102 CHEMICAL NOMENCLATURE AND NOTATION. 



much; and a sesqui -sulphate once and a half as much as the 

 neutral sulphate ; while a sub-sulphate contains a less proportion 

 than the neutral salt ; the prefixes referring in all cases to the 

 proportion of acid in the salt, or to the electro-negative ingre- 

 dient^ as in the case of oxides. The excess of base in sub-salts 

 is sometimes indicated by Greek prefixes expressive of quantity, 

 as ^-ehromate of lead, /m-acetate of lead, but this deviation from 

 rule is apt to lead to confusion. If a precise expression for 

 such subsalts were required,, it would be better to say the 

 bibasic subchromate of lead, the tribasic subacetate of lead. But 

 the names of both acid and basic salts are less in accordance 

 with correct views of their constitution,, than the names of any 

 other class of compounds. 



Combinations of water with other oxides are called hydrates, 

 as hydrate of potash, hydrate of boracic acid. 



3. In the names of quarternary compounds or of double 

 salts, the names of the constituent salts are expressed, thus : 

 sulphate of alumina and potash is the compound of the sulphate 

 of alumina with the sulphate of potash ; tartrate of potash and 

 soda, the compound of the tartrate of potash with the tartrate of 

 soda ; the name of the acid being expressed only once, as it is 

 the same in both of the constituent salts. The names alum 

 and Rochelle salt which have been assigned by common usage to 

 the same double salts, are likewise received in scientific language. 

 The chloride of platinum and potassium expresses, in the same 

 way a compound of chloride of platinum with chloride of potas- 

 sium. An oxichloride, such as the oxichloride of mercury ', is a 

 compound of the oxide with the chloride of the same metal. 



The present nomenclature does not furnish precise expres- 

 sions for many new classes of compounds, the existence of 

 which was not contemplated by its inventors, and many of its 

 names express theoretical views of the constitution of bodies 

 which are doubtful, and not admitted by all chemists. But its 

 deficiencies are supplied, and the composition of bodies more 

 accurately represented, in certain written expressions, or chemi- 

 cal formulae, which are also employed to denote particular sub- 

 stances, and which form a valuable supplement to the nomen- 

 clature still generally used. These forrnulee are constructed on 

 the simplest principles, and besides supplying the deficiencies 

 of the old nomenclature, they at once exhibit to the eye the 

 composition of bodies, and afford a mechanical aid in observing 



