150 MANTKE3. 



tine is dissolved away, and the earthy matter left 

 in an available condition, from its softness, is a very 

 good way of rendering them useful ; but it requires 

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

 ratus. 



SUPEK-PHOSPHATE OF LIME. 



Super-phosphate of lime is made by treating phos- 

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

 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 represent 

 what in chemistry 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 Ibs. of phosphoric acid combines with three 

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

 Now, by adding to this compound one equivalent 

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

 lent (28 Ibs.) of the lime to be taken away, leaving 

 the 72 Ibs. of phosphoric acid combined with only 

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

 phuric acid (or 80 Ibs.) we cause the removal of 

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

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

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



