392 



Nitrate of Soda as a substitute for Guano. 



pastures in summer give rise to the formation of nitrates. The walls of stabler 

 and cowhouses, which by absorption have been moistened with urine, often 

 give on their surfaces efflorescences of niire. 



The conversion into nitric acid of the nitrogen of solid animal or vegetable 

 matters constantly occurs when these bodies are in contact with earthy calca- 

 reous mattei-s. Even in the absence of calcareous substances nitric acid is 

 formed in such common dung-heaps as consist merely of decomposing animal 

 and vegetable macter ; for one part of the ammonia produced by ordinary 

 decomposition acts as the alkaline base to another portion, which by oxidation 

 is converted into nitric acid. Xitrate of ammonia may always be found in 

 dung-heaps. Xitrates are also present in all shallow wells adjacent to church- 

 yards, and in those which derive their liquid supplies from strata into which, 

 cesspools empty themselves. 



The proper conditions for the formation of nitrates are always to be found 

 in well-drained and well-manured fields, particularly when they contain cal- 

 careous matter. One of the grreat uses of liming is to furnish the alkaline 

 matter where it is deficient. In our laboratories we have examined a great 

 number of soils, and in almost every instance have detected the presence of 

 nitre. 



In my opinion, a proper knowledge of the mode of forming nitre beds would 

 be of considerable importance ro the farmer ; for by their use not only would 

 he be able to conserve the ammonia of his manure when he had more of the 

 latter than he could at once apply to the land, but by using the liquid manure- 

 from the tanks the necessary moisture would be given to the heap ; and whilst 

 the aqueous particles, so expensive to carry, would gradually evaporate, the 

 valuable matters of the liquid would be retained in the compost. 



The mode of making artificial nitre-beds has been shortly described in my 

 lecture to which you refer. It is exceedingly simple. A layer of calcareous- 

 matter forms the base of the heap, and layers of horse-dung, cow-dung, carrioUj 

 or other similar matters, alternating with layers of marl, mortar, or spent lime, 

 will constitute the nitre-bed. The mixture should always be kept moist with 

 urine, or urine and water : but too much water, as from rain, would be injuri- 

 ous, and the heap ought therefore to be kept under cover. The compost should 

 lie as loosely as possible together, that the air may be easily able to permeate 

 the mass. The heap should be thoroughly incorporated, and lightly turned 

 over once in two or three months. In from six to nine months it will be ready 

 for the farmer's use. Quick li/jie ought not to be used in making nitre beds, as 

 its first and most powerful action is lo drive otf the ammonia from the mianure. 



It must be understood that, by making mixtures calculated to give rise to^ 

 the artificial production of nitrates, we have a means of preventing the loss of 

 ammonia which takes place in a common dung-heap ; and that, under ordinary 

 circumstances, manures containing either nitrates or ammonia, without any 

 important amount of other substances, are valuable exactly in proportion to th& 

 amount of nitrogen they contain. It may be necessary to mention that in 

 soils and dung-heaps the nitric acid produced by oxidation of ammonia is re- 

 concerted into ammonia when putrefaction is taking place and access of air is 

 prevented. 



In conclusion, I may mention that I have analysed a portion of a large nitre- 

 bed of about 40 tons, which was (about ten months since) made on the pre- 

 mises attached to the College at Kennington. Though the heap has been 

 exposed to all the rains of the season, it was found that 1 pound weight of the 

 compost contained 21 grains of nitric acid, which is equivalent to 34 grains of 

 saltpetre. This is an amount much below what we should have found had 

 we had the heap under cover. 



I am, my dear Sir, yours very truly, 



College of Agriculture and Chemistry, J. C. Xesbit. 



Kennington, Dec. 13, 1853, 



