150 M.VXLRRS. 



tine is dissolved away, and the eartlij' matter left 

 in an availa]>le condition, from its softness, is a very 

 ^ood way of rendering them nseful ; but it requires 

 the use of a steam boiler, and other expensive appa- 

 ratus. 



SCPER-PnOSPnATE OF LIME. 



Sxiper-phosphate of Ihne, is made by treating phos- 

 phate of lime, or the ashes of bones, with sulphuric 

 acid. 



Phosphate of lime, as it exists in bones, consists 

 of one equivalent of phosphoric acid and three equi- 

 valents of lime. 



The word " equivalent " is here used to repi-esent 

 what in cheinistry is known as the combining pro- 

 portion of each element of a compound body — that 

 is, one pound of one substance combines with one 

 and one-half pounds of another, and these propor- 

 tions are invariable. 



In bone earth, or phosphate of lime, one equiva- 

 lent, or 72 lbs. of phosphoric acid combines with three 

 equivalents (of 28 lbs. each), or 84 lbs. of lime. 

 Xow, by adding to this compound one equivalent 

 (or 40 lbs.) of sulphuric acid, we cause one equiva- 

 lent (28 lbs.) of tlie lime to be taken away, leaving 

 the 72 lbs. of phosphoric acid combined with only 

 56 lbs. of lime. By using two equivalents of sul- 

 phuric acid (or SO lbs.) we cause the removal ot 

 56 lbs. of lime, leaving only 28 lbs. combined with 

 the 72 lbs. of phosphoric acid. This is super-phos- 

 phate of lime, which is readily soluble in water. It 



