AMMONIA FIXERS. 23 



The preservatives used to prevent this volatilisation 

 are technically known as " fixers." This they do by 

 chemically combining with the volatile ammonia and 

 forming non-volatile compounds with it. 



Of the acid fixers, hydrochloric and sulphuric acids 

 have been recommended. The former, however, is not 

 well suited for this purpose. It is a strongly fuming 

 acid, and when brought into contact with ammonia 

 forms dense white fumes. The use of sulphuric acid 

 is not open to this objection. Sulphate of ammonia, 

 the salt formed in this case, is one of the most 

 stable (or least volatile) of the compounds of am- 

 monia. If used, it should be largely diluted with 

 water, and the whole mixed with sand. Such a mix- 

 ture, when sprinkled over the stable-floor in even very 

 small quantities, has been found to effectually prevent 

 any loss of the volatile carbonate of ammonia. 



It is not, however, on the whole advisable to use an 

 acid substance as a fixer, since such a substance may 

 act deleteriously on the horses' hoofs. 



Such substances as gypsum, copperas, and sulphate 

 of magnesia, while equally efficient, are not open to 

 this objection. The above-mentioned substances owe 

 their efficacy to the fact that they are compounds of 

 sulphuric acid, which, by combining with the volatile 

 ammonia and forming sulphate of ammonia, prevents 

 its escape. 



Gypsum, or sulphate of lime, although, comparatively 

 speaking, an insoluble substance, when brought in con- 



