380 SOILS 



Boiled and Steamed Bone. Most of the bone used 

 as fertiliser has been boiled or steamed to free it 

 from fat. The fat is objectionable in a fertiliser 

 and is valuable for soap; the meat contains nitro- 

 gen and is used in making glue. Boiling or 

 steaming reduces the amount of nitrogen in the 

 bone, so that it contains about 28 to 30 per cent, 

 phosphoric acid and only about 1 per cent, of 

 nitrogen. About 6 to 9 per cent, of the phosphoric 

 acid is soluble. Boiled or steamed bone, however, 

 can be pulverised much finer than raw bone and 

 this greatly increases its value for immediate use. 

 It is much used in mixed fertilisers and is especially 

 valuable for meadows. 



Both raw and boiled or steamed bone are sold 

 under various trade names, as "meal," "dust," and 

 "fine ground bone." These terms refer to fine- 

 ness, not to composition, and there is no uniformity; 

 the "bone meal ' of one manufacturer may be as 

 fine as the "bone dust" of another. The finer 

 it is, the better, since it decays more quickly. 



Dissolved Boneblack. Raw bones are burnt 

 until they become "animal charcoal" and are 

 readily crushed into a fine powder. This "bone 

 black ' is used in refining sugar. It is then turned 

 over to the fertiliser dealer, who finds that it con- 

 tains 32 to 36 per cent, of phosphoric acid, mostly 

 insoluble, and a small amount of nitrogen. Bone- 

 black is sometimes used directly as a fertiliser, but 

 more commonly is treated with oil of vitriol to make 

 the phosphoric acid in it more soluble. The re- 

 sulting product is "dissolved boneblack" which 

 contains 15 to 17 per cent, of soluble phosphoric 

 acid and is one of the most important of the phos- 

 phates. Some superphosphates are dissolved 

 boneblack. 



