ftonal Institution of (foat Britain. 



WEEKLY EVENING MEETING, 



Friday, January 20, 1899. 



Sir Frederick Bramwell, Bart., D.C.L. LL.D. F.R.S., Honorary 

 Secretary and Vice-President, in the Chair. 



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



Liquid Hydrogen. 



From the year 1878, when the experiments of Cailletet and Pictet 

 were attracting the attention of the scientific world, it became a 

 common habit in text-books to speak of all the permanent gases, 

 without any qualification, as having been liquefied, whereas these ex- 

 perimentalists, by the production of an instantaneous mist in a glass 

 tube of small bore, or a transitory liquid jet in a gas expanding under 

 high compression into air, had only adduced evidence that sooner or 

 later the static liquid form of all the known gases would be attained. 

 Neither Pictet or Cailletet in their experiments ever succeeded in 

 collecting any of the permanent gases in that liquid form for scientific 

 examination. Yet we meet continually in scientific literature with 

 expressions which lead one to believe that they did. For instance, 

 the following extract from the 'Proceedings' of the Royal Society, 

 1878, illustrates this point very well : " This award (Davy Medal) 

 is made to these distinguished men (Cailletet and Pictet) for having 

 independently and contemporaneously liquefied the whole of the 

 gases hitherto called permanent." Many other quotations of the 

 same kind may be made. As a matter of fact six years elapsed, 

 during which active investigation in this department was being 

 prosecuted, before Wroblewski and Olszewski succeeded in obtain- 

 ing oxygen as a static liquid, and to collect liquid hydrogen, which 

 is a much more difficult problem, has taken just twenty years from 

 the date of the Pictet and Cailletet experiments. 



Wroblewski made the first conclusive experiment on the liquefac- 

 tion of hydrogen in January 1884. He found that the gas cooled in 

 a capillary glass tube to the boiling point of oxygen, and expanded 

 quickly from 100 to 1 atmosphere, showed the same appearance of 

 sudden ebullition lasting for a fraction of a second, as Cailletet had 

 seen in his early oxygen experiments. No sooner had the announce- 

 ment been made, than Olszewski confirmed the result by expanding 

 hydrogen from 190 atmospheres, previously cooled to the temperature 

 given by liquid oxygen and nitrogen evaporating under diminished 

 pressure. Olszewski, however, declared in 1881 that he saw colourless 



Vol. XVI. (No. 93.) b 



