Mixtures of Ethane and Nitrous Oxide. 177 



substances which appear to answer the purpose. Sub- 

 stances of low critical temperatures mostly have high critical 

 pressures and high vapour-pressures. When this is not so, 

 the differences are often too small to promise striking results. 

 My attention was at last drawn to ethane, a substance of low 

 critical pressure ( + 50 atm.) and a critical temperature of 

 + 34°C. Combinations of this substance with HC1, C 2 H 2 , 

 N 2 0, especially the last, promised good results. 



For this combination I expected to find a case such as is 

 represented in fig. 1. It will appear that my expectation has 

 been surpassed in so far as these mixtures happen to offer some 

 interesting properties which had never been observed and 

 require a more complex representation than fig. 1. At the 

 same time the phenomenon (r. c. II.) , to find which was the 

 starting-point of the investigation, has escaped observation 

 till now. 



Preparation of Ethane (C 2 H 6 ). 



8. The ethane was prepared by electrolysis of a concen- 

 trated solution of acetate of sodium. By this process a 

 number of other substances are generated, especially C0 2 , 2 , 

 C 2 H 4 , and some esters*. The gas was washed in sulphuric 

 acid and a solution of caustic soda, and collected in a big 

 glass bottle (45 litres) again containing a solution of caustic 

 soda. In this manner the C0 2 was absorbed entirely. By 

 aid of a mercury compressing machine of Cailletet, which 

 belongs to the set of apparatus of the Leiden Laboratory for 

 experiments at low temperatures, the ethane was liquefied 

 in a small copper vessel. In this operation it passed again 

 through fuming sulphuric acid, caustic potash, and phosphoric 

 anhydride. In order to expel the permanent gases, the liquid 

 ethane was cooled by solid carbonic acid and made to boil. 

 In filling the tubes the gas was afterwards taken from the 

 liquid. 



This method of purification at low temperature has been 

 formerly applied by me to C0 2 and CH 3 Clt. 



Preparation of Nitrous Oxide (X 2 0). 



9. This substance was taken from a commercial bottle ; it 

 was led through high-pressure tubes containing chloride of 

 calcium and caustic potash and afterwards dried over P 2 5 . 

 The purification was conducted as in the former case. During 

 the boiling of the liquid N 2 the tube could be connected 



* Kolbe, Lieb. Ann. lxix. p. 279 ; Wiedemann, Electricitiit, ii. p. 574. 

 t Kuenen, Archives Neerl. xxvi. pp. 356, 359. Olszewski was the first 

 to apply this method of purifying gaseous substances so far as I know. 



