4S4 



NATURE 



[September 12, 1S95 



two investigators then combining their labours, followed up the 

 subject, and have given us a iDemoir which will go down to 

 I«sterily among the greatest achievements of an age renowned 

 for its scientific actiWty. 



The case in favour of argon being an element seems to be now 

 settled by the discover)' that the molecule of the gas is mon- 

 atomic, as well as by the distinctness of its electric spark 

 sp--ctrum. The suggestion put forward soon after the discovery 

 was announced, that the gas was an oxide of nitrogen, must 

 have been made in complete ignorance of the methods by which 

 it was prepared. The possibility of its being Nj has been con- 

 sidered by the discoverers and rejected on very good grounds. 

 Moreover, Peratoner and Oddo have been recently making some 

 experiments in the laborator)' of the University of Palermo with 

 the object of examining the products of the electrolysis of 

 hydrazoic acid and its .salts. They obtained only ordinary 

 nitrogen, not argon, and have come to the conclusion that the 

 anhydride N3.X3 is incapable of existence, and that no allotropic 

 form of nitrogen is given off. It has been urged that the 

 physical evidence in support of the monatomic nature of the 

 argon molecule, viz. the ratio of the specific heats, is capable of 

 another interpretation — that argon is in fact an element of such 

 extraordinar)' energy that its atoms cannot be separated, but are 

 b<3und together as a rigid system which transmits the vibrational 

 energy of a •^und-wave as motion of translation only. If this 

 b: the state of aflTairs we must look to the physici.^ts for more 

 light. So far as chemistry is concerned, this conception intro- 

 duces an entirely new set of ideas, and rai.ses the question of the 

 monatomic character of the mercury molecule which is in the 

 same category with respect to the physical evidence. It seems 

 unreasonable to invoke a special power of atomic linkage to ex- 

 plain the monatomic character of argon, and to refuse such a 

 power in the case of other monatomic molecules, like mercury or 

 cadmium The chemical inertne.ss of argon has been referred 

 also to this same power of self-combmation of its atoms. If this 

 explanation be adopted it carries with it the admission that thosie 

 elements of which the atoms composing the molecule arc the 

 more easily dissociated should be the more chemically active. 

 The reverse appears to be the case if we bear in mind X'ictor 

 Meyer's researches on the di.ssociation of the halogens, which 

 prove that under the influence of heat the least active element, 

 iodine, is the most easily dissociated. On the whole, the 

 attempts to make out that argon is polyatomic by such forced 

 hypotheses cannot at present be considered to have been suc- 

 cessful, and the contention of the discoverers that its molecule is 

 monatomic must be accepted as established. 



In .searching for a natural source of combined argon Prof 

 Ramsay was led to examine the ga.ses contained in certain 

 uranium and other minerals, and by steps which are now well 

 known he has been able to isolate helium, a gas which was dis- 

 covered by means of the spectroscope in the solar chromospliere 

 iluring the eclipse of 1868 by Profs. Norman Lockyer and E. 

 Krankland. In his address to the British As.sociation in 1872 

 {A'eporls, 1S72, p. Ixxiv.) the late Dr. \V. B. Carpenter said : — 



" But when Krankland and Lockyer, seeing in the spectrum 

 of the yellow solar prominences a certain bright line not identi- 

 fiable with that of any known terrestrial flame, attrituile this to 

 a hypothetical new substance which they propose to call helium, 

 it is obvious Ih-it their assumption rests on a far less secure 

 foundation, until it shall have received that verification which, 

 in the ca.sc of Mr Crofikes' researches on thallium, was afforded 

 by the actual discover)- of the new metal, whose presence had 

 l>een indicated to him by a line in the spectrum not attributable 

 to any sul>stance then known." 



It must be as gratifying to Profs. Lockyer and Krankland as 

 it is to the chemical world at large to know th.it helium may now 

 l>c removed from the category of solar myths and enrolled among 

 the elements of terrestrial matter. The sources, mode of i.sola- 

 lion, and properties of this gas have l>een descrll>e<l in the 

 (lapcrs recently puVilished by Prof. Ramsay and his colleagues. 

 Not the least interesting fact is the r>ccurrence of helium and 

 argon in meteoric iron from Virginia, as announced by I'rof. 

 Ramsay in July {Nature, vol. lii. p. 324). Like argon, 

 helium is monatomic and chemically inert so far as the present 

 evidence goes. The conditions under which this element 

 exists in clcvcite, uraninite, and the other minerals have yet to 

 lie fictermincd. 



Taking a general survey of the results thus far obtained, it 

 seems that two representatives of a new group of monatomic 

 elements characterised Ijy chemical inertness have been brought 



NO. 1350, VOL. 52] 



to light. Their inertness obviously interposes great difficulties 

 in the way of their further study from the chemical side ; the 

 future development of our knowledge of these elements may be 

 looked for from the physicist and spectroscopist. Prof. Ramsay 

 has not yet succeeded in effecting a combination between argon 

 or helium and any of the other chemical elements. M. Moissan 

 finds that fluorine is without action on argon. M. Berthelot 

 claims to have brought about a combination of argon with 

 carbon disulphiiie and mercury, and with *' the elements of ben- 

 zene, . . . with the help of mercury," under the influence of 

 the silent electric discharge. Some experiments which I made 

 last spring with Mr. R. J. Strutt with argon and moist acetylene 

 submitted to the electric discharge, both silent and disruptive, 

 gave very little hope of a combination Iwtween argon and carbon 

 being possible by this means. The coincidence of the helium 

 yellow line with the Dj line of the solar chromosphere has been 

 challenged, but the recent accurate measurements of the wave- 

 length of the chromospheric line by Prof. (i. E. Hale, and of 

 the line of terrestrial helium by Mr. Crookes, leave no doubt as 

 to their identity. Both the solar and terrestrial lines have 

 now been shown to be double. The isolation of helium has not 

 only furnished another link proving community of matter, and, 

 by inference, of origin between the earth and sun, but an exten- 

 sion of the work by Prof Norman Lockyer, M. Deslandres, and 

 Mr. Crookes, has resulted in the most interesting discovery that 

 a large number of the lines in the chromospheric spectrum, as 

 well as in certain stellar siiectra, which had up to the present 

 time found no counterparts in the spectra of terrestrial elements, 

 can now be accounted for by the spectra of gases contained with 

 helium in these rare minerals. The question now confronts us, 

 .■\re these gases members of the .same monatomic inert group as 

 argon and helium ? Whether, and by what mechanism, a 

 monatomic gas can give a complicateti spectrum is a jihysical 

 question of supreme interest to chemists, and I ho(W that a dis- 

 cussion of this subject with our colleagues of Section A will be 

 held during the present meeting. That mercury is capable 

 under different conditions of giving a series of highly complex 

 spectra can be seen from the memoir by J. M. Eder and K. 

 \'alenta, presented to the Imperial .'\cademy of Sciences of 

 \'ienna in July 1894. With respect to the position of argon and 

 helium in the ]wriodic system of chemical elements, it is, as 

 Prof. I\ams.ay points out, premature to speculate until we are 

 quite sure that these gases are homogeneous. It is possible that 

 they may be mixtures of monatomic g-ases, and in fact the spec- 

 troscope has already given an indication that they contain some 

 constituent in common. The question whether these gases are 

 mixtures or not presses for an immediate answer. I will venture 

 to suggest that an attack should be made by the method of dif- 

 fusion. If argon or helium were allowed to ditVuse fractionally 

 through a long porous plug into an exhausted vessel there might 

 be some separation into gases of difl'erent densities, and showing 

 modifications in their spectra, on the assumption that we arc 

 dealing with mixtures composed of molecules of different 

 weights. 



NOTES. 



The Times of Tuesday List contained a letter, signed by Profs. 

 M. Koster, E. Ray Lankester, and G. B. Howes (lion. Secre- 

 taries to the Provisional Committee), with reference to the 

 General Committee now being formed for the purpose of 

 establishing a memorial of the late Prof Huxley. The letter 

 states that 1 1. R.I I. the Prince of Wales has been pleased to 

 become the Honorary President of the Committee. No very 

 active steps can be taken until after the autumn recess, when 

 the General Committee will hold its first meeting, probably in 

 October. The Honorary Secretaries will after that rep<irt the 

 progress that has been made both in this country and abro,id, 

 and a list of the complete Committee and a statement of the 

 subscriptions received will be published. Appended to the 

 letter is a list of an enormous number of names of persons who 

 have already signified their desire to serve on the Committee. 



A MKMORiAi. tablet in lumour of Prof. Helnihollz has been 

 aflixed to the house, No. 8 Ila<litzstrassc, at Potsdam, where he 

 was born, and it is staled that it is intended to erect a joint 



