Liquefaction of Gases. 209 



action of chlorine and bromine. The action was feeble, but 

 in both cases I obtained products of combination (C 2 H 4 C1 2 

 and C 2 H 4 Br 2 ) in considerable quantity. 



The possibility of preparing relatively large quantities of 

 liquid oxygen in open vessels at atmospheric pressure gave us 

 an opportunity to examine the chemical properties of this 

 interesting substance more closely. We ascertained first the 

 exceedingly feeble chemical affinity of liquid oxygen. A 

 piece of metallic sodium in contact with it showed no change 

 in its metallic brilliancy ; a hardening of the substance, in 

 consequence of its very low temperature, being apparently 

 the only effect produced. This might have been anticipated, 

 considering that every trace of moisture had been frozen 

 away. Potassium acted similarly to sodium. 



But when the reaction of oxidation with light and heat 

 phenomena had already begun, the low temperature ( — 181°*4) 

 is not able to cool the burning substance to such a degree as 

 to interrupt the reaction. For instance, a piece of ignited 

 wood immersed in liquid oxygen takes fire just as in gaseous 

 oxygen ; a steel spring burns and spreads sparks of burning- 

 iron, which in this experiment burst the glass vessel of oxygen, 

 and the liquid oxygen was consequently spilt on the table, 

 giving thus the interesting sight of liquid drops rolling and 

 jumping about in a perfectly spheroidal state. 



In this connexion, as I had (in 1891) large quantities of liquid 

 oxygen, my friend Prof. Kreutz performed a series of expe- 

 riments on the behaviour of coloured substances at very low 

 temperatures, and showed that many of them (HgS, Hgl 2 , 

 I, &c.) become much brighter at — 181°'4. 



From this summary of researches, as well as of dates, it 

 follows that the first apparatus serving to produce large 

 quantities of the liquefied so-called permanent gases, with the 

 solitary exception of hydrogen, was constructed by me. This 

 apparatus can be enlarged at will by increasing its parts, but 

 without changing anything in its construction, so that it 

 might be used to obtain liquefied gases in factories should 

 they at any time prove of practical utility. By means of 

 this apparatus I obtained as large quantities of liquid gases 

 as I wanted ; and they were used for the first time on a large 

 scale as cooling agents (for instance, in my attempts to liquefy 

 hydrogen), or as an object of scientific researches (the 

 absorption spectrum of liquefied oxygen, its coefficient of 

 refraction, &c.) 



The experiments of Prof. Dewar are merely the repetition 

 Phil Mag. S. 5. Vol. 39. No. 237. Feb. 1895. P 



