SUPERPHOSPHATE OF LIME 259 



The amount of oil of vitriol used above is by far too great. 

 It has been calculated thus, to show that no amount of O. V. 

 added to the mixture above, will produce free phosphoric 

 acid. That may be obtained by adding O. V. to the clear 

 liquor^ which may be drawn from the mixture by leaching. 

 Still an excess of oil of vitriol has its value, as will be here- 

 after shown. If the proportion is reduced for 100 lbs. pure 

 bone earth, to 87|, or | the weight of the bone earth, it will 

 be seen, presently, that this will be an advisable proportion 

 to be used, whatever "form of bone earth may be used for 

 conversion into superphosphate of lime. 



So much for the chemistry of this subject. Before this 

 knowledge can be practically applied, the composition of 

 bone must be recollected. As has been shown (302), bone 

 comprises other substances of mineral origin, besides bone 

 earth. These also will combine with O. V., and if it is in- 

 tended that the 88 parts of bone earth in 100 parts of bone 

 ash shall all be converted into superphosphate, these hungry 

 mouths must be first satisfied, or else they will surely help 

 themselves before the phosphate, their better, is served. 



On referring to the composition of raw bones (302), it is 

 seen that 200 lbs. will afford 100 lbs. of bone ash, composed 

 as follows : 



Phosphate of lime, 88 lbs., requiring 77 lbs. of oil of vitriol. 

 Carbonate of lime, 6 " " 6 " " " 



Magnesia, . . 1.25 " 1.49 " " 



Soda, . . . 3.25 " 3. « " " 



Alkaline sulphates, 



and chlorides, . 1.50 " " '* " " 



100 lbs. 87.49 



Bone meal from 



raw bones, . 100 lbs., require 43.75 " ** 



