130 GYPSUM DECOMPOSED IN MANURE HEAPS. 



with advantage : there is one point, however, to which I would 

 draw the attention of the scientific agriculturist. 



Gypsum, in the presence of water and organic matter, is very 

 readily deprived of its oxygen, and converted into sulphuret of 

 calcium. In the baths of Louesch, the warm waters (80 to 90 

 F.) are sulphureous, though, as they issue from the spring, they 

 contain only sulphates, and chiefly gypsum.* The contact of 

 the skins and perspiration of the patients who bathe in it, and 

 live in it, I may say, six or eight hours a-day, produces this 

 change. In manure-heaps, in which gypsum is covered up, a 

 similar change must take place, and one or more of several 

 effects will follow. 



First, The carbonic acid produced in the fermenting mass 

 will decompose this sulphuret, forming carbonate of lime, and 

 evolving sulphuretted hydrogen, thus increasing rather than 

 diminishing the smell. Or second. The carbonate of ammonia 

 given off in the heating mass will decompose the sulphuret of 

 calcium, forming carbonate of lime and hydro-sulphuret of 

 ammonia. This latter has a smell, and is by no means fixed, 

 supposing its existence to be permanent. But the carbonic 

 acid produced will decompose it also, and form carbonate of 

 ammonia, again evolving sulphuretted hydrogen. Or thirdly, 

 The sulphuret of calcium will expend its sulphur so far, in 

 combining with all the iron which the manure may contain, 

 giving it a blacker colour and more decomposed appearance, 

 but not fixing its ammonia. 



While therefore it is true that, when strewed on the surface 

 of moist fermenting heaps, gypsum in fine powder may arrest 

 and fix the ammonia which is escaping, it is deserving of 

 inquiry how far it serves any good purpose, other than that of 

 adding lime to it, when it is actually mixed with the fermenting 

 manure. If there be anything in this reasoning, it may account 

 for different opinions and results, and is, I think, not unworthy 

 of being experimentally tested by some one who has the requi- 

 site chemical knowledge, and has the means of devoting to the 

 experiments the requisite time and attention. 



* FONTAN. An. de Chem. et de Phys., (1840,) xxiv., p. 280. 



