Intelligence and Miscellaneous Articles. 491 



point of oxygen, of air, of nitrogen, and of carbonic oxide under 

 the ordinary pressure. I obtain all these gases as statical Kquids 

 under the atmospheric pressure in the following way. I lead the 

 gas, which is in a metal receiver already compressed to 100 atmo- 

 spheres, into a glass tube closed at one end and immersed in liquid 

 oxygen. By expanding the oxygen I liquefy the compressed gas. 

 When the expansion is complete, I break the connexion of the 

 tube with the receiver, and bring it slowly in connexion with the 

 atmosphere. The liquefied gas is then under the atmospheric pres- 

 sure, and boils at a temperature corresponding to this pressure. 



Oxygen,- — Perfectly pure oxygen was used for these experiments. 

 It left no crystalline residue at the bottom of the tube. The 

 boiling-point is - 184° C. 



By combining this number with those previously published, we 

 get the whole curve of the liquefaction of oxygen. It is repre- 

 sented by the following table : — 



Temperature. Pressure. Observation. 



atm. 



— 113 50 Critical point. 



-129-6 27-02 



-131*6 25-85 



-133-4 24-40 



-134-8 23-18 



— 135-8 22-2 



-184 ........ 1 



Air.— The boiling-point of air is -192°-2 C. 



Nitrogen obtained from air by copper, as in my former experi- 

 ments on its solidification, boiled at — 193°'l C. It contained 

 possibly traces of oxygen; for, supposing that the boiling-point of 

 a gaseous mixture depends on its composition, we should expect 

 — 194°- 3 C. In any case it is seen that the constituents of air do 

 not separate when they are liquefied. 



Carbonic oxide. — The gas was prepared from oxalic acid, and 

 contained 6 per cent, of carbonic acid. Its boiling-point was 



— 186° C. Assuming that the boiling-point of carbonic acid is 



— 80° C, we have for pure carbonic oxide —193° C, that is the 

 same temperature as for nitrogen. 



Evaporating these gases in vacuo, we sink to some degrees below 

 -200° C. 



As regards hydrogen, which I have only hitherto been able to 

 obtain in the condition of dynamic liquid, I have found a method, 

 which I am about to try, to obtain it as statical liquid, using 

 hydrogen itself as refrigerator. 



It follows from these researches that, of all gases, atmospheric 

 air will be the refrigerator of the future. 



It need not be prepared, and it produces almost the greatest 

 cold. To use it it is compressed to the pressure of liquefaction 

 into metallic receivers. By letting it then pass into other re- 

 ceivers already cooled it will be liquefied, and can then be allowed 



