C4 H4 Cl2; C4 { H3Cl } Cl2; C4 { H2Cl2 } Cl2.
Perhaps at a future period, chemical symbols, and especially those of organic bodies, may be made more systematic and more significant than they at present are.
Aphorism XXVII.
In using algebraical symbols as a part of scientific language, violations of algebraical analogy are to be avoided, but may be admitted when necessary.
As we must in scientific language conform to etymology, so must we to algebra; and as we are not to make ourselves the slaves of the former, so also, not to the latter. Hence we reject such crystallographical notation as that of Mohs; and in chemistry we use C2, O3 rather than C2, O3, which signify the square of C and the cube of O. But we may use, as we have said, both the comma and the sign of addition, for chemical combination, for the sake of brevity, though both steps of combination are really addition. 365
Aphorism XXVIII.
In a complex science, which is in a state of transition, capricious and detached derivations of terms are common; but are not satisfactory.
In this remark I have especial reference to Chemistry; in which the discoveries made, especially in organic chemistry, and the difficulty of reducing them to a system, have broken up in several instances the old nomenclature, without its being possible at present to construct a new set of terms systematically connected. Hence it has come to pass that chemists have constructed words in a capricious and detached way: as by taking fragments of words, and the like. I shall give some examples of such derivations, and also of some attempts which have more of a systematic character.
I have mentioned (Aph. XX. [sect. 7]) the word Ellagic (acid), made by inverting the word Galle. Several words have recently been formed by chemists by taking syllables from two or more different words. Thus Chevreul discovered a substance to which he gave the name Ethal, from the first syllables of the words ether and alcohol, because of its analogy to those liquids in point of composition[73]. So Liebig has the word chloral[74].
[73] Turner’s Chemistry, 1834, p. 955