CHAPTER XX. EXPERIMENTAL PHILOSOPHY, INCLUDING CHEMISTRY, ELECTRICITY, MAGNETISM, &c. THE rapid changes that have taken place in the experimental sciences, the increased precision and labour of modern investigation, and the numerous facilities that are afforded by the institution of philosophical societies, and the publication of their transactions, have greatly diminished the number of separate works on the subjects of chemistry, magnetism, electricity, and the like. The whole life of an individual would scarcely suffice to fill a very few volumes with the details of accurate and original experiments, the greater part therefore of the important accessions to this branch of knowledge has been already mentioned in Chapter XVIII. In the present, the most laborious work, Doctor Thomson's System of Chemistry, though upon the whole praise-worthy, and in many parts highly meritorious, has not earned the reputation of uniform and equal excellence. Mr. Chenevix's Remarks on Chemical Nomenclature, bear strong indications of that candour, good sense, discriminating accuracy, and ingenuous modesty, which are the constant characteristics of this eminent and rising philosopher. And Dr. Skrimshire's Chemical Essays exhibit in a pleasing and popular manner, the application of chemistry to the various uses and conveniences of human society. ART. I. A System of Chemistry. By THOMAS THOMSON, M.D. Lecturer on Che mistry in Edinburgh. 8vo. 4 Vols. A WORK on chemistry which aspires to so high a rank as the present publication, which professes to give "a full detail of the vast number of facts which constitute this important science, blended with the history of their gradual development, and of the theories which have been founded on them, and accompanied with exact references to the original works, in which the different discoveries have been registered," claims for itself the most respectful attention. Having had some experience ourselves of the labour that must be gone through, and the judgment that is required in consulting a multiplicity of authors, in discriminating truth from falsehood, in reconciling apparent contradictions, even when a single difficulty occurs, we were, we confess, surprised that any one man, however intense may have been his application, and however great may be his sagacity, should venture to undertake a full detail of the facts and history of, perhaps, the most comprehensive division in the whole circle of science. Neither was our surprise diminished, when we found that four moderate sized octavo volumes, was the whole space allotted by the author to this vast design, including besides, a system of mineralogy, and a considerable number of articles on animal and vegetable physiology. Having been much prepossessed in its favour, we have perused the book with considerable attention, and with every possible disposition to be entirely satisfied. We should, however, be negligent of our duty to the public, if we were to profess that our expectations have been wholly fulfilled. For our own sake, for the author's sake, and from a regard to our readers, instead of dictating a few general sentences of blame or praise, we shall, as far as is consistent with our limits, enter into an analysis of the volumes before us, an attention which their merit well deserves, and which, perhaps, may be of service to a future edition. The first of the three books into which the first part of the work is divided, treats of simple substances, and first of all of oxygen; but as it is an essential part of Dr. Thomson's plan not to mention any compound till he has described all the elements of which it consists, we here meet with little else than the usual methods of procuring this gas, its physical properties, and its capability of supporting flame and animal life. The second chapter is devoted to the consideration of five simple combustibles, viz. sulphur, phosphorus, carbon, hydrogen, and azot. Besides the physical properties of sul phur, the combinations of this substance with oxygen in different proportions are mentioned, and we are introduced, somewhat prematurely, to the Stahlian theory of the composition of sulphur, and its refutation by Lavoisier. Phosphorus is treated of on the same general plan, and its combination with sulphur, as investigated by Pelletier, is also mentioned. The combustibility of the diamond is described under carbon, and the component parts of carbonic acid and charcoal are affectedly and improperly stated to be diamond and oxygen, Lavoisier's term carbon, is by no means a "mere useless synonym," for it is a matter of serious importance to keep the terms of mineralogy as distinct as possible from those of chemistry. The third chapter is devoted to the metals, their physical properties, alloys, and combinations with the preceding substances, but is by no means satisfactory; there are several errors, and still more omissions, from not consulting the German chemists. In the introductory section, Mr. T. says, that the oxyd of lead is reducible per se, by heating in close vessels, which is a mistake. The action of caustic potash on platina, is not noticed either here or under potash, though it is a fact sufficiently notorious to all practical chemists, having been mentioned first by Klaproth, five or six years ago. The possibility of sulphuret of platina is denied, though Proust expressly describes this compound. Of the alloy of gold and platina, there is a very meagre account, from Dr. T's not being acquainted with Vauquelin's ANN. Rav. VOL. I. admirable experiments on this important mixture: they may be found in his Manul de l'Essayeur. Putty is described as a simple oxyd of tin, which it never is, the tin being always combined for the sake of more easy oxydation with a large proportion of lead. Instead of the proper method of preparing aurum musi vurn, we are only presented with a reference to Pelletier. No notice is taken of Newton's fusible metal, composed of tin, lead, and bismuth. The general remarks with which this chapter is concluded, are very trifling, and shew that the author has pursued this part of his subject rather in his study than his laboratory. The assertion that most of the metallic sulphurets are destitute of metallic lustre, is a singular oversight, and can only be attributed to haste or inattention. With more satisfaction we turn to chapters four and five, which treat of light and caloric. These are upon the whole very well drawn up: the arrange. ment is clear, the proportion assigned to the several sections is judicious, no important facts are omitted, difficulties are advanced with candour, and a sober spirit of doubt befitting the intricacy of the subject is very properly inculcated. The second book relates to compound bodies, which are divided into primary and secondary. In the former of these divisions we were somewhat surprised at finding the alkalies and earths, apparently for no other reason than because one of these thirteen substances, ammonia, has been decomposed. Dr. T. was under no sort of necessity to adopt the absurd distinction of simple and compound bodies, as the essential principle of his arrangement; but having done so, it was incumbent on him to adhere to it. In wanton deviation, however, from his own plan, we find fifteen simple sub stances, viz. two alkalies, ten earths, and three acids, placed among the com pounds. The account of the alkalies, though brief, is satisfactory. With regard to the earths, we remark a want of minute accuracy, that is extremely inconsistent with the promise made in the preface of a "full detail of facts." The methods of obtaining alumine and silex, as mentioned here, are not the most accurate; and Agustine, which rests upon the sole and insufficient authority of Trommsdorf, ought to have been omitted. 3 M The oxyds of carbon, of hydrogen (or water), and azot, are next described, and the controversy concerning the decomposition of water is ably and fully stated; the oxyds of azot, however, would be more in place under nitrous acid. The second volume commences with the acids. Their properties are described with general exactness, but by no means with that attention to minute circumstances, which is so peculiarly valuable to the practical chemist. Thus in the preparation of nitric acid, no notice is taken of the use of nitrat of barytes and nitrat of silver, in purifying it from the sulphuric and muriatic acids with which it is always contaminated. The method of forming oxalic acid from sugar is transcribed from Bergman, but the most œconomical preparation of it from galls, is omitted. The preparation of gallic acid, according to Scheele's method, is not truly reported. To the acids succeed the compound combustibles, including the fixed and volatile, oils, alcohol and ether; the account of the latter of which articles is drawn up with great care, and is highly satisfactory. The secondary compounds are introduced by a description of the combinations of earths, both natural and artificial: one section of the chapter is on the manufacture of earthenware, and shows that the author never visited a pottery in his life; the processes are described from imagination, and are almost entirely erroneous, as well as miserably defective. To this succeeds a chapter of half a dozen pages on glass, in which the interesting experiments of Reaumur and Lewis are totally omitted; and, incredible as it may appear, not a single word is mentioned of the indispensible use of manganese, in rendering flint glass colourless. The salts with earthy, alkaline, and metallic bases, are next treated of, but in our opinion not sufficiently at length, considering their vast importance; of this the articles borax and tartar are striking examples. After the salts come the hydrosulphurets, which are briefly described, and the division of secondary compounds is terminated by a chapter on soaps. This contains some good matter from Pelletier, but betrays a want of acquaintance with the practices of our own manufacturers. The class of acid soaps, though improperly so named, ought not to have been left out. Starkey's soap too, and the rest of the savonules, had a claim to notice, which was by no means invalidated by the few words said about them, under essential oils. Having thus gone through the various chemical substances, Dr. T. proceeds to investigate the philosophy of chemistry, in a long chapter on affinity. In the perusal of this we have been particularly pleased, nor shall we by petty objections attempt to detract from its great merit. The second part of this work is entitled a Chemical Examination of Nature, and is divided into five books. The first book treats of the atmos phere, its chemical composition, and the science of meteorology. The second book relates to waters, both common and mineral, and their analysis. These subjects are largely and well treated, but are for the most part by no means essential to a system of chemistry. The third book treats of minerals, and is executed as well as can be expected from a person who is obviously ac quainted with them only through the medium of books, and who, from being a stranger to the German language, labours under additional disadvantages. To one only beginning to study mineralogy, this abstract will be wholly unintelligible, and the practised mineralogist will despise it. At the end of this book is a chapter on the method of analysing minerals, which we are sorry to say is by no means correct. The last section of it, containing the methods of obtaining the metals in a state of purity, is faulty in almost every article. For example: and precipitated by sulphat of soda, wash the "Lead may be dissolved in nitric acid precipitate, and melt it in a crucible, with two and a half times its weight of black flux." Now it is obvious that this process will not separate lead from arsenic, bismuth, silver, or antimony, and the lead, instead of being in the metallic state, will be a sulphuret. Book IV. is concerning vegetables, and contains three chapters. The first relates to the vegetable principles, and is both defective and incorrect; of which the section relating to resins, is a most flagrant instance. The second and longest chapter treats of vegetation, and contains much physiological matter, which has nothing to do in a system of chemistry. The third chapter, in the short compass of twenty-three pages, affects to give an account of the manufactures of bread, wine, beer, and vinegar, together with vegetable putrefac tion. The fifth book treats of animal substances; first concerning the animal principles; secondly, concerning the animal solids and fluids; thirdly, concerning the chemical changes that take place in digestion, respiration, the secretion of urine, perspiration, and assimilation; fourthly, on the decomposition of animal bodies. This book is much more laboured and satisfactory than the preceding; proper use has been made of the investigations of Fourcroy and Vauquelin, and the other modern inquirers into this intricate but interesting subject. The analysis of urine, milk, and blood, and the section on respiration, do credit to the author as a medical chemist. Our opinion of Dr. Thomson's work may readily be inferred from the short abstract which we have just given. He appears to be familiarly acquainted with those parts of the science which Priestley, Cavendish, Black, Lavoisier, and his associates, have investigated with so much ardour, and with such splendid success: the application also of modern chemistry to meteorology, and physiology, is a subject on which he feels himself at home, and concerning which he writes with interest. But he appears to have spent more of his time in reading than in the practical details of a laboratory. Hence his accounts of apparatus, utensils, lutes, fuel, &c. are excessively imperfect and incorrect; the same vagueness and errors, arising from a want of personal inspection and experience, in too many instances vitiate his descriptions of processes both on a large and small scale. The arrangement of the work, besides being inconsistent with itself, however prepossessing from its seeming simplicity, is very different from those generally adopted, and therefore requires a much more copious index of reference, than these volumes possess. We do not think that this system of chemistry supersedes those in common use, or is by any means equal to its lofty pre tensions. ART. II. A Series of popular Chemical Essays, containing a Variety of Instances of the Application of Chemistry to the Arts and Manufactures, &c. &c. By FENWICK SKRIMSHIRE, M.D. lately President of the Natura! History Society of Edinburgh; Member of the Royal Medical Society of Edinburgh. 2 vols. 8vo. "THE substance of the present essays," as the author observes, "is part of the materials collected with a view of delivering an experimental course of popular lectures on chemistry and natural history." He therefore does not profess to give it as a strictly scientific work, but as adapted to convey useful information to general readers. Considered in this light, the two volumes before us possess much of that kind of merit which belongs to the careful and judicious compiler: the information conveyed is on the whole accurate, and the execution respectable. It may, however, be questioned how far the reader can receive adequate instruction from a system so condensed as this. It is to put into his hands the lecturer's notebook, well arranged indeed, but deficient in the filling up, and not explained and enlivened by entertaining or brilliant experiments. Yet there is some thing so interesting in tracing the con nection between theoretical science and practical skill, that the uninformed, who peruse a work like the present, may easily be seduced into the study of the dry elementary axiom, or the meagre narrative of experimental truths. The space allotted for the different subjects is unequal, compared with their relative importance. A considerable space is very properly devoted to the subject of heat, in its various modifications; and the execution of this part is performed with so much judgment and selection, as to present a very excellent compendium of all that is known on this most interesting topic. The metals well deserve a fuller notice, especially in a work that professes to dwell peculiarly on the arts and manufactures connected with chemistry, and several errors occur, shewing, however, a want of attention, rather than of knowledge of the subject. For example, "The ores of metals are friable, have an earthy appearance, have different colours according to the degree of oxydation, and have no lustre." This last assertion is totally erroneous; the native oxyds of tin, the ruby copper ore, and many other ores, possess a beautiful lustre. The existence of gold in vegetable ashes stands on such very questionable authority, as hardly to be worth mentioning. Galvanism comes in but aukwardly under the description of zinc, merely because this metal is much employed in forming the galvanic pile. As an example of the execution of this work, let us take the manufacture of soap. "The alkalies will all of them unite with oils, and the result of such a combination is a SOAP, the kind and quality of which depends upon the kind and quality, and also upon the proportion, of the ingredients. "The first part of the process consists in making the alkali pure or caustic, by mixture with quick lime, which abstracts from it the carbonic acid, or fixed air. This caustic lie, mixed with oil or tallow in due proportion, and boiled to a proper consistence, formis soap. "Boil one part of good barilla, with two of quick lime, in a sufficient quantity of water, strain the liquor through a cloth, and evaporate till a phial, holding eight ounces of water, will hold eleven of this solution; then boil one part of the lie with two of the oil, and you will have a good hard soap. "In manufactories, where the fuel is of material consequence, the lie is made without boiling. Equal measures of barilla and slaked quick lime are heaped up together, water is poured on the top, and filtering through the heap, is caught in proper vessels; more water is then poured on, till no salt comes with it, and the lie of different strengths is kept separately. It is now mixed with the oil and tallow in boilers, the weakest lie first, then that which is stronger, and so on; and when boiled sufficiently the soap is made. The best soft soap is made with five parts of potash, three of whale oil, and one of tallow. For soaps of an inferior quality, more tallow, kitchen-grease, or oil of an inferior quality is used. And lately the French che mists have recommended a cheap soup to be made, by using woollen rags, and old woollen cloths of all kinds, locks of wool, hair, and even the horns of animals, instead of oil. These substances are all soluble in the caustic lie, and by proper boiling forma a збар. The chief inconvenience of such a soap is, that it possesses a very unpleasant smell. It is, however, used by many of the cloth manufacturers in cleansing their stuffs; and as they require repeated washings, the smell is thereby completely taken off. The most delicate soap is made with olive oil; and a peculiar kind, called Starkey's soap, is made by triturating ten parts of caustic alkali hot, with eight parts of oil of turpentine, which instantly forms a very hard soap." The subject of mineral waters is, comparatively, very full and detailed. Opportunity is taken to introduce a description of a well at Wellingborough, in Northamptonshire, which appears to be a simple chalybeate, like that of Tunbridge, and many others. The concluding articles of tanning and currying, are very good and entertaining. The work is dedicated to the gover nors of the Kettering dispensary. ART. III. A Syllabus of a Course of Lectures on Chemistry, delivered at the Royal By H. DAVY. 8vo. pp. 91. Institution of Great Britain. A SYLLABUS of lectures is scarcely an object of criticism, either as to its style or matter. The little volume before us is a concise, and, for the most part, judicious selection of the prominent facts in chemical science. The arrangement of the lectures is in some measure new, and well calculated to lead the pupil from the easiest and simplest, to the more difficult and complex phenomena, and then to shew the application of both to the purposes of the arts. The whole is divided into three parts: the first treats of the chemistry of ponderable substances, and concludes with the general laws of chemical action: the second part treats of impon derable substances, viz. caloric, light, electricity, and galvanism. The third part is entitled the chemistry of the arts, and relates to agriculture, tanning, bleaching, dying, metallurgy, glass, and porcelain, the preparation of food and drink, and the economical management of fuel. |