FIXATION OF AMMONIA. 191 



fied urine is spread over the land, a part of the am- 

 monia will escape with the water which evaporates, 

 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 its 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 carbonate of 

 ammonia in putrefied urine long since suggested the 

 manufacture of sal-ammoniac from this material. 

 When the latter salt possessed a high price, this 

 manufacture was even carried on by the farmer. For 

 this purpose the liquid obtained from dunghills was 

 placed in vessels of iron, and subjected to distilla- 

 tion ; the product of this distillation was converted 

 into muriate of ammonia by the common method. 

 (Demachy.) But it is evident that such a thought- 

 less proceeding must be wholly relinquished, since 

 the nitrogen of 100 lbs. of sal-ammoniac (which con- 

 tains 26 parts of nitrogen) is equal to the quantity 

 of nitrogen contained in 1200 lbs. of the grain of 

 wheat, 1480 lbs. of that of barley, or 2755 lbs. of 

 hay. (Boussingault.) 



The carbonate of ammonia formed by the putrefac- 

 tion of urine, can be fixed or deprived of its volatil- 

 ity in many ways. 



If a field be strewed with gypsum, and then with 

 putrefied urine or the drainings of dunghills, all the 

 carbonate of ammonia will be converted into the sul- 

 phate which will remain in the soil. 



