354 Dr. L. Bleekrode. On the Determination of the 



12. Ammonia (H 3 N). 



I prepared this gas in its liquid condition in the most convenient 

 way by filling a tube with strongly dried granulated calcium chloride ; 

 whilst a current of pure ammonia gas was passing through it for some 

 time, the gas became copiously absorbed, and the filled tube served 

 afterwards, by means of a moderate heat, to deliver a large quantity 

 of gas in the glass cell, connected with the tube, which by its own 

 compression became liquid. 



The experiments gave D=15 - 78 millims., and with the natrium 

 light d=3'87 millims., n=l'325 at the temperature of 16'5, and with 

 daylight n= 1*331 at 16*5. I turned my attention to some amine 

 compounds, which are in chemical properties similar to ammonia, and 

 are prepared from it by substitution. 



Among them only mcthylamine requires liquefaction, as it boils at 

 4, and the liquefaction is easily effected by means of a freezing 

 mixture, which is also desirable, when working with dimethylamine 

 and trimethylamine, having boiling points respectively at 9 and 

 9'3. I ordered these compounds from the renowned chemical 

 workshops of Kahlbaum at Berlin, whence I received them in sealed 

 glass tubes, and they were distilled in proper bent tubes connected as 

 usual with the parallel-sided glass cells. 



I obtained with the natrium light 



M. Temp. 



Methylamine, CH 5 N 1 '342 .... 17 '5 



Dimethylamine, C 2 HN 1 '350 17 



Trimethylamine, C 3 H 9 N . . 1 '353 16 



The determination of the index for other amines presents no 

 peculiar interest, as their boiling point is high enough to admit the 

 ordinary methods of observation. 



13. Ethylene (C 2 H 4 ). 



The history of the liquefaction of this gas is somewhat curious. It 

 was already liquefied in 1845 by Faraday on application of both in- 

 creased pressure and low temperatures (42 atmospheres at 1), but 

 as the notion of critical temperature was then not fully understood, it 

 remained unobserved for this gas, though it is very easily obtained. 

 In 1880 Amagat* published an experimental verification of Boyle's 

 law for this gas, and my compatriot, Professor v. d. Waals of 

 Amsterdam, deduced on theoretical grounds from the results 

 obtained the critical temperature of liquid ethylene, and had it 



* Amagat, " Sur la Compressibilite dee Gas sous Fortes Pressions," " CompUs 

 Kendus," 1880, t. 91. 



