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XL VII. On the Application of the Vapour- density system of No- 

 tation to express Chemical Reactions. By J. J. Waterston, 

 Esq. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



IN the following communication I give an example of the ap- 

 plication of the vapour-density system of notation to express 

 chemical reactions ; and to place it in comparison along side of 

 Gerhardt's system, I have selected the formulae from M. Wurtz's 

 memoir on the glycols (Ann. de Chim. vol. lv.), where that system 

 is applied with great distinctness, and accompanied with vapour- 

 density measurements. It appears from a passage in M. Wurtz's 

 lecture on the Oxide of Ethylene, delivered before the London 

 Chemical Society, June 5, 1862, that he considers Gerhardt's 

 system as only provisional. * * * " car les barres qui ne sont 

 point superflues dans ce moment de confusion, ne sont que provi- 

 soires et devront disparaitre par la suite " (Ann. de Chim. Nov. 

 1863, p. 361). 



1 have appended some remarks on the so-called hydrates of 

 metals of the new school of chemists, as one of M. Wurtz's ex- 

 periments has the appearance of favouring their views, but is, 

 in my opinion, rather an example of the liability of being led 

 astray by defective symbolism — defective because founded on 

 substitutional rather than on physical characteristics. 



P. 402 (Ann. de Chim. vol. lv.) . " Supposons qu'on ait fait 

 reagir sur 1 equivalent de bromure d' ethylene G 2 H 4 Br 2 , par 

 exemple, 2 equivalents d'acetate d'argent, il se formera par 

 double decomposition du bromure d'argent et du glycol diace- 

 tique. Dans cette reaction, ces 2 equivalents de brome se sont 

 portes sur les 2 equivalents d'argent, et le radical G 2 H 4 , se sub- 

 stituant a ces 2 equivalents d'argent dans les 2 molecules d'ace- 

 tate d'argent, relie Fun a Fautre les restes de ces molecules de 

 maniere a former la nouvelle combinaison. On a, en effet, 



G 2 H 3 Ag O 2 \ p 2 TT4 -D..2 __ J"G 2 H 3 p 2 tj4^ 2 1 i o a o. Br • 

 G 2 H 3 Ag0 2 J + " \G 2 H 3 ^ U 02j*+<^d-B 1 > 



2 equivalents Brom. Glycol 

 d'acet. d'arg. d'ethyl. diacetique. 



2 ^H3oj G+G2H4Bi , = < rc : H :0)2 | 02+3AgBr ,, 



Phil. Mag. S. 4. Vol. 27. No. 182. April 1864. T 



