1872.] 



On the History of the Ethjlene Bases. 



425 



note. If, on the other hand, the sun's meridian producing the maximum 

 varies, the mean period should be sought for each year by the trial of 

 periods of different lengths, as has been done by Dr. Hornstein for Prague, 

 and as I have done for Makerstoun. 



III. "Contributions towards the History of the Ethylene Bases." 

 By A. W. Hofmann, Ph.D., F.E.S., Professor of Chemistry in the 

 University of Berlin. Received May 20, 1872. 



The manufacture of chloral, which, since the discovery of the remarkable 

 physiological properties of this compound, is conducted on a daily increasing 

 scale, gives rise to a variety of secondary products which have not failed to 

 attract the attention of chemists. Some time ago I showed that the 

 most volatile fraction ot these by-products consists almost entirely of 

 chloride of ethyl, constituting a very valuable material for the pre- 

 paration of an abundant quantity of the ethylated ammonias. The fraction 

 boiling between 70° and 100° is chiefly bichloride of ethylene, 

 which, when submitted to the action of alcoholic ammonia at 100°, fur- 

 nishes a supply of ethylene bases such as would be difficult to obtain from 

 other sources. Dr. Schering, one of the principal manufacturers of chloral 

 in Berlin, has lately placed at my disposal between 30 and 40 kilograms 

 of these latter by-products, which the kindness of my friends Drs. Martius 

 and Mendelssohn, by placing at my disposal one of their magnificent 

 enamelled autoclaves, has permitted me to treat in one single operation with 

 alcoholic ammonia. 



The product of this operation was a large proportion of sal-ammoniac 

 deposited in crystals, and a dark alcoholic mother-liquor which, after the 

 alcohol had been distilled off, yielded on evaporation a brown crystalline 

 residue, consisting of salts of ethylene bases. Large quantities of ethylene- 

 diamine chlorhydrate in a state of absolute purity were separated from this 

 mixture by systematic crystallization. An additional portion was procured 

 by distilling the mother-liquor, after it had ceased to crystallize, with an 

 alkali, collecting apart the first products, as long as they yielded with 

 chlorhydric acid the easily crystallizable ethylenediamine salt. In this 

 manner more than a kilogram of the perfectly pure chlorhydrate was ob- 

 tained, not to speak of quantities of the more complex bases, which I have 

 not yet endeavoured to separate. 



A new source of ethylenediamine having thus been opened, I was induced 

 to resume the study of this remarkable substance, the history of which still 

 presents a great number of gaps. I was more particularly anxious to ascer- 

 tain whether some of the reactions, to which the ordinary alcohol bases 

 have of late been found to lend themselves, might be with equal success 

 applied to the ethylene bases. 



1. Action of Carbon Bisulphide on Ethylenediamine. 

 Having repeatedly been engaged during the last few years with the study 



