high enough to evolve fluorine, normally between 1000 DEG  and 2700 DEG  F., and reacting the defluorinated acid mix with phosphoric acid and drying the reacted mixture under conditions which prevent any substantial production of pyrophosphate.  The calcining treatment is preferably effected in the presence of heated gas currents containing water vapour.  The phosphate rock is preferably ground to a particle size of 90-100 mesh (U.S. standard) and mixed with sulphuric acid in a proportion of 1000 parts of rock to 450-750 parts by weight of 98 per cent sulphuric acid during which mixing some fluorine is volatilized.  The mixture is thereafter calcined and after calcination generally has a P2O5 content of 30-42 per cent.  Phosphoric acid in amounts sufficient to produce, for example, 18 or 20 per cent elemental phosphorus content is then added, generally 200-500 parts of phosphoric acid being required per 1000 parts of the defluorinated mix.  It is preferable to pre-wet the defluorination mix with water before adding concentrated phosphoric acid but the water content should be limited to 15-20 per cent.  The mixture is then dried at 90-150 DEG  C., preferably 105-130 DEG  C., and if desired, granulation may be effected prior to such drying.  Examples are given, the products of which analysed 18.1 per cent elemental phosphorus and 1.4 per cent moisture, and 19.24 per cent elemental phosphorus and 1.6 per cent moisture respectively.  An example compares the biological value of the product of the invention with beta tricalcium phosphate and a calcined phosphate rock-sulphuric acid mix which value is assessed by feeding chicks with a basic mix consisting of corn starch, blood fibrin, gelatine, ground cellulose, a solubilized dry concentrate containing the alcohol insoluble fraction of liver, and hydrogenated vegetable fat to which has been added sufficient of the above-mentioned phosphate sources to provide a 0.25 per cent phosphorus content.ALSO:Defluorinated phosphatic material containing phosphate in the ortho-phosphate state, or an equivalent state such as is found in beta tri-calcium phosphate, and so assimilable by animals, is prepared by mixing comminuted tricalcium phosphate with sulphuric acid, calcining at a temperature below fusion and high enough to evolve fluorine, usually between 1000 DEG  and 2700 DEG F., reacting with phosphoric acid, and drying under conditions which prevent formation of pyrophosphate.  An example is concerned with comparison of the biological value of products of the invention, beta tricalcium phosphate and a calcined phosphate rock-sulphuric acid mixture, chicks being fed with a basic diet consisting of corn starch, blood fibrin, gelatine, ground cellulose, a solubilized dry preparation of the alcohol insoluble fraction of liver, and hydrogenated vegetable fat, to which is added sufficient of the phosphate to provide a 0,25 per cent phosphorus content.