1 hicle of sound. Electricity in this volume; galvanism, magnetism and optics, in the other, are very valuable articles. In many parts, M. Hauy seems rather to indulge in hypothesis, and in a a willingness to account for facts, but his facts are accurate, and generally stated with clearness and precision. We shall transcribe another passage on the chemical effects of galvanic electricity, which will exhibit the author's style as a narrator of facts, his fairness with regard to philosophical discovery, and the nature of the translator's notes, which are useful and often valuable additions to M. Haüy's treatise. "522. Two learned Englishmen, Carlisle and Nicholson, having plunged two pieces of wire into water, one communicating with the upper disc of an ordinary pile, and the other with the lower disc, perceived indication of two gases, that disengaged themselves at the extremities of the wires, and which they ascertained to be the same as those which enter into the composition of water. In this experiment a curved tube is commonly used, whose two branches are filled with water to a certain height, and closed with cork, through which wires are introduced. The extremities of these wires are placed in water so as to leave an interval between them. The oxygen appears in the form of bubbles at the extremity of the wire communicating with the zinc disc, which produces vitreous electricity, and the hydrogen disengages itself, in the same form, at the extremity of the wire in the base of the pile, and gives resinous contact with the copper disc which forms electricity. If the metals are oxydable, very few bubbles are seen at the extre mity of the wire answering to the zinc disc, because the oxygen fixes itself to this wire, making it at the same time pass to a state of oxydation.* 523. This new phenomenon soon attracted the attention of the learned, and particularly of chemists whom it furnished with a problem requiring the most delicale management, to reconcile it with the theory relative to the nature of wa ter. The first point they wished to as certain was, if the oxygen and hydrogen proceeded from the same molecule of water, or from two distinct molecula. It had been remarked, that when the wires were plunged into two separate vessels, there was no disengagement of gas; but this might arise from the communication, that was necessary for the discharge of the pile to take place, being then interrupted. Mr. Daryt devised *Mr. Cruikshank ascertained that when the wire coming from the zinc end of the pile is plunged into infusion of litmus, the infusion becomes red, and an acid, which appears to be the nitric, is formed; that the wire from the silver end reddens the infusion of brazil wood, and of course an alkali is formed. He ascertained also, that the silver end wire revives metals from their salts, as had been previously known to happen whenever nascent hydrogen comes in contact with them. He thought, likewise, that he had ascertained that all liquids containing no oxygen are non-conductors of Galvanism. + This gentleman, in the course of November and December 1806, read the Bakerian Lecture before the Royal Society, On Electricity considered as to its chemical agencies.' He then shewed that the Voltaic current separates acids from their bases; so that the acids arrange themselves round the positive point, and the bases round the negative: and that this energy is so strong as to prevent the usual effects of chemical affinity. As in Volta's contacts of metals, copper and zinc ap. a very simple mode of proving, that in reality it was this interruption which prevented the gass from disengaging itself. He plunged two fingers of the same hand into the two vessels, and the gas immediately appeared." We must add that Mr. Gregory has in general performed the task of translator, as well as that of editor and commentator, with credit: we could point out some things that require alteration, had he not given an ample apology in his preface for defects of the kind to which we allude. Should the public call for another edition, he will have an op portunity of altering such sentences and phrases as the following. "To draw an example from that which is the subject of this treatise, the modern discoveries relative to the properties of the gases, and of caloric, permit not physics to be isolated from chemistry, &c." "Certain forces that solicit bodies, &c." Mr. Gregory will of course under such circumstances read the book as an Englishman, and will at once see where he has deviated from the idiom of his own language. ART. V. A Dictionary of Practical and Theoretical Chemistry, with its Application to the Arts and Manufactures, and to the Explanation of the Phenomena of Nature: including throughout the latest Discoveries, and the present State of Knowledge on those Subjects. With Plates and Tables. By WILLIAM NICHOLSON. 8vo. IT is needless to say that this is a respectable work, for it cannot be that an author so advantageously known to the public as Mr. Ni. cholson, should write any work on the subject of Chemistry which should not be worthy of attention. At the same time however we may be allowed to observe, that it is utterly impossible that the vast extent of the science of chemistry, together with its innumerable applications to the works of art and the phenomena of nature, should be adequately treated of in the compass of a single octavo volume. To detach particular passages either for praise or blame would be a very unsatisfactory method of exhibiting the volume before us. It will we apprehend be a much fairer way both towards the author and the public to go through one entire article with a running commentary. For this purpose we shall select the metal tin. With regard to the ores of this metal we have to remark, that Mr. N. has retained the Tinspar of Margraaf and the native Aurum Musivum of Bergman which are rejected for very good reasons by all modern mineralogists. He has omitted the results of the analysis of tinstone, made by Klaproth and Lampadius which are the only satisfactory authorities for the component ingredients of this mineral. The method of analysis in the moist way is given very correctly from Klaproth : the dry assay is not so accurately related; in particular, the necessity of roasting to get rid of the arsenic, which most samples of ore contain very largely, is not mentioned. The way of performing reduction in the great is very incorrectly reported, being both imperfect and errone ous. In treating of the chemical properties of tin, Mr. N. observes with regard to the oxyd of this metal : pear in opposite states; so Mr. Davy finds that acids and alkalies, with regard to each other, and the metals, possess naturally the power of affording electricities, and may be said to be respectively in states of negative and positive electrical energies; and the bodies naturally negative are repelled by negative electricity, while the bodies naturally positive are attracted by negatively electrified points. See Phil. Jour. No. 65.-TR. "The oxide of tin resists fusion more strongly than that of any other metal; from which property it is useful, to form an opake white enamel when mixed with pure glass in fusion. The brightness of its surface when scraped soon goes off by exposure to the air; but it is not subject to rust or corrosion by exposure to the weather." Thus wholly omitting all notice of Beaume's interesting experiments, and the numerous conclusive facts that demonstrate the existence of two distinct oxyds of tin. The combination of sulphuric acid with tin is represented as forming only one salt, the sulphat, whereas there are two sulphats, differing from each other both in the degree of oxydation of the metal and the proportion of acid. "Nitric acid and tin combine together very rapidly, without the assistance of heat, Most of the metal falls down in the form of a white oxide, extremely difficult of reduction; and the small portion of tin, which remains suspended, does not afford crystals, but falls down, for the most part, upon the application of heat to inspissate the fluid." This is a very imperfect representation of the matter. Highly concentrated nitric acid has no action whatever on tin at the common temperature; when diluted with a little water the rapid action described by Mr. N. takes place, but it is not mentioned that when the acid is much diluted a quiet solution of the metal is effected, and that this nitrat of tin contains the metal in the state of suboxyd, which in fact is the only state in which a combination with nitric acid can be effected. "The muriatic acid dissolves tin very readily, at the same time that it becomes of a darker colour, and ceases to emit fumes. A slight effervescence takes place with the disengagement of a fetid inflammable gas. Muriatic acid suspends half its weight of tin, and does not let it fall by repose. It affords permanent crystals by evaporation. If the tin contains arsenic it remains undissolved at the bottom of the fluid. Recent muriat of tin is a very delicate test of mercury. Mr. Chenevix says, if a single drop of a saturated solution of neutralised nitrat or muriat of mercury be put into 500 grains of water, a few drops of solution of muriat of tin will render it a little turbid, and of a smoke gray. He adds, that the effect is perceptible, if ten times as much water be added." This account of the sub-muriat is extremely imperfect. In the first place, no notice is taken of the solid sub-muriat prepared by subli mation (a totally different salt from the sublimed oxy-muriat ;) and secondly, the highly interesting experiments of Pranet and Pelletier on the deoxygenizing qualities of this salt are entirely omitted. The sub-muriat with excess of base, discovered by Berthollet, together with the satisfactory explanation thus afforded of many singular circumstances attending the decomposition of the common sub-muriat by the alkalies, are also unnoticed." In the description of the oxymuriat of tin, though some of the discoveries of Adet are mentioned, yet the equally ingenious ones of Pelletier are not hinted at, and false conclusion is drawn from the whole from the want of distinguishing between the two submuriats. The action of the alkalies on the oxyds of tin is totally passed over, though the subject has been well illustrated by the acute observations of Proust and Berthollet. The curious discoveries of Gadolin on the anomalies attending the process of wet-tinhing are very protoo much at large considering the perly noticed by Mr. N. yet rather extreme compression of the rest of the article. The action of super tartrite of potash on tin, and the triple salt thence resulting, is not mentioned, nor are the excellent experiments of Proust on the The first of the chemical manufactures that we turned to was leather dressing; under which article there is only a reference o TANNING: the article Tanning itself, consists first of an abstrae of M. de St. Real's memoir on the subject, then an abstract of . Seguin's new practice, and concludes with a few observations of M. Dismond. But of the actua prac tice of tanning, tawing, leathe dres sing, currying and dying, there is not a word. Under the article SUGAR there is a long extract from Edwards on the preparation of raw sugar in the West Indies, but on the home manufacture of loaf and candy sugar the reader will not receive any information good or bad. The unsuccessful attempt at procuing sugar from the beet root deseved more notice than it receives. The manufacture of STARCI is equally unsatisfactory: and in.hat of SOAP no use whatever is mae of Pelletier's admirable memoir of the subject. The article IRON is the mos laboured, and contains more orignal reflection and information than the rest, yet it is greatly deficier in arrangement and luminousness. We shall detach the following potion as a specimen, and not an ufa vourable one of the whole, "The fluid into which ignited steel is plunged is of great consequence. All the facts seem reducible to these general conclusions. The hardness will be greater, 1. The hotter the steel is made, provided it be not decomposed: 2. The more concooling: 3 The shorter the time of coolsiderably its temperature is lowered in the ing: and 4. The more favourable the fire or the cooling material may be to the steel-making process. But the most useful combination of hardness and tenacity will be at a medium temperature in each kind of steel. "With regard to the first particular, little need be said, but that the decomposition of steel in heating will be prevented, and its surface somewhat improved, if it be bedded in charcoal, or the cementing heat. The second and third, namely the compound, during the application of the quantity and suddenness of cooling, require an attention to the doctrine of CALORIC, as explained under that article. The cooling will be more sudden and effectual the greater the quantity of heat absorbed in the same time. There are three circumstances which favour this effect, namewhich the hot steel is applied; that it ly, a very low temperature of the body to shall be a good conductor of heat; or that it shall assume either the fluid or elastic state, which always demand a supply of heat for their maintenance. Thus it is found, that steel is more effectually hardened in cold than in warm water, and at like temperatures more effectually in mercury than in water. It may also be remarked, that these two fluids cool the steel by different energies. The water is partly converted into vapour, which carries off the heat, and leaves the fluid much less altered in temperature than mercury, which fluid, not having evaporated in the process, acts by its conducting property. This last is found to have acquired a much more elevated temperature by the immersion. Oil is found to harden the surface of steel much more than its internal part, so that it resists the file, but is much less easily broken by the hammer. This effect arises from its imperfect conducting quality, and the elevated temperature it demands to be converted into the vaporous state; to coal is formed round the steel from the which we may also add, that a stratum of burned oil, which still more effectually prevents the transmission of the heat. A remarkable instance of this nature presented itself to my observation in hardening a small piece of steel two inches long, and a quarter of an inch diameter. At the time of ignition, the water nearest at hand had been used with soap. The steel made very little noise when plunged into the water, and remained hot for a considerable time; but when taken out was found to be scarcely at all hardened. It was covered with coally matter; which being cleared off, and the process repeated with clean water, it became perfectly hard. The heat in both cases was a low red heat, proper for cast steel, which is not intended to be afterwards annealed. I have very little doubt, but that alcohol and the essential oil of turpentine, which are good conductors of heat and very volatile, would render steel very hard, if their inflammability, and the little necessity there is for using them, were not an impediment to their application Various artists avail themselves of different substances for the immersion of ignited steel. Some use urine, others water charged with common salt, nitre, or sal ammoniac. Taliow and oil are used for such works as are not required to be brittle, though very hard, the reason of which has just been mentioned; but tallow differs from oil in the heat which becomes latent for its fusion; and accordingly, solid tallow is an excellent material for hardening drills and other small articles. It has been found by Reaumur, that saline liquids produce rather more hardness than common water; and in particular, that aqua fortis possesses this property in an eminent degree, probably from its conducting power: the makers of files cover them with the grounds of beer and common salt, which assist their hardening, and keep the surface from scorifying. The mucilage of the beer supplies a coally mat ter; and the fused salt seems not only to form a varnish in the fire and defend the steel, but may also produce cold, by its sudden solution in the water at the time of immersion. Very small articles heated in a candle are found to be hardened per fectly by suddenly whirling them in the cold air; and thin bars or plates of steel, such as the magnetic needle of a compass, acquire a good degree of hardness by being ignited, then laid on a plate of cold lead, and suddenly covered with another plate. These would be unequally hardened, and bend, if plunged in water. "The Ulueing of steel appears to affect its elasticiy in a manner not easily explained. This operation consists in expos ing steel, the surface of which has been first brightened, to the regulated heat of a plate of netal, or a charcoal fire, or the flame of a lamp, till the surface has acquired ablue colour. Now, if this blue coat be removed by grinding, the elasticity is completely destroyed, and may be restores by blueing the stel again. Rubbing with sand or emery-paper, glazing, orburnishing, equally impairs the elas ticity in proportion as it destroys the blue coat. Sawmakers first harden their plates in the usual way, in which state they are brittl and warped: they then soften then by blzing, which consists in smearing the plate with oil or grease, and heating it till thick vapours are emitted, and burn off witha blaze; and after this they may be hammered flat; lastly, they blue them on a ho iron; which renders them stiff and elasic without altering their flatness." ART. VI. A new System of Chemical Philosphy. Part I. By JOHN DALTON. 8vo. OUR scientific readers are acquainted with the author of this work, both as an experimentalist, remarkable for the simplicity of his apparatus, and as a theorist, who has proposed some ingenious and novel speculations. His opinions have heen hitherto given to the world only in detached essays, which have occasionally appeared in different periodical works. He has now, however, entered upon a PP. 22. |