188 FUNCTIONS OF AMMONIA 



and, from its price, can never be employed in practical agricul- 

 ture. It will be interesting, however, to ascertain the nature 

 of its influence upon growing plants. 



8. Humate of ammonia is formed by digesting caustic am- 

 monia or carbonate of ammonia on rich vegetable mould, or on 

 dried and powdered peat. The ammonia causes the decaying 

 vegetable matter to swell very much, and forms a dark brown 

 solution of humate of ammonia. The composition of this humate 

 is not accurately known. It is deserving of being made the 

 subject of field experiment, however, because of the great pro- 

 bability which exists that one of the functions of ammonia in 

 the soil is to form such soluble combinations with the organic 

 matter contained in the soil, and thus to make it capable of 

 entering into the roots of plants. 



All the salts of ammonia are readily soluble in water, and 

 they all give off ammonia when mixed with quicklime or slaked 

 lime, or with caustic potash, soda, or magnesia ; more slowly 

 when mixed with the carbonate of potash, (pearl ash or wood 

 ashes,) or with the carbonate of soda, (common soda of the shops, 

 or soda ash,) and still more slowly when mixed with carbonate 

 of lime, (mild lime or chalk,) or with carbonate of magnesia. 



2. Functions performed by the salts of ammonia in the soil 

 and in the plant. 



1. Functions in the soil. The chemical functions performed 

 by ammonia in the soil will vary with the state of chemical 

 combination in which it is used. 



a Caustic ammonia and carbonate of ammonia will neutralise 

 acid substances, if any such exist in the soil will decompose 

 earthy and metallic sulphates and chlorides, forming sulphate of 

 ammonia and sal-ammoniac will combine with and render 

 soluble the humic, ulmic, and other organic acids, which will 

 thus be rendered available to the nourishment of plants, and, in 

 the presence of lime or alkaline carbonates, will be slowly con- 

 verted into nitric acid. 



b Sal-ammoniac, in the presence of the carbonates of lime or 

 magnesia, will be partially or completely decomposed, forming 

 chloride of calcium or magnesium, and carbonate of ammonia. 



