M. Pasteur on the Alcoholic Fermentation of Sugar. 367 



is attacked by potash with extreme difficulty. Heated in the 

 water-bath in a sealed tube with that substance, chloride of po- 

 tassium was formed, and a volatUe chlorine compound, which eva- 

 porated at the warmth of the hand, and burned with a green-edged 

 flame. 



These three chlorides, from their mode of formation, and 

 from the regular gradation of their properties as far as they have 

 been examined, evidently belong to one series. They are iso- 

 meric with the chlorides of the hydrocarbons, C^" H"", but they 

 are not identical ; they differ in the boiling-points and in other 

 properties. Thus chloride of sethylene boils at 82° C, and is 

 readily attacked by alcoholic potash ; the chloride from aldehyde 

 boils at 60° C, and is attacked by potash with extreme difficulty. 

 The difference in boiling-points corresponding to a difference of 

 C^ H^ is 19 degrees in the series of chlorides of sethylene and its 

 homologues, while it is 26 degrees in the series of chlorides from 

 the aldehydes. 



The properties of the body obtained by Geuther, as far as they 

 have been studied, are not very dissimilar to those of Regnault's 

 chlorinated chloride of sethyle. This body boils at 64°, and 

 has the specific gravity 1-24, smells like oil of oletiant gas, and 

 has a sweet but peppery odour. In its deportment towards 

 alcoholic potash it has some of the characteristics of a derivative 

 of aldehyde ; for when treated with that reagent it yields chlo- 

 ride of potassium and a brown sticky resin, while the same odour 

 is perceived which is produced when aldehyde is treated by pot- 

 ash. On the other hand, this substance is not altered by boiling 

 with potassium ; and although the corresponding aldehyde com- 

 pound has not been examined in this respect, its higher homo- 

 logue, chloroenanthole, is decomposed by sodium without very 

 great difficulty. The higher homologues of chlorinated chloride 

 of aithyle are not known ; but the corresponding methyle com- 

 pound, C^ H^ CP,has been described by Regnault, and its boiling- 

 point is 30^. Hence a difference of 34° C. corresponding to 

 a difference of C^ H^. 



It is probable, on the whole, that these three chlorides belong to 

 three different isomeric series — the chlorides of olefiant gas and 

 its homologues, the chlorides from the aldehydes, and the chlo- 

 rinated chlorides of the alcohol radicals. 



Pasteur has observed* that, in the alcoholic fermentation, a 

 portion of tlic sugar becomes changed into succinic acid. When 

 tlic fermented liquid is evaporated and neutralized, and precipi- 

 tated with a silver salt, the precipitate decomposed by sulphur- 



* Comptts Rendus, vol. xlvi, p. 179. 



