AGRICULTURE. 



[CH. 



The carbonic acid of the atmosphere carried into the 

 soil in the rain-water, and any which might have been 

 produced in the soil, helped to make the bone more 

 rapidly soluble. The following diagram shows the 

 action of the carbonic acid upon the tri-calcic phos- 

 phate in bone 



67. Up to 1840 phosphate of lime was added to the 

 soil by the use of bones, having varying degrees of 

 fineness ; but, in that year, Liebig proposed a chem- 

 ical treatment of bones, whereby they were 

 rendered more rapidly soluble, and consequently were 

 ready for use for the crop with less loss of time. In 

 fact, instead of the farmer having to wait some months 

 for any general action of the bone, this chemical 

 treatment made the bone ready for immediate use. 

 Liebig's discovery of the means whereby these results 

 could be attained with such promptitude, was like 

 many other great discoveries exceedingly simple. He 

 imitated the natural decomposition of bone as it takes 

 place in the soil, but he accomplished the work more 

 quickly by using a stronger acid. We have seen (66) 

 that the carbonic acid slowly and quietly took from 

 the tri-calcic phosphate some of its lime, and thus in- 

 creased the solubility of the bone, but Liebig used 

 sulphuric acid, which is a very powerful acid, and this 

 accomplished in one hour more than the carbonic acid 

 could do in one year. The chemical change was 

 practically completed at once, and the phosphate of 

 lime in the bone became immediately soluble in 

 water. 



