UTILISATION OF GASES 67 



Another quite recent application of gases is that dealing with 

 the cutting and welding of metals, in which use is made of the high 

 temperature produced by the combustion of various gases with 

 oxygen. The temperature obtained varies with the gas employed, 

 and until recently the hottest blow-pipe flame was the oxy-hydrogen, 

 which gives a temperature of about 4000°F. It has been found, 

 however, that a much more intense heat is obtainable by the com- 

 bustion of acetylene, and with the oxy-acetylene blow-pipe a 

 temperature of 6300° F. is reached. Quite a new field has been 

 opened up in the working of metals by the development of the 

 oxy-acetylene blow-pipe, since metals such as iron and steel can 

 be fused with the greatest facility. 



Instead of using rivets, metal joints are now often made by 

 fusing the ends of the metal together ; cracks in metal castings and 

 in working machinery are being repaired by cutting out the cracks 

 and then filling them up with metal fused from a stick of the same 

 by the oxy-acetylene blow-pipe, the whole process resembling 

 soldering. Damaged boilers and steam pipes are now being re- 

 paired in situ. 



The oxy-acetylene blow-pipe is also being extensively used for 

 cutting metal, in which case an excess of oxygen is supplied to the 

 blow-pipe, so that not only is the metal melted, but at the high 

 temperature of the flame a considerable portion of it is actually 

 burnt by the oxygen. It is indeed a wonderful sight to see a thick 

 plate of steel cut through by an oxy-acetylene flame with the greatest 

 ease, 



I have not time to dwell upon the many other important apph- 

 cations of gases in modern life, such us the utilization of hydrogen 

 gas for filling the envelopes of air-ships and in the manufacture of 

 filament lamps ; the use of oxygen and nitrous oxide gases in 

 medicine, and of carbonic acid gas for aerating water ; but I hope 

 I have already said enough to impress upon my audience, if they 

 were not already aware of it, the very important functions filled 

 by gases in the industrial life of the present day. 



In my work during the last few years I have been brought into 

 contact in several ways with problems concerning the utilisation 

 of gases, and have always found the subject interesting, and before 

 actually closing this paper I should hke to mention one or two 

 minor uses to which, I think, gases might be put, although such 

 matter really falls outside the scope of the paper. 



\yhile investigating the use of flue gas for fire-extinction 

 purposes I carried out some experiments to determine the best 

 means of displacing the air from a closed space by means of this 

 gas. Into a vessel of known capacity an equal volume of flue 

 gas was passed and the percentage of oxygen in the residual 

 atmosphere was determined. Knowing the content of the flue gas 

 in oxygen I was able to ascertain just how much air had been 

 driven out of the vessel and how much remained mixed with flue 

 gas. My experiments, performed on a small scale in glass jars, 



