THE 



LONDON AND EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[THIRD SERIES.] 



JANUARY 1840. 



Y 



I. On the TJieory of Substitutiojis hi Chemist^, proposed by 

 M. Dumas. In a Letter to M. VqXowzq from M. Berzelius*. 



OU will perhaps permit me to return once more to M. 

 Dumas's theory of substitutions, especially after the 

 new development that this skilful chemist has lately given it, 

 a development which, according to him, threatens to over- 

 turn the theory of chemistry in general, and especially electro- 

 chemical notions. You remember that in a preceding letter, 

 I declared my opinion, that the application which has been 

 made of the theory of substitutions, in considering chlo- 

 rine, which takes the place of hydrogen, as acting the same 

 part as this latter, is contrary to the principles of the science, 

 and I quoted some examples on this subject, which I think 

 prove it in an unequivocal manner. In begging you to com- 

 municate the contents of this letter to the Academie des Sci- 

 ences, I hoped that M. Dumas would have the goodness to 

 explain under what point of view he regards the theory in 

 question. He has, indeed, complied with this request, and in 

 a manner which, with the exception of some details foreign 

 to the question, has entirely satisfied me. 



In the Comptes Rendus of 1838, (l^""^ semestre, p. 699 and 

 the following pages,) M. Dumas has disclaimed this explana- 

 tion of the theory of substitutions : " If I am made to say 

 that chlorine takes the place of hydrogen in such a way that 

 the former acts the same part as hydrogen, an opinion is im- 

 puted to me," says M. Dumas, "against which I protest, for it 

 is opposed to all that I have asserted on these matters. The 

 theory of substitutions merely asserts the simple affinity be- 

 tween hydrogen and the chlorine which takes its place in 

 equal volume. It is an empirical law which deserves our at- 

 tention only as long as it holds good, and if any one has 

 made it of more importance it is not my fault." 



* From the Ann. de Chim. et de Phys., vol. Ixi. p. 137' 



Phil, Mag, S, 3. Vol. 16. No. 100, Jan. 18*0. B 



