GENERAL REMARKS REGARDIXG ELEMENTS. 61 



twenty years. These changes were made in conformity with 

 our present or modern views of the. constitution of compounds, 

 but many years may yet pass before a uniform system of nomen- 

 clature will be generally adopted. 



When two elements combine in one proportion only, little 

 difficulty is experienced in the formation of a name, as, for in- 

 stance, in iodide of potassium or potassium iodide, KI, chloride 

 of sodium or sodium chloride, NaCl. 



When two elements combine in more than one proportion, 

 the syllables mono, di, tri, tetra, and penta are frequently used 

 to designate the relative quantity of the elements. For instance : 

 Carbon monoxide, CO, carbon dioxide, C0 2 , phosphorus tri- 

 chloride, PC1 3 , phosphorus pentachloride, PC1 5 . 



In many cases the syllables ous and ic are used to distinguish 

 the proportions in which two elements combine; the syllable 

 ous being used for the simpler or lower, the syllable ic for the 

 more complex or higher form of combination. For instance: 

 Phosphorous chloride, PC1 3 , and phosphoric chloride, PC1 5 ; 

 ferrows oxide, FeO, feme oxide, Fe 2 3 . 



The syllables mono and sesqui are also occasionally used to 

 mark this difference, as, for instance, monoxide of iron, FeO, 

 sesquioxide- of iron, Fe 2 3 . 



When two oxides of the same element ending in ous and ic 

 form acids (by entering in combination with water), the same 

 syllables are used to distinguish these acids. Phosphorous 

 oxide, P 2 3 , forms phosphorous acid; phosphonc oxide, P 2 5 , 

 forms phosphoric acid. 



The salts formed by these acids are distinguished by using 

 the syllables ite and ate. Phosphite of sodium is derived from 

 phosphorous acid, phosphate of sodium from phosphoric acid. 

 Sulphas and sulphates are derived from sulphurous and sul- 

 phuric acid, respectively. 



According to the new nomenclature, the name of the metal 

 precedes that of the acid or acid radical in an acid. For in- 

 stance, sodic phosphite or sodium phosphite, instead of phos- 

 phite of sodium; potassic sulphate or potassium sulphate, in- 

 stead of sulphate of potassium. The acids themselves are 

 looked upon as hydrogen salts, and are named accordingly: 

 hydrogen nitrate for nitric acid, hydrogen chloride for hydro- 

 chloric acid, etc. 



