192 OF MANURE. 



partly as lactate of urea, and partly in a free state. 

 (Henry.) Now when urine is allowed to putrify 

 spontaneously, that is, to pass into that state in 

 which it is used as manure, all the urea in com- 

 bination with lactic acid is converted into lactate 

 of ammonia, and that which was free, into volatile 

 carbonate of ammonia. 



In dung-reservoirs well constructed and protected 

 from evaporation, this carbonate of ammonia is 

 retained in the state of solution, and when the 

 putrified urine is spread over the land, a part of 

 the ammonia will escape with the water which eva- 

 porates, but another portion will be absorbed by 

 the soil, if it contains either alumina or iron ; but 

 in general, only the muriate, phosphate, and lactate 

 of ammonia remain in the ground. It is these 

 alone, therefore, which enable the soil to exercise 

 a direct influence on plants during the progress of 

 their growth, and not a particle of them escapes 

 being absorbed by the roots. 



On account of the formation of this carbonate of 

 ammonia, the urine becomes alkaline, although it 

 is acid in ite natural state. When it is lost by 

 being volatilized in the air, which happens in most 

 cases, the loss suffered is nearly equal to one half 

 of the weight of the urine employed, so that if we 

 fix it, that is, if we deprive it of its volatility, we 

 increase its action twofold. The existence of car- 

 bonate of ammonia in putrified urine long since 

 suggested the manufacture of sal-ammoniac from 



