120 Prof. Odling on Chemical Notation. 



chemists — those concerning the ratio of the molecular weights of 

 water and caustic potash for example. 



He affected to teach us that the molecules of the chemical 

 elements are divisible in the act of combination, and that all 

 gaseous molecules, elementary or compound, occupy the same 

 bulk ; the former doctrine satisfactorily established by the re- 

 searches of more than a dozen years ago, and the latter, after a 

 much chequered career, recognized for some time past as a very 

 corner stone of chemical science, notwithstanding that in a Royal 

 Institution lecture to a very general audience I endeavoured to 

 explain it incidentally by what Mr. Waterston complimentary 

 terms " ridiculously clear " illustrations. 



Admitting that all gaseous molecules have the same bulk, the 

 majority of chemists do not think it a matter of much conse- 

 quence how that bulk should be expressed — whether by the ap- 

 position of two semicircles so as to form a single volume 0, as 

 approved by Mr. Waterston, or by the apposition of two entire 

 circles so as to form a double volume 00, as condemned by him, 

 or in any other way. For myself, indeed, I am of opinion, with 

 Laurent and several others, that a single-volume standard is in 

 the abstract preferable, but, not regarding the point as one of 

 any great importance, habitually employ a double-volume stand- 

 ard as affording certain practical advantages which those engaged 

 in chemical practice can probably best appreciate. If Mr. 

 Waterston, however, instead of declaiming against us from his 

 rostrum will show us with civility and, if possible, on a footing 

 of equality, that the point is of more importance than we at 

 present deem it 5 he will assuredly find us well disposed to give 

 his remarks an attentive consideration; but the question not 

 being one with which I am in any special way identified, I must 

 decline to enter into any personal discussion upon it, more parti- 

 cularly with such an antagonist as Mr. Waterston has now proved 

 himself to be ; for how can one discuss chemical questions with a 

 gentleman whose knowledge of the literature and thought of 

 modern chemistry has allowed him to regard the expression 

 " hydrate of sodium " as being either a typographical error or an 

 affected singularity"* ? 



In reply to the query whether " it is possible that the first 

 and most obvious consequence of the equality in bulk of gaseous 

 molecules (namely that the ratios of vapour-densities are also the 

 ratios of molecular weights) is a sealed book in Mr. Odling's 



* Such expressions as hydrate of sodium, nitrate of potassium, sulphate 

 of calcium, &c. are no longer confined to original memoirs or purely che- 

 mical treatises, but are used throughout in such popular works as the Jury 

 Report of the International Exhibition of 1862, Class II. Section A. Che- 

 mical Products and Processes, &c. 



