NA TURR 



T77 



THURSDAY, JANUARY 3, 1878 



THE LAST OF THE GASES 



' I '"HE year 1877 will ever be memorable in the history 

 -»- of scientific progress, its close having been marked 

 by a brilliant series of researches which have ended in an 

 absolute demonstration of the fact that molecular cohesion 

 is a property of all bodies without any exception whatever. 

 This magnificent work divides itself into two stages, 

 which we shall refer to separately : first the liquefaction 

 of oxygen, and then, following close upon this, the 

 liquefaction of hydrogen, nitrogen, and atmospheric air. 



In the liquefaction of oxygen, which we announced last 

 week as having been accomplished by M. Pictet of 

 Geneva, we have not only an instance of the long time 

 we may have to wait, and of the great difficulties which 

 have to be overcome, before a theoretical conclusion is 

 changed into a concrete fact— something definite acquired 

 to science ; but also another instance of a double dis- 

 covery, showing that along all the great lines of thought 

 opened up by modern investigation and modern methods, 

 students of science are marching at least two abreast. 



It appears that as early as December 2 M. Cailletet 

 had succeeded in liquefying oxygen and carbonic oxide at 

 a pressure of 300 atmospheres and at a temperature of 

 — 29° C. This result was not communicated to the 

 Academy at once, but was consigned to a sealed packet 

 on account of M. Cailletet being then a candidate for a 

 seat in the Section of Mineralogy. Hence, then, the 

 question of priority has been raised, but it is certain that 

 in the future the work will be credited to both, on the 

 ground that the researches of each were absolutely inde- 

 pendent, both pursuing the same object, creating methods 

 and instruments of great complexity. We regret, there- 

 fore, that M. Jamin, at the sitting of the Academy to 

 which we have referred, seemed to strain the claims 

 of M. Cailletet by stating that to obtain the gas non- 

 transparent was the same as to obtain it liquefied. We 

 are beginning to know enough of the various states of 

 vapour now not to hazard such an assertion as this. 

 This remark, however, rather anticipates matters, and 

 indeed, as we shall show afterwards, M. Cailletet need 

 not himself be very careful of the question of priority- 

 even if it were ever worth caring for except to keep other 

 people honest. 



Owing to the double discovery and the curious incident 

 to which we have referred, the meeting of the Academy on 

 the 24th ult. was a very lively one, as not only was the 

 sealed packet and a subsequent communication from M. 

 Cailletet read, but M. Pictet had sent a long letter to 

 M. Dumas giving full details of his arrangements. MM. 

 Dumas, H. St. Claire Deville, Jamin, Regnault and 

 Berthelot all took part in the discussion, the former 

 admirably putting the work in its proper place by the 

 following quotation from Lavoisier ;— 



" • • • Considdrons un moment ce qui arriverait aux 

 diff6rentes substances qui composent le globe, si la tem- 

 perature en dtait brusquement changde. Supposons par 

 exemple, que la terre se trouv^t transportde tout k coup 

 dans une legion beauccup plus chaude du systcme solaire 

 dans une rdgion, par exemple, ou la chaleur habituelle 

 Vol. XVII. — No, 427 



serait fort supdrieure k celle de I'eau bouillante ; bient6t 

 1 eau tous les liquides susceptibles de se vaporiser k des 

 degrds voisms de I'eau bouillante, et plusieurs substances 

 metalhques meme, entreraient en expansion et se trans- 

 formeraient en fluides adriformes, qui deviendraient par- 

 ties de l'atmosph6re. 



" Par un efifet contraire, si la terre se trouvait tout k 

 coup placde dans des rdgions tres froides, par exemple de 

 Jupiter et de Saturne, I'eau qui forme aujourd'hui nos 

 fleuves et nos mers, et probablement le plus grand 

 nombre de liquides que nous connaissons, se transforme- 

 raient en montagnes soliies. 



L'air dans cette supposition, ou du moins une partie 

 des substances adriformes qui le composent, cesserait 

 sans doute, d'exister dans I'dtat de fluide invisible, faute 

 d un degrd de chaleur suffisant ; il reviendrait done a I'dtat 

 de liquiditd, et ce changement produirait de nouveaux 

 hquides dont nous n'avons aucune idde." 



When Faraday in the year 1823 (at the age of 31) 

 began the researches indicated in the last paragraph 

 quoted by M. Dumas, and first liquefied chlorine and 

 then several other gases, he had no idea that he had been 

 anticipated, as he had been, by Monge and Clouet, who 

 condensed sulphurous acid before the year 1800, and by 

 Northmore, who liquefied chlorine in 1805. If the great 

 experimenter were among us now how dehghted he would 

 be to see one of the greatest ironmasters of France 

 employing the enormous resources at his disposal at 

 Chatillon-sur- Seine, and a descendant of the Pictet, the 

 firm friend of his great friend De la Rive (who 'was 

 the first to whom he communicated his liquefaction of 

 chlorine), thus engaged in carrying on the work which 

 he made his own. 



The methods employed by MM. Pictet and Cailletet are 

 quite distinct and are theresult of many years' preparatory 

 study, as testified by M. H. St. Claire Deville and M. 

 Regnault. It is difficult to know which to admire most, 

 the scientific perfection of Pictet's method or the wonder- 

 ful simplicity of CaiUetet's. It is quite certain that the 

 one employed by the latter will find frequent use in future 

 experiments. We may briefly refer to both these methods. 

 M. CaiUetet's apparatus has already been briefly 

 alluded to in these columns. It consists essentially of a 

 massive steel cylinder with two openings ; through one 

 hydraulic pressure is communicated. A small tube passes 

 through the other, the sides of which are strong enough 

 to withstand a pressure of several hundred atmospheres, 

 and which can be inclosed in a freezing mixture. It opens 

 within the cylinder into a second smaller cylinder serving 

 as a reservoir for the gas to be compressed. The remain- 

 der of the space in the large cylinder is occupied by 

 mercury. M. CaiUetet's process consists in compressing 

 a gas into the small tube, and then by suddenly placing it 

 m communication with the outer air, producing such a 

 degree of cold by the sudden distention of the confined 

 gas that a large portion of it is condensed, a process 

 perfectly analagous to that used to prepare solid carbonic 

 acid by the rapid evaporation of the liquefied gas. 



In M. CaiUetet's experiment with oxygen it was brought 

 to a temperature of - 29° C. by the employment of sul- 

 phurous acid and a pressure of 300 atmospheres ; the gas 

 was still a gas. But when allowed to expand suddenly, 

 which, according to Poisson's formula, brings it down to 

 200 degrees below its starting-point, a cloud was at once 

 formed. The same result has since been obtained without 



