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J\.KPoRi S.A.A. Advancement of Science. 



some une whose eyes are not blinded by routine comes along, sees- 

 the practical application, and applies it accordmgl). A parallel 

 case is that of the extraction of gold by means of c\anide. an ex- 

 periment which thousands have carried out \ears and years ago. 

 MrArthur was far-seeing, and applied it in a \va\ which has been of 

 incalculable benefit to South Africa, liut not much good to himself. 



The chamber process for making sul])huric acid is roughly as- 

 follows : — Suljjhur or i:)yrites is burned in o\cns, and SC)^ is produced. 

 This gas is carried into large lead chambeis. together with some 

 oxides of nitrogen. Water is also injected as steam. The nitrogen 

 oxide being what we call an oxidising body hands ov(.:r part of its 

 oxygen to the SO2, producing SO3, which in turn coml)incs with the 

 water present, forming sulphuric acid, of a diluted kijid. called 

 chamber acid. This has to be concentrated u[) till it contains 

 96% H2SO4. and, among other things, 1 may mention that our 

 platinum stills for this purpose represent a value of __;^i 00,000. 

 The contact process aims at producing stro)ig acid right away, thus- 

 saving all the cost of concentration. Sulphur or pyrites, as in the 

 chamber process, is burned in ovens, and the SO2 produced, 

 together with atmospheric oxygen, is passed over a catal\tic agent 

 — generallv finely divided platinum — which causes (hem to combine, 

 forming SO3. The neces.sary amount of water can be added in. 

 many ways, but in any case strong acid is produced right off. 



This also sounds simple, Init the working out of the process- 

 to its present state of perfection has involved )ears of most patient 

 research, and it is perhaps the best example extant of the mutual 

 inter-dependence of the engineer and the chemist. 



I have started with sulphuric acid, for it is required in order tO' 

 make nitric acid, which is also a simple o])eralion, chemically speak- 

 ing, but which in recent years has become entirely revolutionised 

 by modern imj)rovements. Nitric acid, as \ou know, is made by 

 distilling a mixture of nitrate of sorlu and sul|)Iiuric acid. It is. 

 unfortunate that up to now the onl) deposit of nitrate of soda of 

 any commercial imjiortance is the world rcnowiunl one in Chili, 

 from which all manufacturers of e.\i)lo.-,i\cs have to draw their 

 supplies. 



Now that we have seen to our raw materials, we can start awav 

 on the manufacture of nitro-glycerine. Sulj)htijic and nitric acids- 

 are first of all mixed roughly in the proportion of two of the former 

 to one of the latter, and when this is done, gbccrine is dropped or 

 sprayed into the mixture. A large amount of heat is evolved, and' 

 in order to keep down the temperature, cold water is constantlv 

 kept circulating through coils in the body of the apparatus. I 

 have already said that the acids must be as strong as possible, and' 

 the sulphuric acid is pre.sent only to take up the water formed in 

 the reaction. Not so very long ago the amount of glycerine used 

 in each charge or operation was comparativeb small. 'but nowadays- 

 about a long ton of nitro-gl)cerine is made at one charge. About 

 220 parts of nitroglycerine are obtained from e\ery'ioo parts- 

 of glycerine. I need not take you through all the side processes, as 



