MANUFACTURE OF BONE SUPERPHOSPHATE. 193 



to the enormous extension of the use of chemical manures, the value 

 of these ashes has been better appreciated. They are sold to out- 

 ward bound ships, who purchase them as ballast. As they are in 

 the pulverulent state, bones are also mixed with them, as in 

 that way they are less cumbersome. 



The unceasing demand for this excellent waste bv chemical 

 manure factories has diminished the stocks ; on the other hand 

 bones are utilized to better purpose, the result being that bone ash 

 has now almost disappeared from the market. Five samples ol 

 bone ash analysed by Yoelcker had the following composition : — 



TABLE LII.— SHOWING THE COMPOSITION OF FIVE SAMPLES 



BONE ASH. (VOELCKEE.) 



By picking out the big lumps, which consist of almost pure bone 

 ash, a product containing about 85 per cent of phosphate of lime is 

 obtained. The fine powder which contains almost all the sand is, 

 naturally, less rich in phosphate. Bone ash is chiefly used for 

 making precipitated phosphate of lime, according to the method 

 already described. They are worth about £3 per ton. The com- 

 position of bone ash corresponds to the following formula : — 



Ca3(PO,)2 + [Ca3(PO,)oCaOCaHPOJ 



but 2 to 3 per cent of CaO are replaced by MgO, K.^O and Na._,0 and 

 4 to 6 per cent of phosphoric acid by CO.,, CI and F. 



MamifacUtre of Precipitated Phosjjhate of Lime. — Precipitated 

 or basic phosphate of lime is a bye-product of the manufacture of 

 glue. If hydrochloric acid be poured on fat extracted bones, it 



13 



