24 AMMONIA FIXEKS. 



tact with carbonate of ammonia has been proved to 

 effect the conversion of the ammonia into sulphate of 

 ammonia. It is also believed to retard the decompo- 

 sition of the manure. 1 Copperas, or ferrous sulphate, 

 while a soluble salt, and while thus acting in a more 

 speedy manner in fixing the ammonia, is not so well 

 suited, owing to the hurtful influence it is well known 

 to possess on plant-life. It is only right to remember 

 that there may be circumstances in which copperas 

 may, in small quantities, act, even beneficially, as 

 a manure, as Griffiths' experiments would seem to 

 indicate. The above objection, however, cannot be 

 urged against sulphate of magnesia. In addition to 

 fixing the ammonia, sulphate of magnesia may very 

 probably fix the soluble phosphoric acid. Kainit, 

 which consists of a mixture of sulphates and chlor- 

 ides of potassium and magnesium, has also been sug- 

 gested for this purpose. By using such a fixer, the 

 value of the resulting manure would be much en- 

 hanced. In conclusion, it must be remembered that 

 all the above-named fixers act very much in the same 

 way viz., by converting the volatile carbonate of 

 ammonia into sulphate of ammonia. 2 



2. Cow-manure. The composition of the manure 

 formed from the excrementitious matter of the cow is 

 very much less constant than is the case in the horse- 



1 Schulze recommends one-third of a pound per day of sulphate of 

 lime for each horse. 



2 See Appendix, Note X., p. 58. 



