BONES. 255 



frost is out an inch or two, or if used for root or grain crops, 

 harrowed or lightly ploughed in. 



Thirdly. Bone, deprived of all its animal matter, calcined 

 or burned bone, hone ash, sugar house refuse, or bone black. 

 Bones are easily reduced to the state of ash by piling them 

 up with a little light wood or fagots, and firing the mass. 

 The bones continue burning till reduced to whiteness, be- 

 coming brittle as pipe stems and very easy to grind. By 

 this mode, all animal matter is burned up. If bones are 

 heated in closed vessels, leaving a small vent, as in baking, 

 bone black is produced, containing all the earthy part of the 

 bone, mixed with the coal of the animal portion. This serves 

 for decoloring sugar and other syrups, and after having 

 served this purpose several times, by repeated burning, the 

 spent bone black is sold to farmers and others as sugar house 

 refuse ; when mixed with the scum and other impurities 

 arising during the clarification of sugar, it is more valuable 

 for agriculture than simple sugar house black. 



303. In the state of bone ash, phosphate of lime is more 

 insoluble than as bone meal. It has been found, that by 

 treating bone ash, as also bone meal, with certain acids, the 

 phosphate of lime is brought into a highly soluble state. 

 The cheapest acid, and that commonly used for this purpose, 

 is oil of vitriol, which produces, by its action on bone, both 

 plaster and soluble phosphate of lime, called superphos- 

 phate. 



In this acid state, bone acts quicker, goes farther and lasts 

 longer than in any other form. Acid may, therefore, be 

 economically applied to all forms of bone, entire, partially, 

 or wholly deprived of its gelatine. 



This application is often called dissolving bone in acid. 

 There is no clear solution. It is a mere breaking up, it is a 

 softening, pap-forming process, and bone, in this state, would 



