192 Prof. C. Olszewski on the 



meter, based on the alteration of the electric conductivity of 

 a thin iron wire, has been constructed by Prof. Witkowski *, 

 my fellow-worker on the optic properties of liquid oxygen. 



Liquefaction of Large Quantities of Oxygen and Air. 



[Description of the apparatus given in the Bulletin International de 

 VAcademie des Sciences de Cracovie, June 1890, under the title, " K. 

 Olszewski, Trans vasement de l'Oxygene liquide."] 



Though I have simplified and improved my former appa- 

 ratus for liquefying gases to such a degree that I have been 

 able to show the liquefaction of oxygen to a numerous 

 auditory during the lecture, yet it leaves much to be desired 

 as regards the practical application of liquefied gases as cooling- 

 agents. 



By means of my former apparatus I was able to obtain 

 only small quantities of liquefied gases ; a greater diameter 

 could not be given to the glass tubes used for the purpose, 

 because they would not resist the high pressure which 

 is necessary for liquefaction. Besides this, the use of glass 

 tubes exposed to high pressures is always attended with some 

 danger : it often happens that tubes tested for 60 atm. some- 

 times burst during the experiment at 40 atm., or even at a 

 lower pressure. 



I proved long ago (6) that liquid oxygen is the best cooling 

 agent ; for it easily gives the temperature of — 211 c *5 C. if 

 the pressure is lowered to 9 millim. of mercury, and it does 

 not freeze even at the pressure of 4 millim. 



To obtain considerably larger quantities of liquid oxygen 

 for the purpose of applying it as a frigorific agent, it was 

 necessary, instead of brittle glass, to use a substance endowed 

 with more resisting-power, even though not transparent, and 

 to find means to pour the liquid oxygen into a glass vessel. 

 My new apparatus excludes the inconveniences of the former 

 one, and renders it possible to preserve the liquid oxygen a 

 longer time under the ordinary atmospheric pressure. 



A flask of wrought iron, 5 litres in capacity (such as is used 

 to hold liquid carbon dioxide), containing oxygen under a 

 pressure of 80 atm., is joined by a narrow copper tube to the 

 upper end of a steel cylinder tested at a pressure of 200 atm. 

 This cylinder, having a capacity of 30-100 cub. centim., 

 according to the quantity of oxygen which we wish to liquefy 

 at a time, is immersed in liquid ethylene, of which the tem- 

 perature may easily be lowered to —140° C. by means of an 



* Bull. Intern, of the Acad, of Cracow, May 1891, p. 188. 



