Phosphatic Materials used for Agricultural Purposes. 27 



The same bone-ash was likewise submitted by myself and by 

 Mr. Sibson to an analysis, in which the ordinary precipitation 

 method was adopted, and the following results were obtained : 



Water 



Organic matter .. 



Phosphates 



Carbonate oflime 



Alkaline salts 



Insoluble siliceous matter 



103-04 103-39 



In explanation of these results, I may observe that the excess 

 in the analyses is principally due to the circumstance that all the 

 lime which is not united with phosphoric acid is introduced 

 here as carbonate of lime. The alkaline salts likewise help to 

 increase the excess, for in reality the greater part of the alkalies 

 occurs in bones as such, or in union with phosphoric acid, the 

 total amount of which is mentioned in the analyses already. 

 The direct weight of the thoroughly-heated residue, which is 

 obtained on evaporation of the liquid from which the phosphates 

 and the lime have been removed, therefore gives the alkalies 

 too high. 



In reality commercial bone-ash contains seldom more than 

 If to 2 per cent, of carbonate of lime, and the lime which is not 

 in union with phosphoric acid, nor with carbonic acid, must 

 therefore be present in some other state of combination. Some 

 of it, no doubt, is present as fluoride of calcium and some as 

 silicate of lime ; silicate of lime is not a normal constituent of 

 bone, but it is produced when bones are reduced to ash in large 

 heaps. The silica, which is usually attached to raw bones in 

 the shape of fine sand, at a high temperature, decomposes some 

 of the carbonate of lime which bones naturally contain, and gives 

 rise to silicate of lime. 



It might, perhaps, be supposed that bone-ash contained some 

 caustic lime, arising from the high temperature at which the 

 bones are sometimes burned. But this is not generally the case, 

 as I have proved repeatedly by determining the amount of car- 

 bonic acid in the natural sample, as well as after having moistened 

 and heated it with carbonate of ammonia. Had there been any 

 caustic lime present in the bone-ash, the portion treated with 

 carbonate of ammonia would have yielded a larger amount of 

 carbonic acid than the sample analysed in its natural state, 

 whereas both furnished almost identical results. 



Again, commercial bone-ash contains a little sulphate of lime, 

 but its quantity is quite insignificant. 



In all the following analyses, phosphoric acid and lime have 



