156 



PROCEEDINGS OF THE CHEMICAL DEPARTMENT. 



By Thomas Anderson, M.D., F.K.S.E, Chemist to the Society. 



I.— FIELD EXPERIMENTS ON THE ACTION OF URIC ACID 

 AND GELATINE AS MANURES. 



In the 11th volume of the Transactions of the Society, I pub- 

 lished the results of a series of experiments on the action of 

 uric acid as a manure, undertaken for the purpose of solving a 

 doubt which had been expressed as to whether that substance is 

 capable of affording a supply of nitrogen to the crop to which it 

 is applied. The practical importance of determining this point 

 lies in the fact that more than half the nitrogen in Peru- 

 vian guano is present in the form of uric acid ; and if that sub- 

 stance cannot yield up its nitrogen to the plant, it is manifest 

 that however good may have been the effect of that manure, the 

 fanner who goes on the assumption that all its nitrogen is 

 equally available as food for his crops, must have attached to it 

 a greater value in proportion to other manures than it really 

 merits. 



It may be considered as a matter established beyond all 

 doubt that complex nitrogenous compounds, such as those which 

 form part of the tissues of plants and animals, are incapable of 

 direct absorption into the vegetable system, but must first un-, 

 dergo decomposition, and yield up their nitrogen in the form 

 either of ammonia or nitric acid before it can be assimilated ; 

 and it is very clear that however rich a substance may be in 

 that element, it must be valueless in an agricultural point of 

 view, unless it is capable of undergoing this change. It had 

 been always assumed that uric acid was readily decomposed in 

 the soil until Liebig recently called this opinion in question, and 

 excluded its nitrogen from among the valuable constituents of 

 Peruvian guano. I had myself always held an opposite opinion, 

 and maintained that the nitrogen, not only of uric acid, but of 

 all other nitrogenous compounds existing in manures, might be 

 calculated as ammonia without entailing any practical error, and 

 this certainly seems to be the fair and legitimate inference to 

 be drawn from the observed results of the action of manures. 

 But as a different opinion had been expressed, it appeared most 

 desirable that both views should be submitted to the test of 

 actual experiment, and I was thus induced to undertake the 

 investigation which has been referred to at the outset. The 

 results of these experiments, for the details of which I must 

 refer to the paper itself, proved incontesibly that uric acid did 



