254 Mr. J. J. Waterston on Chemical Notation in 



as the only system mathematically conformable to the law of 

 volumes) is as follows : — Potassium, K, in contact with water, 

 HOi HO% HO*, &c, expels the H of one HO* and unites with 

 another HO^ forming the solid KO* HO*. Another K heated 

 with this solid expels the H and takes the 0* of the HO*, the 

 result being KO*, KO*. The first is a double act of combina- 

 tion, forming one molecule out of three. The second is a case 

 of resolution by preponderating affinity. 



With reference to chloride of potassium : when potassa, 

 KO*HO*, or KO* is presented to H*C1*, H*C1* in water, the 

 0^ in one molecule of the oxide unites with the two H* of two 

 molecules of the acid to form water (no hydrogen is evolved), and 

 the two CI* of the same two molecules of acid unite with the K, 

 forming KC1, the chloride of potassium. 



C1*H* 

 Potassium in hydrochloric acid gas, K, l A , releases two 



H* of two molecules of the acid to form H (which is evolved), and 

 the two CI* unite with K to form KC1. Lastly, potassium, K, 

 in chlorine, CI, takes fire and burns into KC1. 



After discussing several cases of substitution and of chemical 

 parallels as arguments adduced "to show that the molecular 

 weight of water is 18, corresponding to the formula H 2 ,; , and 

 not 9, corresponding to the formula HO', Mr. Odling makes the 

 following remark : — " In addition to the above-mentioned che- 

 mical parallel, there is one very remarkable physical relation 

 subsisting between marsh-gas, ammonia, water, and hydrochloric 

 acid, namely that all four molecules occupy the same bulk. Two 

 cubic feet, for instance, of hydrochloric acid gas, HC1, yield one 

 cubic foot of hydrogen and one cubic foot of chlorine. Two 

 cubic feet of steam, H 2 O, yield two cubic feet of hydrogen and 

 one cubic foot of oxygen, &c." The meaning is apparently that 

 the symbols attached to the letters express the number of volumes 

 of the constituent gases in two volumes of the compounds. That 

 this should be noticed as " a very remarkable physical relation " 

 at once indicates that the mode of notation, although it is founded 

 on the law of volumes, is nevertheless defective. All molecules, 

 simple or compound, in the gaseous state, occupy the same 

 bulk. This the dynamic theory proclaims as a fact. Let the 

 notation be founded thereupon, and we obtain, expressed with 

 perfect conciseness, at once the chemical composition, the phy- 

 sical density of a unit volume, and the constitution of a molecule. 

 The analytical chemist may object to the introduction of fractional 

 exponents, from the preconceived notion that a gaseous molecule 

 is with more propriety to be viewed as a combination of two or 



