No. 6. DEPARTMENT OF AGRICULTURE. 837 



This product, also known as bone black and animal cLarcoal, is 

 used extensively in sugar refineries for taking the coloring matter 

 out of raw sugars. From time to time portions of the bone char- 

 coal cease to be ellective in clarifying and the spent black is then 

 sold by the refineries for fertilizing purposes. All the phosphoric 

 acid originally in the bones is retained, but the presence of carbon 

 prevents the phosphate from decomposing. It is as "dissolved bone 

 black" that this article is generally found on the market. Dissolved 

 bone black contains a large proportion of soluble phosphoric acid 

 and a very small amount in the insoluble form. 



BONE ASH. 



The supply of bone ash comes mainly from South Africa, where 

 the bones of animals are used as fuel in extracting the fats from 

 the carcass. In the process of burning, all the organic matter is de- 

 stroyed, so that the nitrogen of the bones is lost. Bone ash contains 

 from 30 to 35 per cent, phosphoric acid, and in a form so insoluble 

 that this material is little used as a fertilizer until it has been treated 

 with acid. 



At one time this source supplied considerable phosphoric acid and 

 was found on all markets, but at the present time little or none is 

 to be found. 



PRECIPITATED BONE OR PRECIPITATED PHOSPHATE. 



Every year large quantities of bones are treated with hydrochloric 

 (muriatic) acid for the purpose of dissolving the mineral matters 

 of the bone and of obtaining their ossein for use in the manufacture 

 of gelatine. To the clear solution of phosphate of lime in hydro- 

 chloric acid thus obtained is added enough milk of lime to neutralize 

 the acid and precipitate the phosphate. The precipitate is in the 

 form of a very fine powder and may, be used directly for fertilizing 

 purposes, or it is sometimes treated with sulphuric acid to render 

 the phosphates soluble as, precipitated, this material contains, on 

 the average, about 18 or 19 per cent, of phosphoric acid. 



There is also some precipitated phosphates that come from other 

 manufacturing sources. 



BONE TANKAGE. 



Tankage is the residue remaining in the tanks used for boiling 

 cattle heads, feet and all sorts of slaughter house refuse. 



Bone tankage represents an important source of phosphoric acid. 

 It is so closely related to raw bone or steamed bone as far as its con- 

 tents of phosphoric acid are concerned that it is not necessary to 

 say more here on that point. Tankage is also quite available as a 

 source of nitrogen or ammonia in making mixed fertilizers. There 



