io5 



NATURE 



\yzme 2, 1887 



found to work admirably, keeping the whole column in 

 constant agitation and at a measurable temperature. 

 The pressure over the ethylene was maintained by use of 

 the air-pump at about 10 millimetres of mercury. 



By this means such a diminution of temperature was 

 effected that all gases, with the exception of hydrogen, 

 could be liquefied at pressures not exceeding 40 atmo- 

 spheres. As soon as the manometer of the air-pump 

 indicated 10 mm., the valves/and h were closed, and / of 

 the Natterer cylinder opened, admitting the gas to be 

 liquefied into the tube a at 40-60 atmospheres pressure, 

 as indicated by the manometer g, when a considerable 

 quantity of the liquefied gas was readily obtained. And 

 now Olszewski elaborated a most ingenious device, by 

 means of which the liquid could for some time be retained 

 as such on releasing the pressure, and even — which is 

 almost incredible, and a striking example of the truth of 



the adage " fact is stranger than fiction " — in vacuo. 

 The addition to the apparatus consisted of the introduc- 

 tion in the liquefaction tube of a second thinner-walled 

 tube, about half the length of the former and of smaller 

 diameter, so that, when in position, the distance of its 

 walls from those of a was about i millimetre. On per- 

 forming the experiment as before, the Hquid first collected 

 only in this interspace, after a short time also in the 

 inner tube, thus exhibiting two meniscuses ; eventually 

 the hquid in the interspace flowed over into the inner 

 tube, and finally the levels equalized at its edge. The 

 liquid was now gradually freed from pressure by shutting 

 off the Natterer cylinder and its manometer and opening 

 the valve h, and consequently reduced in temperature 

 still further by the evaporation produced, hence the lique- 

 fied ethylene became relatively warmer and caused the 

 liquefied gas contained in the interspace- to evaporate 



entirely away, leaving a badly conducting layer of gas, 

 whose eminent isolating action was found sufficient to 

 keep the remainder in the inner tube in the liquid state 

 at normal atmospheric pressure. One step further : on 

 closing the stopcock 0, and connecting h with s by means 

 of lead and caoutchouc tubing, communication was effected 

 between the liquefaction tube and the air-pump, and, 

 owing to the before-mentioned action of the layer of gas, 

 a notable quantity of the hquefied gas still remained at 

 pressures below 100 millimetres of mercury, as shown by 

 the manometer / The temperature of liquefied oxygen 

 under these circumstances sank to - 198° C, that of air 

 to - 205°, and that of nitrogen to -213°. 



In his latest work Olszewski used two such little 

 isolating tubes, and was enabled to reach in case of 

 oxygen -211°; at -207° and 100 millimetres pressure, 



carbon monoxide solidified, as did also nitrogen at —214 

 and 60 millimetres. 



By lowering the pressure over the solid nitrogen to 4 

 mm., Olszewski succeeded in penetrating the dark region 

 approaching absolute zero as far as —225° C. It will be 

 remembered that Pictet found a pressure of 650 atmo- 

 spheres necessary at —140° to liquefy hydrogen, but by 

 combining the above apparatus with one similar to 

 Cailletet's, so that the gas could be subjected to 190 

 atmospheres pressure at —213°, Olszewski has effected 

 the same result, which was also independently obtained 

 by use of liquefied nitrogen boiling in vacuo (Compt. rend. 

 xcviii. 913, 1884). 



The chief importan:e of these experiments lies in the 

 fact that it now becomes possible to determine several of 

 the physical constants of liquefied gases at ordinary 



