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and they contain from 30 to 80 per cent, of Ca 3 P 2 O 8 . The 

 Trinchinopoly nodules may be classed as coprolites of a 

 superior kind. 



878. Bones, bone-dust, bone-shavings and ivory-shavings 

 are also very rich in phosphates. They contain from 45 to 

 55 per cent, of phosphates chiefly as tricalcic phosphate, and 

 partly also in the form of magnesium phosphate. Bones 

 containing also 3! to 4^ per cent, of nitrogen, 3 per cent, of 

 CaCO 3 and 4 per cent, of alkaline salts (including silica\ may 

 be regarded in the light of a general manure also. 



879. Boiled bones (whole or dust) are richer in phos- 

 phates (45 to 60 per cent.), calcium carbonate (3 to 9 per cent.) 

 and alkaline salts including silica (4^ to 13 per cent.), but they 

 are poorer in nitrogen (\\ to 3 per cent.). 



880. Animal charcoal is still richer in phosphates (64 to 

 87 per cent.) but poorer in the other substances. Bone-ash 

 contains as much as 77 to 88 per cent, of phosphates and 4 to 

 6 per cent, of calcium carbonate, but it contains no nitrogen. 



88r. The slag of iron foundries is another important 

 source of phosphatic manure, sometimes containing the 

 equivalent of as much as 78 per cent, of Ca 3 P20 8 . 



882. As far as phosphates are concerned, apatite, there- 

 fore, may be considered the richest and the cheapest substance 

 to use. It is much cheaper buying apatite at Rs. 2 or even 

 Rs. 3 per maund than bone-dust at Rs. 2 per maund. In 

 itself however it is not a complete manure, as if contains no 

 nitrogen or potash. With the addition of potassium nitrate 

 or saltpetre, apatite forms a most valuable manure. It 

 should be noted, however, that like bone dust, or coprolite, 

 apatite is also a highly insoluble substance. By the addition 

 of sulphuric acid, bone dust, or powdered apatite and coprolite, 

 maybe converted into super which readily dissolves in the 

 soil, but, on the whole, it is better to use these substances 

 finely powdered, but not converted into super, as a fertiliser 

 of the soij, without expecting any immediate benefit ip 



