Gypsum and Lime 349 



due almost entirely to the escape of nitrogen gas, which 

 gypsum is incapable of holding back. 



Everything considered, therefore, it would scarcely 

 be advisable to recommend the purchase and use of 

 gypsum as a conserver of nitrogen. The value of the 

 nitrogen saved would usually be smaller than the value 

 of the material employed. Occasions may arise, of course, 

 when the use of gypsum will prove profitable, as, for 

 instance, in the vicinity of potteries, where broken 

 gypsum molds may be had for the asking. 



Burned lime, shell-lime and limestone. — Burned lime 

 and finely ground shell-lime and limestone have also been 

 tried as to their ability to conserve the nitrogen in 

 manure. As to the first of these, it could hardly be ex- 

 pected to prove efficient in this direction. It is well 

 known that quick lime has the abihty to expel ammonia 

 from its combinations, and in the manure it acts in a 

 similar manner and intensifies the escape of this sub- 

 stance. Ground shell-lime, ground limestone, and cal- 

 careous marl are more mild in their action. They en- 

 courage decay and subsequently, also, nitrification, but 

 they do not appear to decrease the loss of nitrogen. 

 There is an indication, none the less, that further in- 

 quiry may enable us to utilize mild lime with more or 

 less advantage if not in the conservation at least in the 

 more rapid transformation of nitrogen in manure. 



Superphosphate. — Superphosphate, like gypsum, has 

 received much attention in experiments on the conserva- 

 tion of manure nitrogen. Superphosphate is made from 

 phosphate rock or bone by treatment with sulfuric acid, 

 the resulting products being gypsum, insoluble lime 



