64 Fertilizers 



or fineness of division, and do not refer especially to 

 composition. These names should not be taken as 

 indicating the fineness without personal examination, 

 since frequently the products do not, in this respect, 

 correspond to the name. 



Boiled and steamed bone. 



The larger portion of the bone used as manure has 

 been boiled or steamed for the purpose of freeing it from 

 fat and nitrogenous matter, both of which are products 

 valuable for other purposes. The fat is, of course, of 

 no value as a manure, and its absence is an advantage. 

 The nitrogen, while useful as a manure, is extracted 

 chiefly for the purpose of making glue and gelatine. 



By boiling or steaming, the bone suffers a loss of its 

 original constituents, the chief result of which is to change 

 the proportions of the nitrogen and phosphoric acid con- 

 tained in it. Steamed or boiled bone contains more 

 phosphoric acid and less nitrogen than raw bone, and 

 is also more variable in composition, the relative per- 

 centage of these constituents depending upon the degree 

 of steaming or boiling to which the bone has been sub- 

 jected. 



Bone that has been used for the purpose of making 

 glue, where the chief object is to extract the nitrogenous 

 matter, contains from 28 to 30 per cent of phosphoric 

 acid and from 1J to If per cent of nitrogen. The steam- 

 ing of bone, particularly when conducted at high pressure, 

 also exerts a favorable effect upon the physical and 

 mechanical character of the bone. It destroys its original 

 structure, makes it soft and crumbly, and often reduces 

 it to a finer state of division than can be readily accom- 

 plished by grinding; and, since it is also free from fat, 



