208

NITROGEN-SYMBOL-APPEAL THEREON TO FRANCE.

One conspicuous merit of the elementary symbolization epitomized in this table consists in its Universality; I mean in its general recognition and employment by the chemists of all nations throughout the civilized world.

From this broad statement, however, we have to except one symbol, and one nation. That symbol is the expression N = nitrogen; and that nation is France; for, France alone, among all the nations of the earth, continues to designate nitrogen by the symbol and name Az = azote. It is time that this single deviation from uniformity in the elementary chemical language of the world should disappear; and I confidently appeal to our scientific brethren beyond the Channel to efface this one remaining discrepancy by adopting the symbol N.

It is not necessary, for this purpose, to discontinue the use of the name azote also. The Italians employ the term azoto, but they are beginning to couple with it the symbol N. In the cases of the alkali metals, the French themselves concur with other nations in using the symbols K and Na, though these are not the initial letters of the names (potasse and soude), which they assign to the alkalies. Evidently, therefore, there would be no logical inconsistency involved in this slight concession, on the part of France, to the general usage of the scientific comity of nations. On the contrary, France owes this rectification quite as much to her own genius for philosophical order and unity, as to that general European sentiment whereof, in this appeal, I am but the humble spokesman. Moreover, to a similar, and much more sweeping appeal, on the part of France, scientific Europe has responded with alacrity, by renouncing, in favour of the noble French metrical system, a thousand incongruities of local weight and measure. And again, in the great work of building up, on a unitary basis, the magnificent edifice of modern chemistry, France has taken, in the past as in the present, her fully proportionate share. These are all valid and logical arguments in support of our present plea. When, therefore, we solicit at her hands the abandonment of her one discordant symbol, we do but ask her to carry out the spirit of her own unitary conceptions; and to the successors of Lavoisier to the contemporaries cf Gerhardt-our appeal, we are persuaded, will not be made in vain.

LECTURE XII.

Compounds of a higher order, ternary, quaternary, &c.—laws of proportionality and quantivalential relations exemplified in the generation of such compounds—their frequently high vapour-densities—their tendency, in many cases, to dissociation-examples of ternary compounds-hydrochlorate of ammonia-its production by the union of the molecules of two gaseous binary compounds-its neutral, salt-like characters-dissociation of its vapour-ternary compounds produced during the progressive dehydrogenation of water and ammonia by the alkali-metals—unisodic water, or hydrosodic oxide-unisodic and bisodic ammonias, or hydro-unisodic and hydro-bisodic nitrides-progressive expulsion and replacement of hydrogen-atoms by sodium-atoms during the formation of these compounds-analogous substitution-compound in the marsh-gas group-general conception of substitution-compounds—their production further illustrated in the progressive transformation of water, ammonia, and marsh-gas, by inception of chlorine and expulsion of hydrogen-retention of the structural type of the parent compound by its substitutional derivatives-conversion of binary into ternary compounds by atomic inception, unattended by substitutional displacement-exemplification of this mode of their genesis in the hydrochloroxygen series-analogous ternary compounds of the hydrochloric group-of the water group-hydrosulphoxygen series of the ammonia group-hydrophosphoxygen series-of the marsh-gas group-methylic alcohol-its transitional importance-close of the lecture-summary recapitulation and conclusion of the course. THE principles of symbolization, literal and diagrammatic, illustrated in the table of the elements to which our attention was directed at the close of the last lecture, apply equally to the concise representation of the structure of compound bodies.

Thus, as, in the table, we denote the elementary hydrogen molecule by the letters HH, and depict diagrammatically its diatomic structure by the dilitral figure—

HH

210

COMPOUNDS OF A HIGHER ORDER; THEIR OBEDIENCE

so, likewise, we represent the similarly-formed diatomic compound molecule of hydrochloric acid by the letters HCl, and the dilitral figure—

HCF

Again, as in point of structure and dimensions the polyatomic binary molecules of water-gas, ammonia-gas, and marsh-gas, are all precisely analogous to the elementary diatomic standard molecule, HH, we represent these also, respectively, in the literal expressions HO", HN, and H,C", and by the dilitral doublesquare symbols

When we wish to represent elementary or compound molecules, whose dimensions have not been ascertained by experiment, but are provisionally assumed on analogical grounds, we resort to the dotted lines previously employed by us in like cases; representing, for example, the hypothetical gaseous molecules of the alkali-metals, and their compounds with chlorine and oxygen, as follows:

Though we have hitherto had occasion to employ these methods of symbolization only for the representation of the elements and their binary compounds, they are equally available (mutatis mutandis) to denote the composition and structure of compounds of a higher order; that is to say, of compounds in whose formation not two only, but three, four, five, and sometimes even six elements take part, and which are accordingly distinguished as ternary, quaternary, quinternary, and sexternary compounds.