CHEMICAL NOMENCLATURE AND NOTATION. 1 01 



Another class of acids exists in which sulphur is united with 

 the other element in the place of oxygen. The acids thus 

 formed are called sulphur-acids. The names of the correspond- 

 ing oxygen acids are sometimes applied to these, with the 

 prefix sulpho, as sulpho-arsenious and sulpho-arsenic acids, which 

 resemble arsenious and arsenic acids respectively in composition, 

 but contain sulphur instead of oxygen. Lastly, certain sub- 

 stances, such as chlorine, sulphur and cyanogen, form acids 

 with hydrogen, which are called hydrogen acids, or hydracids. 

 In these acid compounds the names of both constituents appear 

 as in the terms hydrochloric acid, hydrosulphuric acid, and hydro- 

 cyanic acid. Thenard has lately altered these names to chlor- 

 hydric, sulphohydric and cyanhydric acids, which are certainly 

 preferable terms. 



2. Compounds of the second order, or salts, are named 

 according to the acid they contain, the termination ic of the 

 acid being changed into ate, and ous into ite. Thus a salt of 

 sulphuric acid is a sulphate ; of sulphurous acid, a sulphite ; of 

 hyposulphurous acid, a hyposulphite ; of hyposulphuric acid, a 

 hyposulphate ; and of hyperchloric acid, a hyperchlorate / and the 

 name of the oxide indicates the species, as the sulphate of the 

 oxide of silver, or the sulphate of silver, for the oxide of the 

 metal being always understood it is unnecessary to express it, 

 unless when more than one oxide of the same metal combines 

 with acids, as sulphate of the protoxide of iron, and sulphate of 

 the peroxide of iron. These salts are sometimes called proto- 

 sulphate and persulphate of iron, where the prefixes proto and 

 per refer to the degree of oxidation of the iron. The two 

 oxides of iron are named ferrous oxide arid ferric oxide by 

 Berzelius, and the salts referred to, the ferrous sulphate, and 

 the ferric sulphate. The names stannous sulphate and stannic 

 sulphate express in the same way, the sulphate of the protoxide 

 of tin, and the sulphate of the peroxide of tin. But such 

 names, although truly systematic and replacing very cumbrous 

 expressions, involve too great a change in chemical nomencla- 

 ture to be speedily adopted. Having found its way into com- 

 mon language, chemical nomenclature can no longer be altered 

 materially without great inconvenience. It must be learned as 

 a language, and not be viewed and treated as the expression of 

 a system. A super-sulphate contains a greater proportion ol 

 acid than the sulphate or neutral sulphate j a /v^-sulphate twice us 



