20 Chemical Composition and Commercial Value of 



of lime and likewise more alkaline salts than others. We must 

 not, therefore, expect to find always in the richest samples the 

 highest percentage of carbonate of lime, &c., nor in those poor in 

 bone-earth necessarily a correspondingly low percentage of the 

 last-mentioned constituents. But, generally speaking, a higher 

 percentage of carbonate of lime and alkaline salts will be found 

 in good samples of bone-ash than in those* that are inferior. 

 This we may naturally expect, for as pure bones contain a cer- 

 tain amount of carbonate of lime, &c., the less sand a sample of 

 bone-ash contains, and the more perfectly the bones are burned, 

 the more phosphate of lime and likewise the more of all the 

 other incombustible constituents it necessarily must contain. 

 On the other hand, if bones are imperfectly burned and con- 

 taminated with much sand, they naturally must yield an ash 

 which is not only poorer in phosphates but in all the ash- 

 constituents of bones. At all events, bone-ash must contain 

 more bone-earth and more carbonate of lime and other mineral 

 matters than the bones which furnished the ashes. 



In commercial analyses, however, the proportions of carbonate 

 of lime, &c., are frequently stated to be far smaller than can be 

 the case. This mistake arises from the faulty determination of 

 the bone-earth. When determined in the usual way, the precipi- 

 tated bone-earth invariably contains a good deal of carbonate of 

 lime. The phosphates are therefore given higher than they are 

 in reality, and, as it is usual to determine the rest of the lime 

 which is not united with phosphoric acid and the alkaline salts 

 together by difference, the latter constituents are consequently 

 stated too low. 



Thus an analysis lately brought under my notice gives the 

 composition of a sample of bone-ash as follows : 



Charcoal 2-1 



Sand 4-3 



Water 3;8 



Carbonate of lime 1'9 



Phosphate of lime .. .. 87*9 



100-0 



Another chemist, who analysed the same bone-ash, gives the 

 following results : 



Moisture 3'00 



Carbonaceous matter 3'00 



Siliceous matter 3*90 



Phosphate of lime 84-84 



Carbonate of lime (4-48) &c 5'26 



100-00 



Tn both analyses the amount of phosphate of lime is given too 

 high, and that of carbonate of lime and alkaline salts too low. 



