Mr. W. Odling on Chemical Notation. 



381 



Col. I. 

 H 2 . . , 



CP. ,- . 



. Hydrogen . . 

 . Chlorine . . 



Col. II. 

 . . H 



. CI 



O 2 . . 



HCl . , 



. Oxygen . . . 

 . Muriatic acid . , 



, . 

 • H*C1* 



H 2 . , 

 H 3 N . 



. Water . . . 

 . Ammonia . . 



. HO* 

 . . H H N* 



H 4 C . 



. Marsh-gas . . 



. . H 2 ^ 



H 6 C 2 



. Alcohol . . . 



. . H 3 CO* 



H 10 C 4 



. . Ether . . . 



. . H 5 C 2 0* 



HNO 3 



. . Nitric acid . . 



. . H^N^O 11 



Now, if all the above formulae be halved, as Mr. Waterston sug- 

 gests, but not newly suggests, or if they be doubled, or trebled, 

 or quadrupled, they will still all of them represent one and the 

 same bulk of gas, which may still be considered as 1, 2, 3, 4, or 

 100 volumes. 



At present a large section of chemists, more especially of 

 foreign chemists, who use the comparable formulae given in 

 column I., select a quadruple volume for their molecular unit, 

 while a majority, I believe, prefer for various reasons to look 

 upon the bulk expressed by each of the above formulae as corre- 

 sponding to two volumes, or they take a double volume for 

 their molecular unit ; but both parties are perfectly aware that 

 these are mere matters of convention, and that each formula 

 might equally well be considered to represent one volume only. 



For myself, however, I fully admit that the relative advantages 

 of a 1-volume and a 2-volume unit, as discussed by Mr. Water- 

 ston, and the best mode of constructing a 1-volume notation, 

 whether by integral or fractional formulae, are topics which, 

 though not by any means novel, are well worthy of serious con- 

 sideration on their own bases — that is to say, quite irrespective of 

 my lecture, which had nothing whatever to do with them. 



But Mr. Waterston's impression, that what are known as Ger- 

 hardt's formulae must necessarily be halved, and consequently 

 fractional, as shown in column II., in order to correspond re- 

 spectively with one gaseous volume, is altogether opposed to the 

 long-established general understanding, and, I would add, though 

 I have no wish to discuss the point, is not, in my opinion, well 

 founded. 



Thus on page 83 of Laurent's posthumous Methode de Chimie, 

 published so long ago as 1 854, and, I think, in some of his earlier 

 memoirs, it is distinctly stated that Gerhardt's formulae may be 

 taken to represent one volume only. He says, " La notation par 



