256 SUPERPHOSPHATE OF LIME. 



more appropriately be called bone-pap. The bone is merely 

 so far reduced that, when rubbed between the thumb and 

 finger, no grit is felt. Bone cannot all dissolve, for the oil 

 of vitriol, when added rightly, miites with the lime of car- 

 bonate and phosphate, and forms with that insoluble sulphate 

 of lime, or plaster. It is this which gives the grayish white 

 look to the bone porridge. 



304. That this subject may be placed in a clear light to 

 him who intends to prepare superphosphate for his own use, 

 or for market, the properties of phosphoric acid must be 

 adverted to. It is, like the acids found in geine, many 

 based, requiring at least 3 portions of base to 1 of acid, for 

 neutralization. These combinations should be well under- 

 stood, and they may be illustrated by reference to the phos- 

 phates of lime ; for 



Phosphoric acid 1 part, lime 1 part, form superphosphate ; acid. 



Do. 1 part, lime, lime, 2 parts, form subphosphate ; less acid. 

 Do. 1 part, lime, lime, lime, 3 parts, form neutral phosphate. 



In this last form it is found in bones ; this forms pure 

 bone earth. If to this neutral phosphate oil of vitriol is 

 added, it combines wuth and removes a portion of the lime 

 from the phosphoric acid, more or less according to the 

 quantity added. No quantity will take away all the lime. 



Each part of lime requires its equivalent of oil of vitriol. 

 If to neutral phosphate of lime, oil of vitriol (which maybe 

 designated by 0. V.) sufficient to unite with one part of lime, 

 is added, the result may be illustrated as follows : 



Neutral phosphate of lime contains one proportion of acid 

 and three of lime, or 



Phosphoric acid, lime, lime, lime, 

 Add, . . . O.V. 



