February 7, 1895J 



NA TURE 



355 



THE LIOUEFACTIOX AND SOLIDIFICATION 

 OF ARGON.' 



Havint; been furnished, by Prof. Ramsay's kindness, with a 

 sample of the new gas, argon, I have carried out ex^jerime-nts 

 on its behaviour at a low temperature and at hi^h pressures, in 

 order to contribute, at least in part, to the knowledge of the 

 properties of this interesting body. 



Four series of expeiiments in all were carried out, two with 

 the object of d-termining the critical temperature and pressuie 

 of argon, as well as measuring its vapour pressure at several 

 other low temperature'-', while two other series served to dcler- 

 mine its boiling and freezing points under atmospheric pressure, 

 as well as its dm^ity at its boiling point. 



A detailed description of ihe-e experiments will be given in 

 another place ; I sh.ill here give only a short description of the 

 manner in which they were made. 



For the first two expe'iments I made use of a Cailletet's 

 apparatus. Its metallic manoneler had been previously com- 

 pared with the readings of a mercury manometer. As cooling 

 agent I used liquid e'hylene, boiling under diminisheil pressure. 

 The glass tube of Cailletet's apparatus was so arrangecl that the 

 portion immersed in the liquid ethylene had comparatively 

 thin walls {not exceeding i mm.), so as to equalise the external 

 and internal temperature as quickly as possible. 



In both the other experiments the argon was contained in a 

 burette, closed at both end-, with glass stop-cocks. By connect- 

 ing the lower end of the burette with a mercury reservoir, the 

 argon wasiransfeirfd into a narr >w glass lutie fused a: its lower 

 end to the upper end of the burette, and in which the argnn 

 was litjtiefied, and its volume in the liquid state m^a-iured. In 

 these two series of experiments liquid oxygen, bailing under 

 atmospheric or under diminished pressure, was employed as a 

 cooling agent. I made use of a hydrogen thermometer in all 

 these experiments to measure low temperatures. 



Determination of the Critical Constants of Argon. 



As soon as the temperauire of liquid ethylene had been 

 lowered to - I28"'6, the argon ea>ily condensed to a colourless 

 liquid under a pressure of 38 aim tspheres. On slowly raising 

 the temperature of the ethylene, the meniscus of the liquid 

 argon became less and less distinct, and finally vanished. 



Jjeven determinations of the disappearance of the meniscus 

 proved that the critical pressure was 50 6 atmospheres ; but de- 

 terminations of the critical temperature >how slight differences. 



quadruple walls, so as to i-olate the liquid from external heat. 

 Afitr the liquid oxygen had been thus (juured under atmospheric 

 pressure, a great part of it evaporated, fiut there still remained 

 about 70C.C. boiling under atmo-phcnc pressure. A calibrated 

 tube, intended to receive the argon to be liquefie I, and the 

 hydroL^en thermometer were immersed in the boding oxygen. 

 At thi- temperature ( - l82°'7') on admitting argon, no appear- 

 ance of liquefaction could be n iiiced, even when compressed 

 by adding a quarter of an aimosphere pres-ure to that of the 

 atmosphere. This shows ihit iis boiling point lies below that 

 of oxygen. But on diminishirg the temperature of the liquid 

 oxyg n below — 187^, the liquefaction of argon tiecame manifest. 

 When liquef.iciion had taken place, I carefully equalised the 

 pressure of the argon with thai of ihe atmosphere, and regulated 

 the temperature, so that the state of balance was maintained 

 for a long time. This process gives the boiling p lint ol argon 

 under atmospheric pressure. Four experiments gave the 

 numbers - |86°7, - 180° 8, - 187° o, and -iS?'^. The 

 lEean is - i86°'9, which I c >nsider to be the boiling point 

 under atm'tsphenc pressure (740 5 mm.). 



The quantity of ar^ton uscil lor these experiments, reduced 

 to n iimal temperature and pressure, was 99'5 c.c. ; the quan- 

 liiy of liqnid corresponding ttj that volume of t;as was approxi- 

 mately 0'II4 c.c. Hence tlie density of argon at iis boiling 

 point may be taken as approximn ely I '5- Two ether deter- 

 minations of the den-ity ol liquid aigon, for which Iimployed 

 s'lli smaller qiianiities of the gas, yielded rather sm Her numbers. 

 Owing 10 the small amount ol aigim useil for these experiments, 

 I he numbers given cannot lay claim to great exactness; yet 

 they proite that the density of liquid argon at its tioiling point 

 (-187') IS much higher than that of oxygen, which I have 

 found, under similar conditions, to be l*(24. 



By lowering the temjjerature of ihe oxygen to - 191^ by 

 slow exhaustion, the argon froze to a crystalline mass, resem- 

 bling ice; on funher I iwcring temperature it became white 

 and opaque. When the temperature was raised it melted ; 

 four observations which 1 made to determine its melting point 

 gave the num'iers : - 189° o, - igo" 6, - 1S9 6, and - j8y°'4- 

 The mean of these numbers is — 189"'6; ani this may be 

 accepted as the mel'ing point of argon. 



In the following tattle I have given a comparison of physical 

 constants, in which iho-e of argon are compared with those of 

 o h r sj called permanent gases. Tne data are from my 

 previous work on the subject. 



Criik.-il 

 'temperature. 



Critical 

 pressure. 



Boiling 

 point. 



Freezing 

 point. 



Hydrogen (llj) .„ 

 Nitrogen (N„) ... 

 Carbonic oxide (CO) 

 Argon (A,) 

 Oxygen (0„) 

 Nitric oxide (NO) 

 Methane (CHJ 



I 



Freezing 

 pressure. 



60 

 100 



138 



So 



Density 



of gas. 



Densily of 



Liquid at 

 boiling 

 point. 



Colour of 

 liquid. 



The mean of the seven estimations of the crilical lemperniure 

 is — 121 ', and this may be taken as the critical temperature of 

 argon. 



The vapour presi^ures at ten temperatures from — 1286 to 

 I39'i were also determined. 



Determination of the JioiHn:^ and Frazin!^ Points. 



Two hundred cubic centimetres of liquid oxygen, prepared 

 in my large apparatus," was poured into a glass vessel with 



' Abstract of a paper by Dr. K. Olszewski, Professor of Chemisiry in the 

 Vnivcrsily of C<'a'Ow. 



3 BnlUtin international He V Academic dc Cracovic^ June 1890; also 

 Wiedemann's Beibldttcr^ vol. 15, p. ag. 



NO. 1319, VOL. 5 1] 



As can be seen from the foregoing table, argon belongs to 

 the so c.illed " permanent " gases, and, as regards difliculiy in 

 liqnefyirg i', it occupies the founh place, viz. l)rtween carhon 

 m-nnxide and oxygen. lis behaviour on liquefact'on places it 

 nt-are t 10 oxygen, bu' if differN entirely from oxygen in being 

 soIiHifiable : as is well known, oxygen has not yet been made to 

 assume a soli I state. 



The high density of argon rendcrcfl it probable that its 

 liquefaciion would take place at a higher temperature than that 



1 T have re-dciennincd t^^e boiling point nf oxygen, using large quantities 

 of oxvKen. and a hydrogen thermometer of much larecr dimensi'Hs than 

 previously. The registered temperature is i '3 lower th.in that which I pre- 

 viously recorded. 



