LIQUID HYDROGEN.' 



By Professor Dkwar, M. A., LL. D., F. R. S., M. R. I. 



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

 were attracting- tlio attention of the scientific world, it became a com- 

 mon habit in text-books to speak of all the permanent gases, without 

 any qualification, as having- been liquefied; whereas these experimen- 

 talists, 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 li(i[uid form of all the known gases would be attained. Neither 

 Pictet nor Cailletet in their experiments ever succeeded in collecting 

 au}^ of the permanent gases in that liquid form for scientific examina- 

 tion. 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 

 li(juelied the whole of the gases hitherto called permanent." 



Man}" 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 l)eing prosecuted, before Wroblewski and Olszewski 

 succeeded in obtaining 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 liquefaction 

 of hydrogen in January, 1881. He found that the gas, cooled in a 

 capillary glass tube to the boiling point of oxygen and expanded 

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

 sudden el)ullition, 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 



' Read at meeting of the Royal Institution of Great Britain, Friday, January 20, 

 1899. Reprinted from Proceedings of the Institution. 



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