706 



SCIENCE. 



[N. S. Vol. I. No. 26. 



require to be very massive on account of the 

 the heat evolved. In this case they consist 

 of platinum wire doubled upon itself six 

 times. The platinums are continued by 

 iron wires going through glass tubes, and 

 attached at the ends to the copper leads. 

 For better securitj^, the tubes themselves 

 are stopped at the lower ends with corks 

 and charged with water, the advantage be- 

 ing that, when the whole arrangement is 

 fitted by means of an indiarubber stopper 

 into a closed vessel, you have a witness that, 

 as long as the water remains in position, no 

 leak can have occurred through the insul- 

 ating tubes conveying the electrodes. 



Now, if we switch on the current and ap- 

 proximate 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 ofi". After 

 tbe arc has once been struck, the platinums 

 can be separated ; and then you have two 

 tongues of fire ascending almost independ- 

 ently of one another, but meeting above. 

 Under the influence of such a flame the oxy- 

 gen and the nitrogen of the air combine at 

 a reasonable rate, and in this way the ni- 

 trogen is got rid of. It is now only a ques- 

 tion of boxing up the gas in a closed space, 

 where the argon concentrated by the com- 

 bustion of the nitrogen can be collected. 

 But there are difficulties to be encountered 

 -bere. One cannot well use anything but a 

 glass vessel. There is hardly any metal 

 available that will withstand the action of 

 sti'ong caustic alkali and of the nitrous 

 fames resulting from the flame. One is 

 practically limited to glass. The glass ves- 

 sel employed is a large flask with a single 

 neck, about half full of caustic alkali. The 

 electrodes are carried through the neck by 

 means of an indiarubber bung provided al- 

 so 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 around again in the course of 

 the circulation they pass sufficiently close 

 to the caustic alkali to insure 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 genera- 

 tion 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 it in a fairly amiable manner. 



Bj' means of an arrangement of this kind, 

 taking neai-ly three-horse power fi-om the 

 electric supply, it is possible to consume 

 nitrogen at a reasonable rate. The trans- 

 formers actually used are the ' Hedgehog ' 

 transformers of Mr. Swinburne, intended to 

 transform from 100 to 2400 volts. By Mr. 

 Swinburne's advice I have used two such, 

 the fine wires being in series so as to accu- 

 mulate the electrical 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 atten- 

 tion. 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 in a large gasholder, 

 and are fed in automatically as requii-ed. 

 The argon gradually accumulates ; and 

 when it is desired to stop operations the 

 supply of nitrogen is cut off, and onlj^ pure 

 oxygen allowed admittance. In this way 



