1896.] New Besearches on Liquid Air. 133 



WEEKLY EVENING MEETING, 



Friday, March 27, 1896. 



Edward Frankland, Esq. D.C.L. LL.D. F.R.S. Vice-President, 

 in tlie Chair. 



Professor Dewar, M.A. LL.D. F.E.S. M.B.L 



New Besearches on Liquid Air. 



Op all the forms of engineering plant used in low temperature 

 research, the best and most economical for the production of liquid 

 air or oxygen is one based on the general plan of the apparatus used 

 by Pictet in his celebrated experiments on the liquefaction of oxygen 

 in the year 1878. Instead of using Pictet's combined circuits of 

 liquid sulphur dioxide and carbon dioxide, maintained in continuous 

 circulation by means of compression, liquefaction and subsequent 

 evaporation, it is preferable to select ethylene (after Cailletet and 

 Wroblewski) for one circuit, and lor the other either nitrous oxide 

 or, better, carbon dioxide. Further, instead of making highly com- 

 pressed oxygen to be liquefied by heating potassium chlorate in an 

 iron bomb directly connected with the refiigerator, it is safer and 

 more convenient to use gas previously compressed in steel cylinders. 

 The stopcock that Pictet employed to draw off liquid and produce 

 sudden expansion, was in his apparatus placed outside the refriger- 

 ator proper, but it is now placed inside, so as to be kept cool by the 

 gases undergoing expansion. This improvement was introduced along 

 with that of isolating the liquid gases by surrounding them with their 

 own cooled vapour in the apparatus made wholly of copper, described 

 and figured in the Prcc. Koy. Inst, for 1886. In all continuously 

 working circuits of liquid gases used in refrigerating apparatus, the 

 regenerative principle applied to cold, first introduced by Siemens in 

 1857, and subsequently employed in the freezing machines of Kirk, 

 Coleman, Solvay, Linde and others, has been adopted. Quite inde- 

 pendently, Professor Kamerlingh Onnes, of Leiden, has used the re- 

 generative principle in the construction of the cooling circuits in his 

 cryogenic laboratory.* Apart, therefore, from important mechanical 

 details, and the conduct of the general working, nothing new has 

 been added by any investigator to the principles involved in the con- 

 struction and use of low temperature apparatus since the year 1878. 



♦ See paper by Dr. H. Kamerlingh Onnes, on the " Cryogenic Laboratory 

 at Leiden, and on the Production of very low Temperatures," Amsterdam 

 Akademie, 189i. 



