CHEMICAL NOMENCLA'TIIRE AND NOTATION. (During the progress of the Ency clopsdia, the nomenclature and notation of chemistry were greatly changed. What fol lows here is allowed to stand, as the old names and notation are still found in books in use, and are often used concurrently with the new.) In early times, chemical substances were named according to the .fanciful theories of alchemy (q.v.). Thus the name flowers of sulphur was applied to the sublimed sulphur, which grew or sprang like a flower from sulphur when heated; spirit of salt, to hydrochloric acid, the corrosive acid or spirit obtained from common salt; and a multitude of other names had a like fanciful origin. In 1787, Lavoisier founded the system of nomenclature which is followed still by chemists. At first, it was intended that the names of simple as well as compound substances should be regulated by system. Hence, such terms as oxygen (from oxus, acid, and gennao, to produce), the given from the notion then held that no acid was without oxygen; and hydrogen (from hydor, water, and gennao), the ducer, from the supposition that hydrogen had more to do with the formation of water than any other element. The advance of chemistry, however, has so completely changed the opinion of chemists regarding the simpler bodies, that such names are now found to mislead; and thereafter, though such as had been given on this system were retained, their meaning has been discarded, and the systematized nomenclature restricted to com pound substances. A remnant of the system, however, still subsists at the present time, in making the scientific names of all the metals end in urn. In the non-metallic ele ments, a close analogy exists between chlorine, bromine, iodine, and fluorine; and to indicate this, the common termination ine has been given; and for a similar reason, car bon, silicon, and boron, end in on. As a general rule, however, the chemical name of an elementary substance does not convey any scientific meaning, and must be regarded as a simple mark or designation, analogous to the names of persons, which give no notion regarding their moral character or physical development. The ancient and more common metals retain their popular titles, such as gold, silver, and copper; but the more recently discovered metals have names given which end in urn. The symbol of an 'ele
ment is obtained from the first letter of its Latin name, as 0 for oxygen; Pl. for lead (Lat. plurnbam). When the names of two or more elements commence with the same letter, a smaller letter or satellite is attached to one or more of these; such as S for sul phur, Se for selenium, and Si for silicon. For a complete table of the symbols of the elementary substances, see ATOMIC WEloirrs.
The name of a compound substance generally indicates the elements of which it is composed. Thus the name oxide of iron indicates that the red powder (rust) is made 4 up of oxygen and iron; the sulphuret of lead (galena), that it is composed of sulphur and lead. In all similar combinations— When two elements combine with each other in more than one proportion or equiva lent (see ATOMIC THEORY and ATOMIC WEIGHTS), the names of the compound bodies are contrived so as to express this. The term protoxide is applied to a compound of one equivalent of oxygen with one equivalent of another element; deutoxide to a compound containing a larger proportion of oxygen than the protoxide; and tritoxide when the oxygen is still further increased. The term binoxide is used when oxygen is present in the proportion of two equivalents to one equivalent of the other element; and teroxide when the proportion is as three to one. A suboxide contains less than one equivalent of oxygen; and a peroxide is the highest oxide not possessing acid properties. The same prefixes are applied to the compounds of chlorine, sulphur, etc.
When one element combines with another to produce several compounds possessing acid properties, various terminations are employed to distinguish the compounds. Thus, oxygen combines with a number of the elements to produce with each a series of acid compounds, the more highly oxidized of which receive the termination ic, whilst those containing less oxygen end in ous. Thus, sulphuric acid contains three equivalents of oxygen to one equivalent of sulphur; and sulphurous acid, two equivalents of oxygen with one equivalent of sulphur. These terminations are qualified by the use of the prefixes hypo (under) and hyper (over). Thus, hyposulphurie acid is applied to a com pound containing less oxygen than the sulphuric acid, and hyposulphurous to one with less oxygen than sulphurous acid.