l62 



NATURE 



[Junk 13, 189 = 



(he oxygen is rc-niovcil by urdinary well-know n chemical methods. 

 I may mention that at the close of the 0|Jeration. when the 

 nitrogen is all gone, the arc changes its appearance, and becomes 

 of a brilliant blue colour. 



I have said enough alK)ut this method, and I must now pa-ss 

 on to the alternative method which has been verj- successful in 

 Trof. Kamsay's hands — that c^f abst^ibing nitrogen by means of 

 red-hot magnesium. By the kindness of Prof. Ramsay and Mr. 

 Matthews, his assisUint, we have here the full scaleapparatus before 

 us almost exactly as they use it. On the left there is a reservoir 

 of nitrt>gen derived from air by the simple removal of oxygen. 

 The gas is then dried. Mere it is bubbled through sulphuric acid. 

 It then passes through a long tube made of harcl glass and 

 charged with magnesium in the form of thin turnings. During 

 the |>a.ssage of the gas over the magnesium at a bright red 

 heat, the nitrogen is absorl>ed in a greater degree, and the 

 gas which finally [xisses through is immensely richer in argon 

 than that which first enters the hot tube. At the present 

 time you see a tolerably rapid bubbling on the left, indicative 

 of the flow of atmospheric nitrogen into the combustion 

 furnace ; whereas, on the right, the outflow is very much slower. 

 Care must \k taken to prevent the heat rising to such a point 

 as to soften the glass. I'he concentrated argon is collected in a 

 second gas-holder, and afterwards submitted to further treat- 

 ment. The ap|>aratus employed by Prof. Ramsay in the sub- 

 sequent treatment is exhibited in the diagram, and is very 

 effective for its purjKjse ; but I am afraid that the details of it 

 Would not readily l<c followed from any explanation that I could 

 give in the time at my dlsjxisal. The principle consists in the 

 circulation of the mixture of nitrc^en and argon over hot 

 magnesium, the gas being made to |>a&s round and round until 

 the nitrogen is effectively removed from it. At the end that 

 o|K-ration, as in the case of the oxygen method, proceeds some- 

 what slowly. When the gre;iler part of the nitrogen is gone, 

 the remainder seem> l^i be unwilling to follow, and it requires 

 somewhat protracted treatment in order to be sure that the 1 

 nitrogen has wholly disap|K-arcd. When I say " wholly dis- I 

 appeared," that, |ierha|>s, would be too much to say in any 

 case. What we can say is that the s|)ectrum test is adequate 

 to show the presence, or at any rate to show the addition, of I 

 alfout 1^ ^>er cent, of nitrogen to argon as pure as we can 

 gel it ; .so that it is fair to argue that any nitrogen at that stage j 

 remaining in the argon is only a small fraction of i.J i>er cent. 



I .should have liked at this [Mint to be able to give advice as 

 to which of the two methods — the oxygen method or the 

 magnesium method — is the easier and the more to be recom- 

 ntcnded ; but I confess that I am quite at a lo.ss to do so. One 

 difficulty in the com|>arison arises from the fact that they have 

 lieen in different hands. As far as I can estimate, the quantities 

 of nitn^^en eaten up in a given time are not very different. In 

 that resixrcl, |>erha|is, the magnesium method has some advan- 

 tage ; but, on the other hand, it may be said that the m.agncsium 

 ITT'Kcss retjuires a much closer su|x:rvision, so that, jjerhaps, 

 fourteen hours of the oxygen meth^nl may not unfairly compare 

 with eight hours or .so of the magnesium metho<l. In practice a 

 great deal would dcpenil u|Kin whether in any |>articular labora- 

 tory alternate currents are available from a public supply. If 

 the alternate currents are at hand, I think it may probably be 

 I he case that the oxygen method is the easier; but, otherwise, 

 the inagnesium method woulil, probably, be preferred, esiK'cially 

 by chemi.sts who are familiar with 0|H;rations conducted in red- 

 hot tulxjs. 



I have here another ex|x:rimcnt illustrative of the reaction 

 lictwcen magnesium and nitrogen. Two rods of that metal are 

 suitably mounted in an atniftsjihere of nitrogen, s<j arranged that 

 we can bring them into contact and cause an electric arc to form 

 lictween them. Under the action of the heat of the elecliicarc the 

 nitrogen will combine w ith the nLignesium ; and if we had lime to 

 carrj' out the ex|K'riment we cf>ukl demonstrate a rapiil absftrplion 

 of nitrogen by this method. When the eX|K-riment w.as first tried, I 

 had ho|ied that it might lie |)ossible. by the aid of electricity, to 

 start the action v» effectively that the magnesium would Cfintinueto 

 burn indeiHiidenlly under its own develo|)ed heal in the .atmo- 

 sphere of nitrogen. Possibly, on a larger scale, Mimething of this 

 sort might succce<l, but I bring it forward here tmly as an illustra- 

 tion. \Vc lum on the electric current, and bring the magnesiums 

 together. \'ou ve a brilliant green light, indicating the vapir- 

 isalion of the msigiK-iium. Under the influence of the he.at the 

 magnesium burns, and there is collected in the glass vessel a 

 certain amount of lirownish-lnoking |iowder which consists 



mainly of the nitride of magnesium. Of course, if there is any 

 oxygen present it has the preference, and the ordinary white 

 oxide of magnesium is formed. 



The gas thus isolated is proved to be inert by the very fact of 

 its isolation. It refuses to combine under circumstances in 

 which nitrogen, itself always considered very inert, does 

 combine — both in the case of the oxygen treatment and in the 

 case of the magnesium treatment : and these facts are, [Krhaps, 

 almo.st enough to justify the name which we have suggested for it. 

 But, in itd<iition to this, it has been proved lobe inert uniler a 

 considerable variety of other contlitions such as might have Iteen 

 expected to tempt it into combination. I will not recapitulate 

 all the experiments which have been tried, almost entirol)' 

 by Prof. Isamsiiy, to induce the gas to combine. Hitherto, 

 in our hands, it has not done so ; and I may mention that 

 recently, since the publication of the abstract of our paper read 

 before the Royal Society, argon has been submitted to the action 

 of titanium at a red heat, titanium being a metal having a great 

 affinity for nitrcjgen, and that argon has resisteil the temptatii>n 

 to which nitrogen succumbs. We ne\er have asserted, and we 

 do not now assert, that argon can under no circumstances be got 

 to combine. That would, indeed, be a rash assertion for any 

 one to venture upon ; ami only within the last few weeks there 

 has l>een a most interesting announcement by M. Herthelot, ol 

 Paris, that, under the action of the silent electric discharge, 

 argon can be absorbed when treateil in contact with the vapour 

 of ben/ine. Such a statement, coming from .so great an authority, 

 commands our attention : and if we accept the conclusions, as I 

 sup|X)se we must do, it will follow that argon has, under those 

 circumstances, combined. 



Argon is rather freely soluble in water. That is a thing that 

 troubled us at first in trying to isolate the gas ; because, when 

 one was dealing with very small quantities, it seemed to be 

 always disapjiearing. In trying to accumulate it we made no 

 |)rogress. .\fter a sufficient ijuantity had been iirejiared, special 

 exiwriments were made on the .solubility of argim in water. It 

 has been found that argon, prepared both by the m.-ignesium 

 method and by the oxygen method, has about tile same solubility 

 in water as oxygen -some two-and-a-half tintes the soluliility of 

 nitrogen. This suggests, what has been verified by experiment, 

 that the dissolved ga.ses of water should contain a larger pro- 

 portion of argon than does atmospheric nitrogen. I have 

 liere an apjiaratus <tf a .stuiiewhat rough description, which I 

 have employed in ex|Kriments of this kind. The boiler 

 employed consists of an old oil-can. The water is supplied to it 

 an<l drawn from it by coaxial tubes of metal. The incoming colli 

 water flows through the outer annulus between the twii tubes. 

 The outgoing hot water |wsses through the inner tube, which 

 ends in the interior of the vessel at a higher level. Hy means of 

 this arrangement the heal of the water which has done its work 

 is pas-sed on to the incoming water not yet in operation, and in 

 that way a limited amount of heat is made to bring up to the 

 Imil a very much larger quantity of water than wiiuld otherwise 

 be possible, the greater part of the dissolved ga.ses being liberated 

 at the .same lime. These are collected in the ordinary way. 

 Wh.at you see in this flask is dis.solved air collected tJUt of 

 water in the course of the last three or four hours. .Such gas, 

 when treated as if it were atmospheric nitrogen, that is to say 

 after removal of the oxygen and minor impurities, is lound to be 

 deciilcdly heavier than atmospheric nitrogen to such an extent 

 .as to indicate that the |)ro|«irtit>n of argon contained is almut 

 double. It is obvious, therefore, that the dissolved gases of 

 water form a convenient source of argon, by which some of the 

 lalwiur of separation from air is obviated. During the last few 

 1 weeks I have been supplied from Manchester by .Mr. Macdougall, 

 who has interested himself in this matter, with a quantity of 

 dis.solved gases obtained from the condensing water of his steam 

 engine. 



As to the S|K'Ctruni, we have been inilebted from the fiist to 

 Mr. Crookes, and he has been gi>od enough to-night to bring 

 some lubes which he will o|)erate, and which will show you at 

 all events the light of the electric discharge in argon. I cannot 

 show you the spectrum of argon, for unfortunately the amount of 

 light from a vacuum tulie is not .sufficient for the projection of 

 its spectrum. I'mler .some circumstances the light is red, and 

 under other circumstances it is blue. Of course when these 

 lights are examined with the s|)ectroscope — and they have been 

 examined by Mr. ("rookes with great care the differences in the 

 colour of the light translate themselves into different groups of 

 S|jcclruin lines. We have before us Mr. Crookes" map, .showing 



NO. 1337. vol.. 52] 



