NITROGEN AS AMMONIA 213 



By proper appliances the escaping gases from coke ovens 

 or gas retorts are led through water in which the ammonia 

 is dissolved. It is then distilled bv steam with the addi- 

 tion of lime to break up ammonium compounds, and led 

 into sulphuric acid. The solution of ammonium sulphate is 

 evaporated and the white or gray salt which results is dried 

 and sold as sulphate of ammonium, largely for fertilizing 

 purposes. 



(6) Availability. — Ammonium sulphate is almost as solu- 

 ble as sodium nitrate, one part dissolving in about one and 

 one-third parts of water, but for most plants it is not the best 

 form of nitrogen. The ammonia nitrogen must first change 

 to nitrate nitrogen which it does very rapidly in the soil 

 by the process called nitrification (Section 128). Its ready 

 solubility and rapid change to nitrate make it only slightly 

 less readilv available than sodium nitrate, and it is ranked 

 as a quick-acting fertilizer. In the early spring, however, to 

 start wheat, for example, ammonium sulphate is not good 

 because at that time of year bacterial action is very slow 

 and nitrification does not take place with sufficient rapidity 

 to feed the crop. A nitrate is better under these conditions. 



Ammonia nitrogen is not leached from the soil as rapidly 

 as nitrate nitrogen, being absorbed both chemically and 

 physically (Section 137). Ammonia, held either in other 

 chemical combinations or absorbed bv humus or hvdrated 

 silicates, is just as easily nitrified as it is in the sulphate 

 form. Until nitrified, ammonium sulphate is not lost from 

 the soil, but nitrification is ordinarily so rapid that ammo- 

 nium sulphate is not a lasting nitrogenous fertilizer. 



(c) Effect on the Soil.— Whereas sodium and calcium 

 nitrates tend to produce a residual alkaline condition of 

 the soil, ammonium sulphate tends to produce an acid con- 

 dition. Long continued use of this form of nitrogen results 

 in a very acid condition of the soil. On the fertilizer plats 

 of the Pennsylvania Experiment Station the use of 72 pounds 

 of nitrogen as ammonium sulphate per acre once in two years 

 for thirty years has resulted in a soil which needs 19 times 

 as much lime to correct the acidity as do the check plats 

 receiving no fertilizer. 



