NA TURE 



JO> 



THURSDAY, FEBRUARY 7, 1895. 



ARGON. 



THE scene in the theatre of the University of London 

 on Thursday last was in many respects unique. 

 It will certainly be historical. It was unique in that the 

 Royal Society had formally invited members of two 

 other scientific bodies to attend the meeting, and had 

 left the comparative seclusion of Burlington House 

 to meet, in Builington Gardens, an audience numbering 

 at least eight hundred. It was the first of a series of 

 discussion meetings to which, we suppose, similar invi- 

 tations will be issued ; but it will be long before the same 

 eagerness to obtain a ticket is displayed — long before 

 those who gain admission, will listen to so much worth 

 hearing. 



The previous history of the subject to be " discussed " 

 is known to most of our readers. Lord Rayleigh has 

 for some years been engaged on one of the most difficult 

 of physical measurements, namely, the determination of 

 the densities of some of the more permanent gases. In 

 the case of nitrogen, he was confronted with the fact 

 that if obtained from chemical compounds, it was about 

 one half per cent, lighter than if extracted from the 

 atmosphere. This result he published in the spring of 

 last year, and the cause of the discrepancy was a subject 

 of general conversation in scientific circles. Lord Ray- 

 leigh himself discussed it with some of his chemical 

 friends. Prof. Ramsay was interested, and since last 

 Thursday he has confided to an interviewer some details 

 as to the part he played in solving the problem. It 

 appears that he asked Lord Rayleigh's permission to 

 investigate the matter, that using a chemical method he 

 I succeeded in separating a heavier constituent from 

 I atmospheric nitrogen, and that on writing to Lord Ray- 

 leigh, he learned that he, too, had achieved, the same 

 result by a process of ''sparking." 



The fact of the discovery was announced in a semi- 

 public way at the meeting of the British Association at 

 ' Oxford. Of course it attracted great attention, and 

 curiosity was further stimulated by the silence of the dis- 

 coverers during the five succeeding months. Towards 

 j the end of last year it was announced that they would 

 give their results to the world in January. On Thursday 

 last the promise was fulfilled, and all that is known of 

 " Argon " was told to all. 



Three papers were read, which showed that the period 

 of silence had been devoted to strenuous work. It was 

 proved beyond possibility of doubt or question that the 

 atmosphere contains a hitherto unknown constituent. It 

 has been separated from the air by atmulysis, by red-hot 

 magnesium, and by " sparking," Its density has been 

 determined to be about 197. It is very soluble in water, 

 and it has been proved that the nitrogen extracted from 

 rain-water is twice as rich in argon as that which exists 

 in the air. 



Mr. Crookes has found that the new substance has 

 two spectra, marked by red and blue lines respectively. 

 Both he and Prof. Schuster certify that the principal lines 

 are identical in the case of two specimens obtained by 

 different methods. The properties at very low tempera- 

 NO. 1319, VOL. 51] 



tures have been determined by Prof. K. Olsrewski, of 

 Cracow. The critical temperature is - 121° C, the critical 

 pressure 506 atmospheres. The liquid boils under a pres- 

 sure of 740-5m.m. at - 186--9, having at the boiling 

 point a density of about 1-5. The melting point is about 

 — 189" 6, and it has been frozen into a white solid 

 resembling ice. Last, but not least, the ratio of the 

 specific heats of the gas is approximately i 66, and all 

 attempts to induce it to enter into chemical combination 

 with other substances have up to the present entirely 

 failed. 



After this torrent of well-established facts, it cannot 

 reasonably be doubted that Lord Rayleigh and Prof. 

 Ramsay have really discovered a substance, which, 

 though existing in enormous quantity, has hitherto 

 defied detection. Lord Rayleigh's work first showed 

 that there was something to explain ; the patience and 

 masterly skill which he displayed throughout years 

 devoted to weary weighings, must command universal 

 admiration. As has been well said, the result is " the 

 triumph of the last place of decimals," that is, of work 

 done so well that the worker knew that he could not be 

 wrong. Prof. Ramsay, too, is to be congratulated in that 

 when this preliminary stage had been accomplished, his 

 energy and skill enabled him to take such a share in the 

 hunt after the unknown cause of the difficulty, that he 

 rightly ranks as a co-discoverer of the new gas. 



In scientific invisstigations, however, the answer to 

 one question always suggests others, and interest in a 

 discovery quickly precipitates into interest in its results. 

 Seldom have a series of facts and figuies raised more ' 

 important issues. The ratio of the specific heats is I •66, 

 which points to the conclusion that the substance is 

 monatomic. If it is monatomic, it must be an element 

 or a mi.\ture of elements. If it is a single element, its 

 atomic weight must be about 40, and m that case no 

 place is ready for it in Mendeldefi''s table. The easiest 

 way out of the difficulty is to suppose that argon is a 

 mixture, and the authors point out that there is evidence 

 for and against this view ; " for, owing to Mr. Crookes 

 observations of the dual character of its spectrum ; 

 against, because of Prof. Olszewski's statement that it 

 has a definite melting point, a definite boilmg point, and 

 a definite critical temperature and pressure ; and because 

 on compressing the gas in presence of its liquid, pressure 

 remains sensibly constant until all gas has condensed to 

 liquid. The latter experiments are the well-known 

 criteria of a pure substance, the former is not known 

 with certainty to be characteristic of a mixture." The 

 question is to be further investigated, but at present the 

 authors conclude that the balance of evidence is in 

 favour of simplicity. 



On this hypothesis a very awkward question is no 

 doubt raised. The periodic classification of the elements 

 cannot, and ought not, to be abandoned at the first 

 challenge, and till further evidence is forthcoming a 

 heavy strain is thrown on the link of the chain of argu- 

 ment which connects the ratio of the specific heats with 

 the monalomicity of the gas. 



On the other hand, the conclusion that if the ratio of 

 the specific heats is 166 the gas can be diatomic, is 

 directly contrary to all .analogy. Merely to say that 

 mercury is monatomic, that Kundt found that the 



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