234 HISTORY OF CHEMISTRY. [LECTURE XII. 



upon the consideration of atomicity and of structural formulae, 

 I shall only need to refer to Kolbe's views, and shall be the 

 better able to point out the influence which he exercised. 



It was not an easy matter for Kolbe to follow Frankland in 

 his most recent developments ; to assume that the affinity of 

 the elements is always satisfied by the same number of atoms 

 without regard to their chemical character amounted to giving 

 up the electro-chemical theory altogether, and to admitting 

 that the electro-chemical nature of the elements was without 

 influence upon the formation of compounds. Kolbe was not, 

 at first, able to reconcile himself to this. 46 In his Text-book, 

 while recognising the premises of Frankland's arguments, he 

 endeavours to combine these with the electro-chemical prin- 

 ciples by means of new hypotheses; 47 and it is only in 1857 



46 Kolbe, Lehrbuch der Chemie 1854, I, 20 et seq. 



47 As evidence for this statement, which Kolbe attacked as erroneous 

 (J. pr. Chem [2] 23, 365), I quote the following passage from Kolbe's 

 Lehrbuch. I, 23 : " Frankland felt himself justified in concluding from 

 this that in cacodyl, stibrnethyl, stannethyl, etc., a real replacement of 

 different oxygen atoms by the same number of atoms of methyl or ethyl 

 takes place ; in other words, that cacodylic acid is arsenic acid which con- 

 tains two atoms of methyl in "place of two atoms of oxygen, and that oxide 

 of stannethyl must be regarded as composed according to the rational formula 



( C* TT 



Sn -! i-v 5 , in which the substitution of one atom of oxygen by one atom of 



ethyl is evident. However little it is possible to agree with this opinion, 

 there can still be no doubt that a regularity does prevail here. The circum- 

 stance is perhaps deserving of attention, that, as is well known, those very 

 elements which stand next after potassium in the electro-chemical series 

 that is, the metals of the alkalies and of the alkaline earths unite with 

 oxygen in but few proportions ; whereas those upon the other side, such as 

 chlorine, sulphur, nitrogen, phosphorus, etc., take up oxygen, on the con- 

 trary, in very numerous proportions. Accordingly, when one of these 

 elements by virtue of its coupling with hydrogen or with ether radicals, 

 approaches more closely to potassium in respect to its electro-chemical 

 character and its affinities, its capacity of now uniting with fewer atoms of 

 oxygen than previously, in consequence of this change of position in the 

 electro-chemical series, may probably be found. less surprising; although it 

 may not by any means be explained how it comes that the number of 

 atoms of the copula and of oxygen is regularly increased up to a definite 

 number," 



