19i CHEMICAL MANUEES. 



dissolves the phosphoric acid contained therein. An acid sohition 

 is then obtained of phosphate of Hme, and as a residue the osseous 

 matter, ossein, the gelatine of which is extracted by boiling. For- 

 merly, the acid solution of phosphate of lime was not considered of 

 any value, and to get quit of it, no better outlet could be found for 

 it than to run it into the river. But now the phosphate of lime is 

 recovered by precipitating its solution by caustic lime. Unfortun- 

 ately, the manufacturers are not careful enough in working; the 

 phosphate of lime which they put on the market often contains 12 

 to 15 per cent of carbonate of lime, or of caustic lime, and a 

 large proportion of chloride of lime [? calcium chloride], which 

 renders it less fit for manure manufacture. The analysis of one 

 of these products furnished the following results : — 



TABLE LIII. — ANALYSIS OF PEECIPITATED PHOSPHATE OF LIME. 



of which nitrogen, 2-68 per cent, 

 phosphoric acid, 28 per cent. 



100-00 



Lately the manufacture of phosphate of lime in glue factories has 

 been perceptibly improved, and the product put on the market is of 

 better quality. ' Precipitated phosphates of lime are also made from 

 phosphates unfit for making superphosphates, and from bone ash, but 

 in these cases the impurities contained in the raw material, such as 

 oxide of iron and alumina, are likewise dissolved, and remain in the 

 product.^ 



The manufacture of precipitated phosphate of lime consists, as 

 already mentioned, in decomposing phosphate of lime by hydrochloric 

 acid, and in , separating the chloride of calcium after the equation — 



Ca3(P04)2 + 2HC1 = 2CaHP0, + CaCl, 



The phosphoric acid is precipitated from its solution by milk of 

 lime. The neutralization must be done with care, for it only 



1 The author gives no explanation here of why he should select the purest 

 material, such as bone ash, to make precipitated phosphate, and then go to the 

 opposite extreme to select the most impure, so impure that they cannot be 

 used to make even ordinary superphosphate. The analysis given is certainly not 

 of one made from bone ash. The phosphate of iron content again is too hi<ih 

 to be made from bones even if indicated by the 2-68 per cent, of nitrogen.— Tr. 



