The Composition and Use of Fejittlizees. 233 



Bone-Black, known also as bone charcoal and animal charcoal, 

 is extensively used in refining sugar. After it has been used sev- 

 eral times, portions become useless for refining purposes and 

 are then soid as fertilizer. Bone-black is made by heating bones 

 in closed vessels, the air being excluded. By heating bones in 

 this manner, the fat, water, and nitrogen are removed from the 

 bones; and the bone-black remaining consists mainly of insoluble 

 calcium phosphate and carbon or charcoal. The presence of the 

 carbon hinders the decomposition of the phosphate, so that it is, 

 in this form, not readily available as food for plants. Good 

 bone-black may contain 30 or more per cent, of phosphoric acid. 



Fish. — Phosphoric acid is contained in fish and fish-scrap to 

 the extent of 7 or 8 per cent. In many cases the fish is acidu- 

 lated with sulphuric acid and its phosphoric acid is thus nearly all 

 rendered available. 



Phosphaiic Guanos or Rock-Guanos. — Guanos generally con- 

 sist chiefly of the dung of sea-fowls, though the term is applied 

 to other animal products. They are generally found in beds re- 

 sembling earthy deposits. The guanos which are called phosphatic 

 contain little or no nitrogen. Their phosphoric acid is generally 

 in the form of insoluble phosphate of lime, iron and alumina. 

 These guanos come mainly from certain islands in the Pa- 

 cific ocean, and from Caribbean sea and West India islands. 

 The amount of phosphoric acid in different guanos is very variable, 

 ranging from below 15 to over 30 per cent. 



Rock Phosphates or mineral phosphates are known under sev- 

 eral different names, which generally designate the localities from 

 which they come, as South Carolina Eock, Florida Bock, Tennes- 

 see Bock, West India Bock, etc. Other forms of mineral phos- 

 phates are known under the names of Apatite, Coprolite and 

 Phosphorite, which are found in various places in America and 

 Europe, and some of which are used in making commercial fer- 

 tilizers. However, the greatest source of supply of phosphoric 

 acid is the phosphate rock of our Southern States. The rock- 

 phosphates are extensively used in making superphosphates. 

 When ground to a very fine flour-like powder, rock-phosphates 

 are called " floats." Bock-phosphates contain usually from 20 

 to 30 per cent, of phosphoric acid, and some as much as 35 or 

 40 per cent. 



Superphosphates are known under several different names, 

 such as acid phosphate, dissolved bone, dissolved rock, dissolved 

 bone-black, etc. Superphosphates are formed by treating some 

 form of insoluble phosphate of lime, as rock-phosphate, bone, 



