214 



On Superphospliate of Lime. 



to add to any of the phosphoric substances which will come before 

 MS, and we now proceed to their description. 



Bones — in the natural state — that is to saj raw " or unboiled 

 — contain a certain quantity of moisture and fat, a large pro- 

 portion of cartilage or gelatine and of phosphate of lime, with a 

 smaller quantity of carbonate of the same base : small portions 

 of magnesia and alkaline chlorides and sulphates are also found 

 in bones, but in reference to our purpose they are wholly unim- 

 portant. The quantity of water, fat, and gelatine in bones varies 

 in every different animals and in the same animals of different 

 ages, so that it is impossible to give any analysis of them that 

 shall apply to all cases. Our chief concern is with the phosphates 

 and carbonates of lime, the quantity of which may be judged of 

 with sufficient accuracy. 



The following num.bers v/illy I think, pretty well represent the 

 composition of raw bones : — • 



Water, fat, and cartilage or gelatine . . . .48 



Phosphate of lime, with small quantities of phosphate 

 of magnesia ........ 46 



Carbonate of lime ....... 4 



Alkaline chlorides and sulphates, &c. . ... 2 



100 



Of the first item we may allow perhaps 12 parts for water and 

 8 parts for fat, leaving the proportion of gelatine at 28 per cent.* 



It is important that attention should now be called to the effect 

 which carbonate of lime must have upon our calculations, when- 

 ever it occurs in company with the phosphate. The first action of 

 the acid is upon the carbonate, the lime of which must be neu- 

 tralized by sulphuric acid before the phosphate can be attacked; 

 and in using those phosphoric materials which contain much car- 

 bonate of lime, such as the Suffolk coprolites, a great deal of 

 waste must necessarily occur from this cause ; and for the same 

 reason the product will contain considerably more sulphate of 

 lime than is accounted for by the action of the acid on the phos- 

 phate. 



Every 100 parts of carbonate of lime require 80 parts of 

 real sulphuric acid to convert them into sulphate of lime, and 

 this quantity is contained in 98 parts of oil of vitriol and 124 

 parts of brown acid (sp. gr. I ZO). The carbonic acid is driven 

 off in the process ; and as this constitutes 44 parts of 100 of car- 

 bonate of lime, 56 of lime unite with the SO parts of real acid to 

 produce 136 parts of the sulphate : but sulphate of lime unites 



* In a former paper I estimated the proportion of gelatine in raw bones at 33 per 

 cent., and the nitrogen consequently supplied by them at 6 per cent. I have reason 

 to think that this estimate was too high for raw bones, though it would apply with 

 tolerable correctness to bones deprived of their water and fat. 



