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No. 292. JULY 7, 1865.


On Chemical Nomenclature. By ALEXANDER W. WILLIAMSON, F.R.S., F.C.S.

I HAD some weeks ago the honour of submitting to the consideration of the Chemical Society a few practical suggestions on the subject of chemical nomenclature, framed in the hope of diminishing the inconsistencies which prevail in it at present, and of aiding the development of its best tendencies.

My chief proposal was to adopt, as systematically as possible, terms such as mercurous nitrate, Hg2(NO3)2; mercuric hydronitrate, HgHONO,; hydric sulphate, H2SO; potassic hydrate, KHO; hydropotassic sulphate, HKSO1; hydrodisodic phosphate, HNa,PO,; sodic sulphate, Na2SO; sodic disulphate, Na,S,O,, &c.; ferric oxydisulphate, Fe2O(SO),; ferric dioxysulphate, Fe,O2SO, &c. The result of two evenings' discussion of the subject was to show that the principles of such nomenclature are, upon the whole, approved, and the names formed in accordance with those principles offer altogether greater proportional recommendations than any other names which are before chemists.

In the course of the discussion which took place on the subject, I had occasion to point out that, inasmuch as salts in which the base is hydrogen, such as hydric nitrate, hydric sulphate, hydric phosphate, &c., are admitted to be analogous in their constitution and properties to the salts of the regular metals such as silver, potassium, &c., it is desirable, when describing their reactions, to designate them by names bearing a corresponding analogy to the names of the salts of silver, potassium, &c.; that in describing the reactions of double salts, containing as base partly hydrogen, partly some heavier metal, such as common rhombic phosphate, HNaPO4, it is not only desirable to introduce the name of the hydrogen in a form similar to that of the other metal, but it is really not possible to obtain systematic and consistent names without representing in them the metallic functions of the hydrogen; that when hydrogen is in the place of an acid or chlorous constituent of a salt, it must be described by a term which represents the fact of its having such functions.

In fact it is not allowable to apply to hydrogen-salts names which conceal their analogy with other salts, or which imply the absence of saline constitution in hydrogen salts. Thus it is a faulty expression to say that the common process for preparing so-called nitric acid consists in the action of sulphuric acid on potassic nitrate, forming potassic bisulphate and nitric acid; for such an expression conveys the idea of a mere displacement of VOL. XII. No. 292.—JULY 7, 1865.

one acid by another, whereas the process is admitted to be an interchange of half the hydrogen in hydric sulphate with potassium in potassic nitrate, forming hydropotassic sulphate and hydric nitrate.

It was admitted by all who spoke on the subject at the Chemical Society, that hydrogen-salts must in exact language be named similarly to other salts; and one distinguished member mentioned that, in describing to students such a reaction as the above, he uses such terms as sulphate of hydrogen and nitrate of hydrogen..

It was at first supposed by some members that I advocated the immediate introduction of systematic and accurate names into common and popular language. The learned member felt alarm at the danger of having to speak of mercurous chloride instead of "calomel," manganic peroxide instead of "manganese," hydric sulphate instead of "sulphuric acid," &c.; and manufacturers would certainly not have received with favour a proposal to give up the term "soda " for sodic carbonate, to say arsenious acid instead of "arsenic."

I accordingly hastened to explain that my suggestions towards improving our systematic nomenclature were only expected, if adopted, to react gradually upon the popular language, and that for the present I contemplate acid" as heretofore, meaning those compounds which in ordering a couple of carboys of "sulphuric acid" or "nitric systematic language are designated "hydric sulphate" and "hydric nitrate;" but that when I have to explain to learners the reactions of those hydrogen salts, I should give them the systematic names which correspond to their composition. The popular and trivial names by which they are known are abbreviations formed so as to point to the essential or characteristic constituent. It is not practicable to send out real sulphuric acid, SO,; but manufacturers and consumers know that the value of oil of vitriol is not in the water which it contains, but in the "real acid." In like manner, the common crystals of hydrated sodic carbonate are valuable in proportion to the percentage of soda, Na2O, which they contain, and they are not unreasonably named after their characteristic constituent.

There was, on the part of one or two distinguished members of the Society, a feeling that the retention of of "electro-negative oxides" and "electro-positive oxides" the words acid and base in their established signification might be inconvenient in presence of the fact that chlorine forms with hydrogen a very acid salt, and that some other elements also form acid hydrides. But when it is admitted that H2SO4 is a salt, though of very acid properties, that HNO, and H,PO, are also very acid salts, and that in scientific language they must be designated as salts, it really is not surprising that HCl,HBr, &c., should be salts of considerable acidity, and it is not unnatural to call them salts of hydrogen in systematic nomenclature. The fact that we cannot remove the elements of water from hydric chloride and make Cl2-O, whilst we can remove water from hydric sulphate and make SO-O, is really no reason against classing, side by side, hydrogen salts with compound radicals such as NO, SO, PO, &c., and those with elementary radicals such as Cl, Br. &c.

Since my suggestions have been published, Mr. Foster has published in the Philosophical Magazine a paper "On Chemical Nomenclature, and chiefly on the use of the word Acid." In this paper Mr. Foster expresses assent to the form of names of which I had recommended the systematic adoption; and he says, "If we regard the salts of hydrogen as constituted like the salts of any other metal, the application to them of the

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