PHOSPHO-NITBOGKENOTJS MANUEES 241 



Bones are also subjected to a process of destructive 

 distillation for the purpose of making bone char, which 

 is largely used in sugar refineries. In this process the 

 whole of the nitrogen is volatilised, but the phosphate 

 remains. The bone char is therefore fairly rich in 

 phosphates, and in the spent condition is sometimes used 

 as manure, but more frequently it is burned to bone ash. 



Finely powdered bones moistened with water and piled 

 up in heaps readily undergo fermentation, and the nitro- 

 genous matter is thus rendered more readily available. 

 The product is sometimes dealt in commercially under 

 the name of fermented bones. It has much the same 

 composition and properties as ordinary bone meal. 



By far the most effective way of hastening the action 

 of bones is to treat them with sulphuric acid. The 

 product is called dissolved or vitriolated bones, and is 

 of quite a different character from any of the bone pro- 

 ducts previously mentioned. 



Crushed Bones. Ground or crushed bones are pre- 

 pared from samples which have been altered by cooking, 

 exposure, etc., or from fresh bones after removal of the 

 fat. They are sometimes known as " raw bones " to 

 distinguish them from those which have been vitriolated, 

 or from which a considerable proportion of the nitro- 

 genous matter has been removed by steaming. 



The composition, is of course, variable, but in general, 

 they contain from 45 to 55 per cent, of tricalcic phos- 

 phate, and from 3 to 4 per cent, of nitrogen. Both 

 constituents are insoluble in water, and the action of 

 bones is therefore slow. In light open soils, if not too 

 dry, they are much more rapidly oxidised than in those 

 of closer texture. 



The activity of bones, like that of other manures, 

 depends to a large extent upon the size of the pieces, 

 and they are now generally used in the form of fairly 



S.M. B 



