40 A. Killen Macbeth on 



tive. A prior place may be given to the process of acid 

 manufacture. It has been said that the wealth of a nation may- 

 be gauged by studying its consumption of sulphuric acid. This 

 acid is extensively employed in manufacturing operations and so 

 the quantity used gives an indication of the commercial activities 

 of a nation. The acid results from a solution of sulphur trioxide 

 in water. When sulphur (or an ore containing a high percentage 

 of sulphur) is burnt in air, a gas known as sulphur dioxide is 

 obtained. This unites with oxygen to form the trioxide. The 

 manufacture of sulphuric acid therefore centres round the 

 question of an effective process for combining sulphur dioxide 

 with atmospheric oxygen. This is brought about by two 

 processes, both of which involve the use of a catalyst. The 

 Chamber Process depends on the catalytic power of nitrogen 

 peroxide which has already been referred to. The Contact 

 Process rests on the action of various agents, which promote the 

 union of the gases when the mixture is passed over layers of the 

 catalyst. Iron oxide is found to induce a sixty per cent, union 

 of sulphur dioxide and oxygen if the temperature is about 600'^C. 

 Asbestos impregnated with a solution of platinic chloride (known 

 as platinised asbestos) is a much more effective, but more 

 expensive, agent. An interesting point may be noted in this 

 cormection. If the gaseous mixture contains certain impurities — 

 notably arsenic — the efficiency of the catalyst rapidly decreases 

 and in time its power disappears completely. This is referred to 

 as poisoning of the catalyst and is a point which demands much 

 attention in all catalytic processes. 



The Nitrogen Question — The, next operation which may 

 be described deals with the manufacture of ammonia and nitric 

 acid. It has been said that the fate of a nation probably rests 

 on two simple compounds of nitrogen — ammonia and nitric acid. 

 This seems a very remarkable statement and deserves examination. 

 Taking a wide view of the matter we might say that the three 

 chief factors in a nation's life are her commerce, her armaments 

 and her food production. Without her commerce she must 



