1 82 Prof. Odling on Chemical Notation. 



fact, and which is as follows : — He begins by saying that the 

 proper formula for the molecule of water is HO*, and that 

 Gerhard t's formula II HO can only be used at all by letting each 

 H stand for a J part or a half-volume of hydrogen, and O stand 

 for 8 parts or a half-volume of oxygen ; so that in his tempo- 

 rary use of the formula HHO (1 vol.), for the purpose of show- 

 ing a reductio ad absurdum, he halves the usually received values 

 of all the constituent symbols, which halving I am quite ready 

 temporarily to accept. But in reference to Gerhardt's formula 

 for potash, KHO, he halves the usual values of the H and O, 

 making them stand for -J a part and 8 parts of hydrogen and 

 oxygen respectively ; but does not halve the usual value of the 

 K, which he still allows to stand for 39 parts of potassium; and 

 having by this means doubled its actual proportion, exclaims 

 triumphantly that the formula HKO* cannot be correct, 

 because the 39 parts of constituent potassium would require all 

 the 8 parts of constituent oxygen, whereby no oxygen would be 

 left to combine with the J part of hydrogen, — thus intimating, 

 with a recklessness which I forbear to characterize, that the 

 formula for caustic potash deliberately adopted by a large and 

 important section of British and foreign chemists is incompa- 

 tible with the centesimal composition of the body represented — 

 as is also the formula for anhydrous potash, KKO, which is soon 

 afterwards satisfactorily demolished by a similar hocus-pocus, — as 

 if any conjuring with formulae or arguments from notation could 

 decide what is admitted to be a question of fact, or at any rate 

 of interpretation of phenomena. 



It seems that Mr. Waterston, taking his notions of Gerhardt's 

 symbols at second hand, has confounded them with those of 

 Berzelius, with whom O stood for 8 parts (100) of oxygen, H 2 

 or H for 1 part (12*5) of hydrogen, *and K for 39 parts (487*5) 

 of potassium, with which values the composition of caustic 

 potash could not possibly be represented by the formula KHO. 

 But according to Gerhardt, O stands for 16 parts of oxygen, H 

 for 1 part of hydrogen, and K for 39 parts of potassium ; or 

 halving these values to please Mr. Waterston, O will stand for 

 8 parts of oxygen, H for ^ a part of hydrogen, and K for 19'5 

 parts of potassium, which ratio is of course in harmony with the 

 composition of the hydrate. Or adopting Mr. Waterston' s frac- 

 tional formulae, HO£ (1 vol.) will represent the molecule of 

 water, H*Br*0* (1 vol.) the molecule of brominated w T ater or 



* The old formula for caustic potash is KO.HO, or KHO 2 , in which O 

 stands for 8 parts of oxygen. Gerhardt's formula is KH9, in which 9 

 stands for 16 parts of oxygen, so that one 9 having the value 16 is simply 

 substituted for two Os having each the value 8. 



