412 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



was very caustic to the skin and its vapour was irritating and 

 suffocating even in small doses ; it was a strong acid, but 

 had none of the bleaching properties of chlorine. Its 

 chemical properties were almost identical with those of 

 acetic acid, from which it differed only in the replacement 

 of hydrogen by chlorine ; using modern formulae, 



C 2 H 4 2 + 3 C1 2 = C 2 HC1 3 2 + 3 HC1. 



Dumas prepared and analysed its silver, ammonium and 

 potassium salts, and its methyl and ethyl ethers, and showed 

 that these were similar in type to the corresponding deriv- 

 atives of acetic acid, and that the composition of each could 

 be predicted from the simple theory of substitution. A 

 similar fixity of type was observed in the conversion of 

 aldehyde 1 into chloral 



C 2 H 4 + 3 C1 2 = C 2 HC1 3 + 3 HC1, 

 in Malaguti's chlorination of ether 



C 4 H 10 + 4 C1 2 = C 4 H 6 C1 4 + 4 HC1, 



and in Regnault's conversion of ethylene into chloroethylene 

 or vinyl chloride (Ann. de Ctiimie, 1855, 58, 301-320) 



C 2 H 4 -HC1 2 = C 2 H 3 C1 + HC1. 

 Dumas sums up these observations as follows : 



" Acetic acid, aldehyde, ether, olefiant gas, losing hydrogen 

 and taking an equal volume of chlorine, produce substances 

 belonging to the same type as themselves, chloracetic acid, 

 chloraldehyde, chlorether and chlorolefiant gas." 



" In all these substances, chlorine, taking the place of 

 hydrogen, did not change the properties of the compound at 

 all, whether it was acid, base or neutral substance, for it 

 remained acid, neutral substance or base, and even retained 

 exactly its power of saturation ". . . . 



" From the conversion of acetic acid into chloracetic acid, 

 from that of aldehyde into chloraldehyde, from the fact that 



1 Prepared by Liebig as an oxidation- product of alcohol, C 2 H 6 O 4- 

 O = C 2 H 4 O + H 2 O, and described by him as aldehyde, abbreviated from 

 alcohol dehydrogenatns (Ann. Chirn. Phys., 1835, 59> 2 9) 



