DISCOVERY 



213 



1915 the British Government, in their difficulty, turned 

 to the Shawinigan Water and Power Companj', to see 

 whether calcium carbide could not again be called in 

 to help in an emergency, as it had already done in the 

 case of nitrogen from the air. At the time a good deal 

 of hterature existed dealing with synthetic methods 

 of preparing acetone and similar products from 

 acetylene, but hitherto no attempt had been made to 

 produce the former on a commercial scale. Experi- 

 mental work was started in December of that year, 

 and after six months the construction of the plant was 

 begun. In January 1917 acetone was being shipped 

 to Europe. Wliat a marvellous achievement when 

 one thinks of it : acetone from coke and lime ! — 

 it reads like some tale from the Arabian Niglils. The 

 process, the main outhnes only of which can be given 

 here, falls naturally under five heads. 



In the first place, acetylene had to be produced 

 from the carbide in very much larger quantities than 

 had ever been done before — some five or six hundred 

 thousand cubic feet per day, in itself no mean achieve- 

 ment. Secondly, large quantities of mercuric oxide 

 were required as a catal3St,' and this had to be made 

 by the cheapest method possible. An entirely new 

 electrolytic process was devised. The oxide of mercury 

 was removed, as it was formed, in suspension in caustic 

 soda, which was used as the electrolyte. The oxide 

 was then allowed to settle out, which did not take 

 long, as it is very heavj', the caustic soda being used 

 again. 



The third operation was the most difficult of all : the 

 acetylene was passed into sulphuric acid in which the 

 catalyst, the mercuric oxide, was suspended. Under 

 these circumstances another gas, acetaldehyde, was 

 formed, and this was drawTi off with the unused 

 acetylene, and separated from the latter by condensa- 

 tion by cooling to a low temperature. 



The next step was a comparatively simple one : it 

 consisted of oxidising the aldehyde to acetic acid. 

 For this purpose oxygen is required, and as it was 

 found impossible to get Linde-compressors for this 

 purpose, air had to be utihsed and a means devised 

 whereby the oxygen could be extracted. Here again 

 a catalyst had to be discovered. Large quantities of 

 nitrogen were liberated as a result of this operation, 

 which no doubt will be made use of one day to make 

 cyanamide. The matter, however, was not of sufficient 



' As the whole process depends, like so many other synthetic 

 methods, on the proper use of catalysts, it may be as well to 

 explain exactly what is meant by this term. 



By a "catalyst " the chemist means a chemical or some similar 

 substance which helps on the reaction, but is itself left practi- 

 cally in the same condition at the end as at the start of the 

 proceedings. Nearly all industrial proc.esses depend in some 

 way or other on the careful choice of a catalyst; the whole 

 subject has been very carefully studied of late years. 



importance during the war to mal<e it worth while 

 recovering this waste product ; all energies had to be 

 devoted to the production of the acetone. 



Having arrived at the acetic acid stage, it only 

 remained, in the fifth and last step, to obtain acetone 

 from this material ; and here, again, this involved the 

 discovery of a suitable catalyst, that would bring about 

 the change. After a number of experiments, hydrated 

 lime, with a httle magnesia, was found to give the 

 best results. 



Cast-iron baUs were coated with a wet paste made 

 of these materials, and they were then placed in a long 

 tube which could be electrically heated. After drying 

 the catalyst on the balls, the vaporised acetic acid 

 was passed through the heated tubes at 485° C, and it 

 was found that the conversion into acetone was well- 

 nigh complete. Some seventy-two of these tubes were 

 installed, capable of producing some ten tons of 

 acetone a day. The products from the tubes were 

 then passed through a soda-ash scrubber, to remove 

 the small quantity of unchanged acetic acid, which 

 amounted to some 5 per cent. The acetone, after 

 washing, was finally rectified in the usual way. 



The cost of production of acetone from carbide was 

 found to be much greater than ordinary commercial 

 conditions would permit ; and had it not been for the 

 urgent need of this spirit by the British Government, 

 the process might never have been carried through to 

 its ultimate conclusion. It was not, therefore, a matter 

 for deep regret when it was learnt that the need for 

 acetic acid was greater than the need for acetone, and 

 a request was received that they would export the 

 former in place of the acetone, which was at first 

 required. The need for acetic acid arose from the 

 enormous demands made on this material for making 

 cellulose acetate, which is used in dope for aeroplane 

 wings. 



From November 1917 onwards to the present time, 

 the plant has accordingly been used entirely for 

 the production of acetic acid, and, when America 

 came in, a second plant was erected for the United 

 States Government for the same purpose. At the 

 signing of the Armistice this plant was just complete, 

 and the two together would have been capable of pro- 

 ducing some 1,600 tons of acetic acid per month. 

 To-day the company is manufacturing synthetic 

 acid on a commercial scale, and are able to compete 

 very favourably on the open market. The purity of 

 the acid, which is well over 99 per cent., is a point 

 greatly in its favour. As to the future of other syn- 

 thetic products which could conceivably be made 

 from acetic acid, time alone wUl show whether they 

 could be made a commercial success. There is no 

 doubt but that developments could be made along 

 the same lines as those for the production of acetone. 



