212 



DISCOVERY 



evolution of a vcn,' poisonous gas, carbon monoxide, 

 which fortunately soon finds some more oxygen in 

 the air with which to combine to form the harmless 

 gas, carbon dioxide, that we exhale. The chemist 

 expresses these changes very simply by the two 

 equations ; 



CaO + 3C 



(Calcium (Carbon, 



Oxide, or or 



Lime ) Coke) 



CaC, + CO 

 (Calcium (Carbon 



Carbide) Monoxide) 



CO + O = CO, 

 (Carbon (Oxygen) (Carbon 



Monoxide) Dioxide) 



At first the newly discovered carbide was merely used 

 for generating acetylene for lighting purposes; and 

 even for this many brains had to be racked and many 

 inventions made to find out how to burn the gas 

 without the smokiness of the flame, and how to generate 

 it to get a constant supply without fear of explosion. 

 The advantages of the gas for lighting railway trains, 

 vehicles, etc., soon became apparent, and it was not 

 long before its use was adapted for lighting isolated 

 houses in the country. In England it has not gone 

 much further than this stage, but in the United States 

 and Canada it is not at all uncommon to find small 

 townships supplied with the gas as a municipal enter- 

 prise. 



The next step in the history of carbide was the 

 discovery that acetone would dissolve about twentj'- 

 four times its own volume of acetylene at ordinary 

 temperature and pressure, and very much more when 

 compressed, thus affording a ready and safe means 

 of transporting the gas in a handy manner. Iron 

 cylinders packed with asbestos rings soaked in acetone 

 were constructed, and the gas pumped in imder pressure. 

 With what to all intents and purposes was solid 

 acetylene, it was not long before an entirely new use 

 was found for the gas — namely, as a substitute for 

 the hydrogen in the oxy-hydrogen blowpipe or torch, 

 as it is sometimes called. Acetylene, even when it 

 burns in the air, gives a very hot flame, but when 

 oxygen is substituted for the air, the heat of the 

 flame is greatly intensified. The temperature of 

 the oxy-acetylene flame is estimated at anything 

 between 6,000° and 7,000° Fahrenheit. The process 

 of oxy-acetylene welding, in which these torches are 

 used, dates from 1903, and has found a hundred 

 different uses since then ; and as a direct outcome of 

 it, a still newer process, that of the " cutting blowpipe," 

 may be mentioned in passing. By means of the latter, 

 all forms of steel may be cut much in the same way 

 as the grocer cuts through a piece of cheese with a steel 



wire, and with as little effort. The heat is so intense 

 that the cut is clean, there being no time for the metal 

 to melt before the flame passes on. To-day, only 

 seventeen years after its invention, acetylene welding 

 and cutting has become a common feature of every 

 engineering shop and shipyard. 



In the March issue of this magazine, in an article 

 on the Source of Nitrogen, I told the story of how 

 carbide had come to our aid for this all-important 

 purpose ; how, when it was heated w^th nitrogen, 

 cyanamide was formed, from which all sorts of nitro- 

 genous products could easily be obtained. Great as 

 this discovery is, it seems but a little thing in com- 

 parison with the achievements of the chemists at 

 Shawinigan, in Canada, during the war. The cheap 

 electric power derived from the Falls of Shawinigan 

 had already made this spot the centre of the Canadian 

 chemical industry ; carbide was already being made 

 there on a large scale and of excellent quahty, and 

 many other allied industries had sprung up in the same 

 district. 



As has already been indicated, acetone is one of 

 the essentials in warfare, for it is used in the manu- 

 facture of cordite, the standard British explosive. 

 Cordite is not what is known as a high explosive, but 

 is used in enormous quantities for propelling the shells, 

 carrying the latter through the air. WTien one realises 

 that it is cordite which fills the body of the huge shells 

 used on our ships, one gets a faint idea of the demand 

 there must have been for this material, and conse- 

 quently for the acetone used in its manufacture. 

 Although acetone does not really enter into the con- 

 stitution of the finished cordite, but, hke the water used 

 in bread-making, really only assists in the mixing 

 process, it is found in practice that little more than 

 half can be recovered to be used again. There is little 

 wonder, under the circumstances, that the Government 

 soon found themselves at a loss for further supplies. 

 Acetone is normally obtained from the distillation of 

 calcium acetate, itself obtained from the destructive 

 distillation of wood. This source of supply was soon 

 found to be entirely unable to cope with the demands 

 put upon it. Desperate efforts were made to obtain 

 the precious liquid from any source whatever; fer- 

 mentation processes were resorted to, and any starch 

 products which could not be used for food, such as 

 spoilt rice, for instance, were turned to account. Even 

 village children were called in to assist, by collecting 

 horse chestnuts, throughout the length and breadth of 

 the country, and these were sent to the Government 

 cordite factory afHolton Heath, near Bournemouth, 

 in the hope that they would furnish a cheap and 

 otherwise useless source of starch ; the difficulty of 

 getting at the starch through the various integuments 

 of the nuts, however, proved insuperable. Late in 



