226 CHEMICAL FERTILIZERS 



with the formation of cyanide and cyanamide of barium, 

 which give off ammonia on passing in steam. Up to the 

 present, little practical use has been made of this method, 

 but in the future it may come into more prominence. 



The Serpek Process. Alumina, carbon and nitrogen 

 give aluminium nitride, which, on treatment with caustic 

 soda, gives ammonia, 



A1N + 3NaOH = NH 3 + Na 3 AlO 3 



Pure alumina for the manufacture of aluminium can be made 

 in this way. The success of this method is entirely dependent 

 on the market for the pure alumina produced from crude 

 minerals. 



By-Product Ammonia. As time goes on, and greater 

 care is taken of coal, a larger proportion of the nitrogen in 

 coal will be recovered in the form of ammonia. In Great 

 Britain, there is an almost certain decrease in the production 

 of coal, and a further decrease in the consumption, owing to 

 the necessity of cutting down fuel costs. Other parts of the 

 world are, however, increasing their production of coal and 

 coal products. In the manufacture of compound fertilizers, 

 ammonium sulphate will continue to be the most suitable 

 standard article. Ammonium nitrate might be produced, 

 but it is rather doubtful whether much advantage would 

 result, as it is too concentrated for ordinary use on the land, 

 and does not lend itself to mixtures. All the countries 

 engaged in war have invested very large sums of money in 

 nitrogen fixing plant, and many of these may continue to 

 produce nitrogen compounds, so that there should be ample 

 supplies of nitrogen compounds for agricultural and industrial 

 purposes. In estimating the relative values of the different 

 forms of nitrogen products, by-product ammonia always 

 stands out as an article which must be produced, and there is 

 no price so low as to stop its production (see p. 189). 



Nitrogen Fixation on the Land. The fixation of 

 nitrogen in the soil is greatly increased by the growth of 

 leguminous crops, which are encouraged by the employment 

 of phosphatic manures. Much extended development on 



