1907.] on Problems of Applied Chemistry. 569 



of its nitrogen in a useful shape. This, together with the question 

 how coal of poor quality is to l)e turned to a l)etter account, has l)een 

 tackled T)Y the equally indefatiga])le and intelligently directed energy 

 of Dr. Ludwig Mond, one of the benefactors of the Royal Institution. 

 His invention, the " power-gas," has already attained a large measure 

 of success, as is proved by the extent of the plants erected and 

 designed. Mond's process belongs to that class by which we approach 

 one of the greatest problems, for the time being, of applied chemistry ; 

 I mean the conversion of nitrogen from sources not yet opened out 

 into ammonia and nitrates. 



The immense importance of this latter problem lies in the fact 

 that it touches our most urgent want, our supply of food. The soil 

 of most countries, if tilled in the old manner, would not nearly suffice 

 for the production of the requisite amount of food for men and cattle, 

 while the limits of its producing capacity are being gradually nar- 

 rowed down by exhaustion. Sir William Crookes, in his address to 

 the British Association in 1808, has most forcibly drawn attention to 

 this. The importation of food-stuffs from other less thickly populated 

 countries can only modify, but not altogether extinguish, the danger 

 of ultimate shortness of food at some future date, possibly not so very 

 remote. It is certainly a great comfort to know that, with suitable 

 manuring, the soil may be forced to yield even better crops than it 

 would give in the virgin state, let alone in a condition impoverished 

 by centuries of tilling. But stable manure is nothing like sufficient 

 to attain that object, and we must turn to mineral fertilisers, 

 principally phosphates, potassium salts, and nitrogen compounds. 

 The two former classes of fertilisers are found in abundance in nature, 

 and there is no danger, apparently, of their being exhausted during 

 the next thousand years. 



But the case is very different with the mineral forms of nitro- 

 genous manures, i.e. ammonium salts and nitrates. For agricultural 

 purposes it does not make much difference whether we apply the 

 nitrogen in one or the other of these forms. The ammonia, 

 apart from insignificant quantities otherwise obtained, all comes from 

 the nitrogen of the coal, but up to about twenty years, ago only that 

 coal which was used in the manufacture of gas was made to yield 

 ammonia, and only one-sixth of its nitrogen was obtained in this form. 

 In all other uses of coal, where at least twenty times as much is 

 consumed as in the manufacture of gas, the nitrogen was simply sent 

 into the air. 



Quite recently, some progress has-rbeeu made in the way of 

 utilising some of this nitrogen as well. I have already mentioned 

 the Mond process, where some of the nitrogen is recovered in the 

 shape of ammonia : but this covers only one corner of the field. 

 In another section a good deal has been already achieved. In the 

 manufacture of coke, which is also a process of /destructive distilla- 

 tion, and entirely analogous to gas making, very much larger quantities 



