Composition and Value of Guano. 



219 



various sources. Leaving, however, the further development of 

 this point for the present, we shall proceed to examine the existing 

 sources of a supply of ammonia for agricultural use. 



The different salts of ammonia, as the bicarbonate (the common 

 smelling salts), the muriate (known as sal ammoniac), and the 

 sulphate, are all to a considerable extent articles of commerce, 

 being in one way or another employed in the arts or in medicine. 

 The first of these, however, is not at present sufficiently cheap to 

 be profitably employed in practical agriculture. 



Many years ago the sources of ammonia were extremely limited, 

 and its salts were correspondingly dear ; but, by the general in- 

 troduction of gas, an abundant quantity of this alkali has been 

 opened out. It is very commonly known that, amongst the other 

 products of the distillation of coal in the ordinary process of pre- 

 paring gas, a large quantity of an ammoniacal liquor is obtained, 

 and many who read this paper may have made use of it as a 

 manure under the name of f< gas-liquor." The origin of this liquid 

 is very simple. In all samples of coal which have been examined 

 with a view to detect it, nitrogen has been found in variable pro- 

 portion, derived evidently from the plants from which the coal has 

 been formed. When the coal is heated the nitrogen is converted 

 into ammonia, which collects in the " condensers" principally as 

 carbonate or hydrosulphate. By the addition of mineral acids 

 and subsequent evaporation any desired salt of ammonia can be 

 produced. 



The sulphuric is of all other acids that which is most valuable 

 in the arts, and, as its very numerous applications have led to 

 great perfection in the manufacture of this acid, it is under most 

 circumstances the only compound of its class which is economically- 

 applicable. Accordingly, large quantities of sulphuric acid have 

 been used in the preparation of sulphate of ammonia from the 

 ammoniacal liquor of the gas-works. 



Muriatic acid is a refuse product in the preparation of carbonate 

 of soda, and under some circumstances it is employed in the pre- 

 paration of an ammoniacal salt from gas-liquor with more eco- 

 nomy than the sulphuric. 



Sulphate of ammonia costs from 117. to 12/. per ton, and no 

 inconsiderable quantity has been sold as manure at this latter 

 price. The muriate varies in price between 171. and 21/. per 

 ton. Whether these salts can, with a profit to the manufacturer, 

 at present be prepared at a lower price, I cannot say ; but as, by 

 that mutual dependence of the arts of life which meets us at 

 every turn, the gas-works of England are destined some day, and 

 probably before long, to become auxiliary to the production of 

 food by supplying the farmer abundantly and cheaply with am- 



