System of Chemical Notation. 131 



bols are prime to one another. If we put this in place of the 

 author's fundamental hypothesis and adopt all the rest of his 

 reasoning, we shall arrive at a notation substantially the same as 

 that which we now use. 



This will be most distinctly seen by examining, first, those 

 symbols in the determination of which the question of the divi- 

 sibility of the hydrogen unit does not arise ; and secondly, those 

 in which it does. 



Of the first kind we have the symbols of oxygen, sulphur, se- 

 lenium, mercury, carbon, silicon, tin, zinc, and cadmium. 



Of the second, we have hydrogen, chlorine, iodine, bromine, 

 nitrogen, phosphorus, arsenic, boron, antimony, and bismuth. 

 Silver, according to one hypothesis, belongs to the one set, and 

 according to another, to the other. 



In the first set we have uniformly 



= 2. f, S = 2.0, Se = 2.A, Hg = 2.S, C = 2.k, 



Si = 2.<r, Sn = 2./c, Zn = 2.?, Cd = 2.* 2 . 



That is, there is only a difference of unit, but no difference of re- 

 lative value. So far for the atoms or " prime factors." When we 

 turn to the molecules or " units" we find the same thing. Oxygen, 

 sulphur, and selenium are f 2 , # 2 , and A, 2 , just as we have O 2 , S 2 , 

 and Se 2 ; while zinc and cadmium are £ and K q , as we have Zn 

 and Cd. The units of carbon, silicon, and tin are undetermined, 

 and so are their molecules. In all of these cases the author has 

 proceeded on the assumption that each element contains one 

 peculiar prime factor not to be found in any other element; and 

 as his fundamental hypothesis, the indivisibility of the hydrogen 

 unit, does not affect his reasoning, he does not assume that they 

 contain any other prime factor. His assumption is therefore 

 here the same as ours ; and his reasoning would have been the 

 very same as it is, as far as the determination of the units and 

 prime factors is concerned, had he taken hydrogen as a n , n being 

 any number whatever. 



It is quite different wben we come to the second class of ele- 

 ments. Taking chlorine as an instance, we have the equation, 

 (unit of hydrogen) (unit of chlorine) = (unit of hydrochloric acid) 2 . 

 The first term of the equation must therefore be a square. This 

 can only be the case (1) if (unit of hydrogen) and (unit of chlo- 

 rine) be both squares, which is contrary to the author's assump- 

 tion, — or (2) if (unit of chlorine) be a product of an odd power 

 of (unit of hydrogen) and another factor which is a square ; and 

 this is contrary to the common assumption. Here, therefore, we 

 part company : we adopt the simplest form of the first hypothesis 

 and make (unit of hydrogen) = H 2 , and (unit of chlorine) = CI 2 ; 



K2 



