302 SMITH'S INTERMEDIATE CHEMISTRY 



(6 to 8 per cent) removed either by refrigeration or by absorption 

 in water. The residual nitrogen and hydrogen are returned to 

 the plant for further treatment. 



The ammonia obtained is used, in times of peace, mainly in 

 the manufacture of fertilizers, such as ammonium sulphate. In 

 war times, however, it is required more urgently for the produc- 

 tion of explosives. Nitric acid HNQs, which is necessary in the 

 preparation of most explosives, is obtained from ammonia by 

 oxidation (see p. 313). By the neutralization of nitric acid with 

 ammonia, ammonium nitrate NH 4 N0 3 is formed. A mixture of this 

 substance with trinitrotoluene (p. 483) was used extensively as a 

 high explosive during the Great War, under the name of amatol. 



Synthetic ammonia may also be prepared by the calcium 

 cyanamide process (see p. 392). But for these two processes, 

 Germany would never have been able to continue fighting in 

 the Great War beyond the first year. With all foreign supplies 

 of nitrates (Chili saltpeter) cut off, the only other available source 

 of ammonia was the by-product coke industry, and this was 

 already being utilized almost to its maximum. In the allied 

 countries, unfortunately, the Haber process during the war was 

 not developed beyond the experimental stage. 



The productive capacity of Haber process plants in 1920 was 

 no less than one and a half million tons (calculated as ammonium 

 sulphate). 



Preparation in the Laboratory. In the laboratory am- 

 monia is most readily made by heating a mixture of a salt of 

 ammonium, such as the chloride (NH 4 C1) or sulphate, and slaked 

 lime Ca(OH) 2 . 



Ca(OH) 2 + 2NH 4 C1 -> CaCl 2 + 2NH 4 OH -> 2NH 3 + 2H 2 O. 

 The ammonium hydroxide, formed by the double decomposition, 

 immediately decomposes. To free the gas from water vapor, it is 

 passed through a tower filled with quicklime CaO (Fig. 78) : 



H 2 0-Ca(OH) 2 . 





