4 o8 ACETYLENE 



members of the paraffin and ethylene series, such 'as ethane, propane, butane, ethylene, 

 propylene, etc., of high illuminating power, and by cooling and compressing these under 

 high pressure in a steel cylinder they are liquefied, whilst the hydrogen and methane 

 remain gaseous and pass on. This liquid gasifies entirely when the valve of the cylinder 

 is opened, and constitutes the " Blau gas," and is largely used when high light values 

 are needed from jets or flat flame burners. 



Of late years there has been a great influx of so-called " air 7 gas " or " petrol air gas " 

 machines on the market, intended for the lighting of country houses where coal gas or 

 electricity is not available. In nearly all these the principle first introduced by Hooker 

 of adding only enough petrol vapour to the air to make it combustible and not enough to 

 make it explosive, has been adopted, so that any leakage of the gas, instead of forming 

 an explosive mixture as would be the case with coal gas, becomes non-combustible from 

 over-dilution. The principle of all the machines is to evaporate a given weight of petrol 

 into a definite volume of air, and to bring this about a large number of automatic devices 

 are employed, driven by water power, hot air engines or falling weights. The " gas " 

 so formed consists of a mixture of about 98 per cent of air with 2 per cent petrol vapour, 

 and burns in specially constructed burners as a non-luminous flame which is used with an 

 incandescent mantle. A gallon of petrol in a good machine will make from 1400 to 1500 

 cubic feet of " gas," having a heating value of between 80 and 90 B Th U per cubic foot. 



(VIVIAN B. LEWES.) 



ACETYLENE 1 



The progress of the past two years in the use of acetylene has been chiefly in the direc- 

 tion of oxy-acetylene welding and cutting. As an illuminant, the number of new instal- 

 lations in Great Britain keeps a steady average. In other countries, where central in- 

 stallations for the lighting of small towns and villages are more often met with, the in- 

 crease is more marked. Welding and cutting by means of the oxy-acetylene blowpipe, 

 however, is advancing with great rapidity, America leading the way both in quantity and 

 quality of the work done; Germany occupies the second place, France the third, and the 

 United Kingdom a bad fourth. A school of acetylene welding has however been started 

 in England, and more rapid progress is expected. 



A noticeable feature is that in France and Germany nearly two-thirds of the oxy-acetylene 

 welding done is in manufacturing work, while in America the extreme value of the process 

 for rapid repairs has been fully realised, and nearly three-quarters of the work 

 done is of that character. The size of the work which can now be undertaken 

 nas enormous ly increased with extended knowledge of the requirements, and 

 two examples will suffice to indicate the saving that can be effected by the 

 rapidity with which the work is done. A section of the frame of a steam hammer, weighing 

 about four tons, was fractured, and by means of the oxy-acetylene torch new metal was 

 filled into the break, the whole of the welding completed, and the section delivered within 

 48 hours. The "Commonwealth," a large passenger steamer, was in collision with a warship 

 and had her bows badly crumpled up, but by the oxy-acetylene cutting torch the damaged 

 portion was removed, the repairs executed, and service resumed within a week. 



In the early days of welding by the oxy-acetylene blowpipe many cases occurred which 

 seemed to point to the steel being rendered hard and brittle in the neighbourhood of the 

 heated portion. Investigation however has shown that this is due to careless adjustment 

 of the ratio of acetylene to oxygen in the blowpipe flame, which with any excess of acetylene 

 increased the carbon in the steel and so hardened it, and that if a properly designed and 

 adjusted blowpipe is used the tensile strength of test pieces cut from a plate with the oxy- 

 acetylene flame is higher than when sheared. Some recent Austrian experiments on two 

 mild steels however show that when a chrome nickel steel, hardened for armour plate, is 

 cut by the flame a softening of the steel takes place, this being most noticeable close to the 

 cut and gradually diminishing as the distance became greater, whilst a nickel steel, un- 

 hardened, was perfectly unaffected. 



The American Naval Department was one of the first to adopt the oxy-acetylene process, 

 and in building one of the recent battleships expended over 870,000 in welding and cutting 

 by it. The system has also been adopted widely at many European ports, and at Marseilles, 

 Genoa and Antwerp has been in use for several years. The use of acetylene dissolved in 

 acetone under pressure, the acetone being contained in porous material packed into strong 

 steel cylinders, has largely extended the scope of autogenous soldering, as both acetylene 



1 See E. B. i, 137 et seq. 



