_Nomenclature of binary Compounds possessing acid properties._--These are named on a different principle. The termination _ic_ is applied to one element. Thus, taking as an illustration the liquid known as "Oil of Vitriol," it is truly an _Oxide_ of Sulphur, but as it possesses strong acid properties it is termed Sulphur_ic_ Acid. So Nitric Acid is an Oxide of Nitrogen; Carbonic Acid is an Oxide of Carbon, etc. When there are two oxides of the same element, both possessing acid properties, the most important has the termination _ic_, and the other _ous_; as Sulphuric Acid, Sulphur_ous_ Acid; Nitric Acid, Nitr_ous_ Acid. _Nomenclature of the Hydracids._--The Hydrogen Acids are distinguished from Oxyacids by retaining the names of both constituents, the termination _ic_ being annexed as usual. Thus, _Hydro_chloric Acid, or the Chloride of Hydrogen; _Hydr_iodic Acid, or the Iodide of Hydrogen. _Further illustrations of the nomenclature of Binary Compounds._--The Oxides of Nitrogen, and also of Sulphur, afford an interesting illustration of the principles of nomenclature. The former are as follows:-- Nitrogen. Oxygen. Protoxide of Nitrogen 1 atom. 1 atom. Binoxide of Nitrogen 1 " 2 " Nitrous Acid 1 " 3 " Peroxide of Nitrogen 1 " 4 " Nitric Acid 1 " 5 " Observe, that two only out of the five possess acid properties, the others being simple oxides. Nitric Acid is, strictly speaking, the "Peroxide," but as it belongs to the class of acids, that term naturally falls to the compound below. The binary compounds of Sulphur with Oxygen all possess acid properties; they may be represented (in part) as follows:-- Sulphur. Oxygen. Hyposulphurous Acid 2 atoms. 2 atoms. Sulphurous Acid 1 " 2 " Hyposulphuric Acid 2 " 5 " Sulphuric Acid 1 " 3 " In this case the Sulphuric and Sulphurous Acids had become familiarly known before the others, intermediate in composition, were discovered. Hence, to avoid the confusion which would result from changing the nomenclature, the new bodies are termed _Hypo_sulphuric and _Hypo_sulphurous (from ὑπο, _under_). _Nomenclature of Salts._--Salts are named according to the acid they contain; the termination _ic_ being changed into _ate_, and _ous_ into _ite_. Thus, Sulphuric Acid forms Sulph_ates_; Nitric Acid, Nitr_ates_; but Sulphur_ous_ Acid forms Sulph_ites_, and Nitrous Acid, Nitr_ites_. In naming a salt, the base is always placed _after_ the acid, the term _oxide_ being omitted; thus. _Nitrate of Oxide of Silver_ is more shortly known as "Nitrate of Silver," the presence of Oxygen being understood.