CHEMICAL NOMENCLATURE AND NOTATION. 105 



Oxalate of peroxide of iron and potash, 



3 (K O, C 2 O 3 ) + Fe 2 O 3 , 3 C 2 O 3 + 6 HO. 



It will be found to conduce to perspicuity, to avoid either con- 

 necting two formulae of different substances not in combina- 

 tion, by the sign plus, or allowing them to be separated merely 

 by a comma, as the plus and comma between symbols or for- 

 mulae are conventionally understood to unite the formulae into 

 one, and to express combination ; and indeed it is advisable to 

 write every complete formula apart, and in a line by itself, if 

 possible. 



The only other circumstance to be attended to in the construc- 

 tion of such formulae is the an angement of the symbols or letters, 

 which is not arbitrary. In naming a binary compound, such 

 as oxide of iron, chloride of potassium, etc. we announce first 

 the oxygen or element most resembling it in the compound, and 

 which is called the electro-negative ingredient ; but in the for- 

 mulae of the same bodies, it is the other or the electro-positive 

 element which is placed first, as in Fe O, and K Cl. In the 

 formulae of salts, it is likewise the electro-positive constituent 

 or the basic oxide which is placed first, and not the acid. 

 Thus the sulphate of potash is K O, S O 3 , and not S O 3 , K O. 

 Information respecting the constitution of a compound may 

 often be expressed in its formula, by attending to this rule. 

 Thus sulphuric acid of specific gravity 1.780, contains two pro- 

 portions of water to one of acid, but by giving to it the follow- 

 ing formula, 



H O, SO 3 + H O, 



we express that one proportion only of water is combined as a 

 base with the acid, and that the second proportion of water, the 

 formula of which follows that of the acid, is in combination 

 with this sulphate of water. 



The .above system of notation is complete, and sufficiently 

 convenient for representing all binary compounds, and com- 

 pounds belonging to the organic department of the science, in 

 the formulae of which the ultimate elements only are expressed. 

 But when salts and double salts are expressed, the formuUe 

 often become inconveniently long. They may often be greatly 

 abbreviated, and made more distinct by expressing each equi- 

 valent of oxygen in an oxide or acid by a dot placed over the 

 symbol of the other element, thus, 



