JUXK 13, 1895] 



NA rURE 



161 



amounletl to about , i j part of the nitrogen taken ; and Cavendish 

 draws the conclusion that if there be more than one inert in- 

 gredient in the atmosphere, at any rate the second ingredient is 

 not contained to a greater extent than yi^ part. 



I must not wait too long over the experiment. Mr. Gordon 

 tells me that a certain amount of contraction has already 

 occurred ; and if we project the U upon the screen, we sliall 

 be able to verify the fact. It is only a question of time for the 

 greater part of the gas to be taken up, as we have proved by 

 preliminary experiments. 



In what I have to say from this point onwards, I must l)e 

 understood as speaking as much on behalf of Prof. Kamsay as 

 for myself. At the first, the work which we did waste a certain 

 extent independent. .\fterwards we worked in concert, and 

 all that we have published in our joint names must be regarded 

 as being equally the work of both of us. But, of course, l*rof. 

 Ramsay must not be held responsible for any chemical bluniler 

 into which I may stumble lo-night. 



liy his work and by mine the heavier ingredient in atmo- 

 spheric nitrogen which was the origin of the discrepancy 

 in the densities has been isolated, and we have given it 

 the name of " argon." For this purpose we may use the 

 original method of Cavendish, with the advantages of modern 

 appliances. We can procure more powerful electric sjwrks 

 than any which Cavendish could command by the use of the 

 ordinary Ruhmkorff coil stinudated by a battery of drove 

 cells ; and it is possible so to obtain evidence of the existence of 

 argon. The oxidation of nitrogen by that method goes on ]iretty 

 quickly. If you put some ordinary air, or, better still, a mixture 

 of air and oxygen, in a tube in which electric sparks are made to 

 pass for a certain time, then in looking through the tube you 

 observe the well-known reddish-orange fumes of the oxides of 

 nitrogen. I will not take up time in going through the experi- 

 ment, but will merely exhibit a tube already prepared (image on 

 screen). 



One can work more efficiently by employing the alternate cur- 

 rents from dynamo machines which are now at our command. 

 In this Institution we have the advantage of a ]>ublic supply ; 

 and if I pass alternate currents originating in I)eiitfi>rd through 

 this Kuhmkorff coil, which acts as what is now called a *' high 

 potential transformer," and allow sparks from the secondary to 

 |)ass in an inverted test tube between platinum pf)ints. we shall 

 be able to show in a comparatively short time a pretty rapid ab- 

 sorption of the gases. The electric current is led into the »c)rking 

 chamber through bent glass tubes containing mercury, and pro- 

 vided at their inner extremities with platinum points. In this 

 arrangement we avoid the risk, which woidd (Otherwise be serious, 

 of a fracture just when we lea.st desired it. I now ^tart the 

 sparks by switching on the Kuhmkorff to the alternate current 

 .supply ; and, if you will take note of the level of the liquid 

 representing the quantity of mixed gases included, I think you 

 will see after, perhaps, a quarter of an hour that the lii)uid h,as 

 very appreciably risen, owing to the union of the nitrrjgen and the 

 oxygen gases under the influence of the electrical discharge, and 

 subseipient absorption of the resulting compound by the alkaline 

 liquid with which the gas sp.ice is enclosed. 



By means of this little apparatus, which is very convenient for 

 operations upon a moderate scale, such as for analyses of 

 "nitrogen" for the amount of argon that it may cimtain, wc 

 are able to get an absorption of about 80 cubic centimetres per 

 hour) or about 4 inches along this lest tube, when all is going 

 well. In order, however, to obtain the isolation of argon on 

 any considerable scale by means of the oxygen method, we must 

 employ an apparatus still more enlarged. The isolation of 

 argon requires the removal of nitrogen, and, indeed, of very 

 Urge quantities of nitrogen, for, as it appears, the proportion 

 of argon contained in atmospheric nitrogen is oidy about I per 

 cent., so that for every litre of argon that you wi.sh to get you 

 must eat up some hundred litres of nitrogen. That, however, 

 can be done upon an adequate scale by calling to our aid the 

 powerful electric discharge now obtainable by means of the 

 alternate current supply and high potential transformers. 



In what I have done upon this subject I have had the ad- 

 vantage of the advice of Mr. Crookes, who some years ago 

 drew special attention to the electric discharge or Hanie, and 

 showed that many of its properties ilepended upon the fact thil 

 it had the power of causing, upon a very considerable scale, a 

 combin.ation of the nitrogen and the oxygen of the air in which 

 it was made. 



I had first thought of showing in the lecture room the actual 



NO. 1337, VOL. 52] 



apparatus whicli I have employed for the concentration of argon : 

 but the ilifticully is that, as the apparatus has to Ix- used, the 

 working parts are almost invisible, and I came to the conclusion 

 that it would really be more instructive as well as more con- 

 venient to show the parts isolated, a very little eflbrt of imagina- 

 tion being then all that is required in order to reconstruct in the 

 mind the actual arrangements employed. 



First, as to the electric arc or flame itself. We have here a 

 transformer made by I'ike and Harris. It is not the one that I 

 have used in practice : liut it is convenient for certain purposes, 

 and it can lie connected by means of a sw itch with the alternate 

 currenis of 100 volts furnished by the Supply Company. The 

 platinum terminals that you .see here are ritodelled exactly upon 

 the plan of those w hich have been employed in practice. I may 

 say a word or two on the question of mounting. The terminals 

 require to be very massive on account of the heat evolved. In 

 this case they consi.st of platinum wire doubled upon itself six 

 times. The platinums are contii u.'l by iron wires going through 

 glass tubes, and attached at the ends to the copper leads. For 

 better security, the tubes themselves are stop|ied at the lower 

 ends with corks and charged with water, the advantage being that, 

 when the whole arrangement is fitted by means of an india- 

 rubber stopper into a closed vessel, you have a witness that, as 

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

 through the insulating lubes con\*cying the electrodes. 



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

 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 of)', .\fter the arc has once been struck, the 

 platinums can be separated ; and then you have two tongues of 

 fire asceniling almost independently of one another, but meeting 

 above. Under the influence of such a flame, the oxygen ar.d 

 the nitrogen of the air combine at a reasonable rate, and in this 

 way the nitrogen is got ri<l of. It is now only a c|uestion of 

 boxing up the gas in a closed space, where the argon concentrated 

 by the combustion of the nitrogen can Iw collected. But there 

 are difficulties to be encountered here. One cannot well use 

 anything but a glass vessel. There is hardly an)' metal available 

 that will wilhstaiiil the action of strong caustic alkali and of the 

 nitrous fumes resulting from the flame, t )ne is i:)ractically 

 limited to glass. The glass vessel emph)yetl 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 also with lubes 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 circulatir.n is estab- 

 lished ; the hot gases as ihey rise from the flame strike the top, 

 and then as they come round again in the course of the circula- 

 tion they pass sufficiently close to the caustic alkali to ensure an 

 adequate removal of the nitrous fumes. 



There is another ]>oint to be mentioned. It is necessary to 

 keep the vessel cotil ; otherwise the heat would soon rise to such 

 a point that there would be excessive generiition of .steam, and 

 then the operation would come to a .standstill. In order to 

 meet this difficult}' 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 treatetl. 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 siqiply. it is possible to consume 

 nitrogen at a reasonable rate. The transformers actually used 

 are the " Hedgehog" Iransfijrmers of Mr. Swinburne, intended 

 to transform from too 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 electrical potential and the thick wires in 

 jrarallel. The rate at which the mixed gases are absorbed is 

 about seven litres jier hour : and the apparatus, when once 

 fairly slarteil, works very well as a rule, going for many hours 

 without attention. .\t times the arc has a trick of going out, 

 and it then requires to be restarted by approximating the 

 platinums. We have already worked fourteen hours on end. 

 and by the aid of one or two automatic appliances it would, I 

 Ihmk, be pos.sible to continue operations day and night. 



The ga.ses, air and oxygen in about equal pro]iortions, are 

 mixed in a large gasholder, and are fed in automatically as re- 

 required. The argon gradually accumulates ; and when it is 

 desired to .stop operalioEis the supply of nitrogen is cut oft', and 

 only pure oxygen allowed .admittance. In this way the remaining 

 nitrogen is consmned, so that, finally, the workirg vessel is 

 charged with a mixture of argon and oxygen only, from which 



