Manchester Memoirs, Vol. Ixiv. (1920), No. 3 7 



would make clear the two opposing, doubtless very unequal, 

 influences. 



The arrangement of the molecule of formic acid may be 

 said to be heterogeneous from the point of view just elaborated ; 

 acetic acid on the other hand is wholly homogeneous, the sig- 

 nification remaining the same no matter which of the oxygen 

 or hydrogen atoms is imagined to act as " key-atom," 



V 



+H-C-C 



+ 



and the same is true of aceto-acetic acid (Hancke and Koessler, 

 loc. cit.). 



In order to emphasise that aspect of the question of 

 polarities to which he attaches special importance the writer 

 would suggest terming it the " principle of induced alternate 

 polarities." 



It is evident that the rule of MarkownikofT is at once the 

 most natural and elementary outcome of the principle in 

 question, as the addition processes 



XrYi + C = C-X andX^Yj + C = C-Y 



- + - + -- + 



must give rise to 



or, in words, to the accumulation of atoms or groups of like 

 polar character on the same carbon atom. 



It would seem that, in general, the reversible reactions 

 are those which lead to the most homogeneous arrangements, 

 as in the aldol, acetoacetic ester and Raper-MacLean 

 syntheses ; heterogeneous arrangements appear usually to arise 

 as the result of depolarisation effects analogous to oxidation 

 or reduction : but this issue as well as that of variable valency 

 and consideration of amphoteric groups like -CN must for 

 the present be deferred. 



