128 PHOSPHATIC MANURES 



are weighed into a porcelain basin, mixed with 30 c.c. 

 of water, and then 10 c.c. of concentrated sulphuric acid 

 gradually added, with constant stirring. If the mixing 

 has been judiciously carried out, the heat produced 

 evaporates any excess of water, and the residual material 

 will form a solid but slightly damp mass of " vitriolised" 

 or " dissolved " bones. The material should be extracted 

 with water, and the presence of soluble phosphates in the 

 solution shown by testing with ammonium molybdate. 



id) Bone Superphosphate. — The mass of bone ash 

 from {a) (see above) is powdered in a mortar. Sixty 

 grams of the material are treated with 30 c.c. of water, 

 as before, and then with 15 c.c. of strong sulphuric acid. 

 Effervescence, due to the presence of carbonate, will 

 take place, and a dry, friable mass of bone superphos- 

 phate will be left behind. The presence of soluble 

 phosphate in this material is shown by boiling with a 

 little distilled water, filtering, and testing the filtrate 

 with molybdate solution in the usual manner. 



{e) Precipitated Phosphate. — A solution is prepared 

 by treating raw bone or bone meal with hydrochloric 

 acid as in {a). To the filtered solution is added 

 powdered chalk until no further effervescence takes 

 place. The precipitated material is washed once or 

 twice by decantation and then dried on the water-bath, 

 and forms "precipitated phosphate," which is sometimes 

 used as a manure or an adjunct to animal feeding. Its 

 solubility should be tested with ammonium citrate 

 solution and with distilled water. 



Rock Phosphates and Superphosphate. 



The chief mineral phosphates are apatite^ 2Ca3(P04)2 . CaFa, the 

 coprolites^ and the extensive rock-phosphate deposits such as are met 

 with in Belgium, Florida, Algiers, Aruba, and elsewhere. The 

 rock phosphates are largely used as a source of superphosphate of 

 lime, the well-known fertiliser. 



