Mr. J. J. Waterston on Chemical Notation. 519 



and that any attempt to put it in a more satisfactory condition 

 deserves the support of chemists. 



When previously remarking on Mr. Odling's statement with 

 reference to sodium, I find that I have understood what he calls 

 hydrate of sodium to be hydrate of soda, and applied the same 

 formulae to it as to the hydrate of potash. Thus Na in contact 

 with HO^, HO^ expels the H of one HO^, and unites with the 

 other HO* *o form the solid hydrate of soda, HO*- NaO*. When 

 this is heated with sodium, the H of the HO* is ejected and gives 

 place to a second Na ; so that HO* . NaO becomes 

 NaO*.NaO*=2NaO*. 



Of hydrate of sodium (if it is not a mistake) I know nothing, 

 nor can I find mention made of it in any work on chemistry that 

 I have access to. If Mr. Odling would have the kindness to 

 express what he means in the V.D. notation, it would then per- 

 haps be possible to understand him. 



With reference to the statement in my previous communica- 

 tion, " that HKO represents one molecule of the hydrate of pot- 

 ash, but HHO not one but two molecules of water, and KKO 

 not one but two molecules of anhydrous potash," Mr. Odling 

 informs us in a note that Mr. Watts (author of the Supplement 

 of Dr. Gregory's f Chemistry ') states to him " that the three for- 

 mulae were meant to express a single molecule each, the three 

 quantities represented being exactly comparable." I repeat that 

 this is impossible, and strikingly shows the inefficiency of Ger- 

 hardt's system when it can so notoriously mislead eminent 

 chemists. The following is the proof: — Let us assume that 

 they do express a single molecule each ; then, since HHO repre- 

 sents a single molecule of water, the value of the symbol H in 

 terms of the weight of a hydrogen gas-molecule considered as 

 unity must be | ; and the value of O must be 8, because the 

 single molecule of water weighs nine times the single molecule 



IT , TT | .r\-\ 



of hydrogen, and is 1 , jl , g r=9. Potassium, K, thrown 

 into water displaces half the hydrogen and forms hydrate of pot- 

 ash, HKO, or i i 39 i g f =47 , 5 ; so that, if the symbols H 



and O retain the same value in the single molecule HHO as in 

 the single molecule HKO, the hydrate of potassa, HKO, must 

 consist of half a gaseous molecule of hydrogen (J), half a gaseous 

 molecule of oxygen (8) and potassium (39). But 39 of potassium 

 in union with 8 of oxygen is potassa, so that all that is left to 

 represent the water of the hydrate is H = J, whereas the water- 

 molecule is HHO. 



