V.] 



SUPER-PHOSPHATE OF LIME. 



68. But Liebig's process did something more than 

 gain time he obtained the tri-calcic phosphate of the 

 bone in a thoroughly soluble condition, and in this 

 respect the chemical change he accomplished 

 went beyond that which naturally occurred 

 in the soil. The difference will be more clearly under- 

 stood by reference to the following diagram : 



69. If you compare this diagram with that immed- 

 iately preceding it, you will see that a different form 

 of phosphate of lime is obtained from that 

 which had been produced in the soil by the slow 

 decomposition of the bone. In the former case 

 a bi-calcic phosphate was produced, and this is a 

 slowly soluble phosphate of lime. In the latter 

 case we have mono-calcic phosphate produced, and 

 this is rapidly soluble in water. 



70. The treatment of bone by means of sulphuric 

 acid thus introduced by Liebig therefore produced 

 a new kind of manure which has been distinguished 

 as super-phosphate of lime. You will readily 

 understand that it was called super-phosphate d 

 lime, because the phosphoric acid which had been 

 combined with three equivalents of lime had been 

 concentrated upon one equivalent of lime, and the 

 lime was thus super-phosphated, or, in other 

 words, the lime was over- charged with phosphoric 

 acid. It must be remembered that not only is mono- 

 calcic phosphate thus formed, but a large quantity of 

 sulphate of lime is also produced by the action of the 

 sulphuric acid on the bone, and consequently the 



