We are willing to admit that the subject of electricity is a very difficult one for the chemist to deal with—he must necessarily say much upon it, and is equally obliged to omit abstract details which are often necessary to its explanation, and yet too prolix and bulky for an elementary chemical work. So that it requires considerable acquaintance with the subject to give a perspicuous and yet concise abstract, [p063] such as may be useful to the student. Dr. Turner has not been very successful in effecting this desideratum, and has unnecessarily introduced two sections, the one on electricity, the other on galvanism. He also talks of the “science of galvanism,” which is in bad taste, and erroneously asserts that the energy of the pile is proportional to the degree of chemical action which takes place; a statement by no means correct, inasmuch as the energy of De Luc’s column is directly proportional to the number of alternations, and appears entirely independent of chemical action; and again, a series of 2000 plates, arranged in the usual Voltaic apparatus, when perfectly bright and clean, and the cells filled with distilled water only, give a much more powerful shock, and cause a greater divergence of the leaves of the electrometer than when the apparatus is charged with diluted acids. Here, those very singular phenomena, which electricians distinguish by the terms quantity and intensity, appear perfectly distinct; and between these our author does not sufficiently discriminate, but jumbles the whole under the term activity. In describing the chemical energies, too, of the pile, or its decomposing powers, the Doctor entirely overlooks the important and curious influence of water. He says that acids and salts are all decomposed, without exception, one of their elements appearing at one side of the battery, and the other at its opposite extremity; (i. e. we presume, at its positive and negative poles.) But the fact is, that, excepting where it merely acts as a source of heat, nothing is decomposable by electricity without the intervention of water; the hydrogen and oxygen of which respectively accompany the elements of the other compounds. Not an atom of potassium can be obtained unless the potassa be moistened; nor can any salt be decomposed except water be present. Sir Humphry says, it is required, to render the substance a conductor; but its operation is more recondite, and there is something mysterious and still unexplained in the uniform appearance of hydrogen and oxygen at the opposite poles, when far apart in water, and in all other cases of true polar electro-chemical decomposition. At page 86, the unfortunate protectors of ships’ bottoms are introduced—a subject about which the less is said the better;—and, as to electro-magnetism, it is merely mentioned as to its leading phenomena, in the space of three or four pages; nor is anything new suggested upon the “Theory of the Pile,” as it is called, which concludes the subject, and which is dismissed in the brief limit of a page and a half. [p064]
The second part of Dr. Turner’s work is said to comprise “Inorganic Chemistry,” and therefore embraces a very extensive field of inquiry. To the arrangement we have already objected; and many of the typographical and verbal errors that occur, have been noticed in a contemporary Journal, so that we shall chiefly attend to the details of the sections.
Under the head, “Affinity,” some of the leading facts and doctrines of chemical attraction are perspicuously set forth; but we could have wished that a variety of exploded opinions and erroneous notions had been altogether passed over, as they occupy space which might have been better employed, and can never prove of any other use to the student than to show him the errors and fallacies to which acute philosophers are sometimes liable. Of this kind, especially, are Berthollet’s notions upon the subject of affinity. The doctrine of definite proportion is, on the whole, well and clearly explained; but it would have been much better and clearer, had Dr. Turner confined himself to facts, and meddled less with opinions concerning their cause; he is moreover, in many respects, historically inaccurate. He ascribes much to Dalton that honestly belongs to Higgins;—is much too merciful to Berzelius and his CANONS; and lenient beyond all endurance to the plagiarisms of “Dr. Thomson’s admirable Treatise on the first Principles of Chemistry.”
In the third and following sections, the simple non-metallic substances are described in an order of arrangement which must be very perplexing to the student; otherwise the details are well given, except that here and there the line between theory and fact is not sufficiently marked. Thus we are told that “hydrogen is exactly 16 times lighter than oxygen, and therefore that 100 cubic inches must weigh 33.88816, or 2.118. Its specific gravity is consequently 0.0694, as stated some years ago by Dr. Prout.” Now this is a theoretical deduction, founded upon the specific gravity and constitution of ammonia, (and not upon the composition of water,) and probably correct as applied to pure hydrogen;—but if we weigh the gas, as usually obtained, even with the utmost caution, and of the utmost purity, we shall never procure it so light as here stated, notwithstanding all the learning and argument that our worthy friend, Dr. Thomas Thomson, has issued upon the subject in his various essays in the Annals, and in his magnum opus. We also object to the stress which is often laid upon the whims of individuals, and upon [p065] exploded opinions; instances of which will occur to the reader under the subject of the composition of nitrogen, and the constitution of the atmosphere. We further caution our author against admitting hints, allusions, and inuendos as to the possibility of future inventions and discoveries, as claims upon the merits of such discoveries, when they are actually made. Berzelius has talked a vast deal of nonsense about the composition of nitrogen; and should that discovery ever be made, he will doubtlessly assume the credit of having suggested the steps which led to it. Some foolish persons are apt to think that the Marquis of Worcester was the inventor of Watt’s steam-engine, because he said he had means of raising water by steam, in his Century of Inventions; and we have heard that an eminent chemist of the present day considers himself entitled to all the merit that may belong to Mr. Brunel’s carbonic acid engine, because he had previously stated the possibility of such an application of Mr. Faraday’s important discoveries. The fact is, that these are woeful days for science; all the good feeling and free communication that used to exist among its active cultivators in this country, has given way to petty jealousies and quibbling scandal; one person is exalted for the purpose of depreciating another; and those causes of disgust, which some years ago induced one of our most amiable and able men of science to quit the field, and even leave the country, are becoming daily more prevalent. Were it not an invidious task, we could easily explain and unfold the sources of all this mischief, and shall indeed feel it our duty so to do, should not matters in due time take a more favourable turn; but the task is at once serious and disagreeable, and we therefore postpone it, in the hope of more favourable events. We really believe that, had it not been for the scientific conversationes held during the last season at the houses of a few private gentlemen connected with the learned societies, and more especially the weekly meetings at the Royal Institution, which kept up a friendly intercourse among those who were willing to profit by it, that the whole scientific world would have been at loggerheads, and in that state of anarchy of which the evils may be learned by a short residence at a “northern seat of learning.”
The main object of this digression is to deprecate party in science; and we were led to it by observing, or thinking that we observe, something of such a tendency in the writer whose book is before us—we hope we are mistaken.
The next section comprises “the compounds of the simple [p066] non-metallic acidifiable combustibles with each other.” It includes the important subject of ammonia, of the varieties of carburetted hydrogen, sulphuretted and phosphuretted hydrogen, and cyanogen and its compounds. The metals are then treated of, and to these succeed their salts; and though the execution of this part of the work betrays some haste, it shows also considerable reading, and some originality: the general views are well and clearly sketched, but there are many points upon which we are entirely at variance with our author; and we more especially object to his account of the action of chlorides upon water, and to his notions concerning the “muriates of oxides,” a class of compounds of which, with one or two exceptions, we are disinclined to admit the existence. If common salt be a chloride of sodium, and experiment obliges us so to regard it, what is there in its aqueous solution that should lead us to consider it as containing a muriate of soda; what evidence of any new arrangement of elements? Dr. T. is certainly in mistake, when he says, “for all practical purposes, therefore, the solution of a metallic chloride in water may be viewed as the muriate of an oxide, and on this account I shall always regard it as such in the present treatise.” This inconsiderate dogma taints much of the reasoning upon the chlorides, &c., and is manifestly culled in the Thomsonian school, though we have indeed heard that a Professor at Edinburgh thus addresses his pupils upon the above subject: “The elaborate researches of the illustrious Davy have taught us that common salt is a binary compound of chlorine and sodium, a chloride, therefore, or a chloruret of sodium. But it is only chloride of sodium whilst quiescent in the salt-cellar; for no sooner does it come into contact with the salivary humidity of the fauces, than, by the play of affinities, which I have elsewhere explained, the sodium becomes soda, and the chlorine generates muriatic acid;—that, therefore, which upon the table is chloride of sodium, is muriate of soda in the mouth; and this again, when desiccated or deprived of humidity, retrogrades into its former state.”
Dr. Turner again falls into error, as we humbly conceive, in calling certain salts, such, for instance, as those of the peroxide of iron, sesquisalts, a term properly applied in those cases only where one proportional of a protoxide unites with one and a half of an acid, such for instance as the sesquicarbonate of soda, &c., but in the sesquisulphate of iron, one proportional of the peroxide contains 1.5 of oxygen, and [p067] necessarily, therefore, (according to Berzelius’ canon, if the Doctor pleases,) requires 1.5 of acid to convert it into a salt; just as the commonly constituted peroxides (containing two proportionals of oxygen) require two of acid. Dr. Thomson, with all his nomenclatural pretensions, has fallen into the same error.
The part of our author’s work which treats of the chemistry of organic bodies is, upon the whole, an unexceptionable and accurate epitome of that complicated branch of the science. It has its inaccuracies, but they apparently arise out of the difficulty of condensing into the space of a few pages, matter which, as we have elsewhere remarked, would require an ample volume for its extended and perspicuous details.
In our hasty account of this work, we have rather dwelt upon its defects than its merits, in the hope of seeing another and more extended edition, free from what we consider as serious obstacles to the success and usefulness of the present production. We hope that Dr. Turner will not feel offended at the freedom with which our remarks are offered. We are anxious that a writer of such good information should be induced to think for himself; at least, that he should accurately weigh the pretensions, and inquire into the originality of those views and researches upon which he bestows such unqualified and, in our opinion, undeserved praise, and to which he assents with a facility unbecoming one who evidently possesses the means of testing their merits.