530 Lord Rayleigh [April 5, 



long as the water remains in position, no leak can have occurred 

 through the insulating tubes conveying the electrodes. 



Now, if we switch on the current and approximate the points 

 sufficiently, we get the electric flame. There you have it. It is, at 

 present, showing a certain amount of soda. That in time would 

 burn off. After the arc has once been struck, the platinums can be 

 separated ; and then you have two tongues of fire ascending almost 

 independently of one another, but meeting above. Under the in- 

 fluence of such a flame, the oxygen and the nitrogen of the air 

 combine at a reasonable rate, and in this way the nitrogen is got 

 rid of. It is now only a question of boxing up the gas in a closed 

 space, where the argon concentrated by the combustion of the nitrogen 

 can be collected. But there are difficulties to be encountered here. 

 One cannot well use anything but a glass vessel. There is hardly 

 any metal available that will withstand the action of strong caustic 

 alkali and of the nitrous fumes resulting from the flame. One is 

 practically limited to glass. The glass vessel employed is a large 

 flask with a single neck, about half full of caustic alkali. The elec- 

 trodes are carried through the neck by means of an indiarubber bung 

 provided also with tubes for leading in the gas. The electric flame 

 is situated at a distance of only about half an inch above the caustic 

 alkali. In that way an efficient circulation is established; the hot 

 gases as they rise from the flame strike the top, and then as they 

 come round again in the course of the circulation they pass sufficiently 

 close to the caustic alkali to ensure an adequate removal of the 

 nitrous fumes. 



There is another point to be mentioned. It is necessary to keep 

 the vessel cool ; otherwise the heat would soon rise to such a point 

 that there would be excessive generation of steam, and then the 

 operation would come to a standstill. In order to meet this difficulty 

 the upper part of the vessel is provided with a water-jacket, in which 

 a circulation can be established. No doubt the glass is severely 

 treated, but it seems to stand it in a fairly amiable manner. 



By means of an arrangement of this kind, taking nearly three 

 horse-power from the electric supply, it is possible to consume 

 nitrogen at a reasonable rate. The transformers actually used are the 

 " Hedgehog " transformers of Mr. Swinburne, intended to transform 

 from 100 volts to 2400 volts. By Mr. Swinburne's advice I have used 

 two such, the fine wires being in series so as to accumulate the elec- 

 trical potential and the thick wires in parallel. The rate at which the 

 mixed gases are absorbed is about seven litres per hour ; and the 

 apparatus, when once fairly started, works very well as a rule, going 

 for many hours without attention. At times the arc has a trick of 

 going out, and it then requires to be restarted by approximating the 

 platinums. We have already worked 14 hours on end, and by the 

 aid of one or two automatic appliances it would, I think, be possible 

 to continue operations day and night. 



The gases, air and oxygen in about equal proportions, are mixed 



