reviewer, however, evidently wished to represent it as a great mistake; and at first sight it certainly would have been so : none knew, however, better than the reviewer, that his observations were intended to deceive, and that his criticisms were really unfounded. having in the hurry of the moment been mistaken for 112 lb. It would, indeed, be difficult to imagine how "so enormous a blunder could have been perpetrated in the first instance," but it is not, perhaps, SO truly marvellous" as the reviewer seems to imagine, that the error should have escaped me while correcting the proof sheet, when it is considered that my book was printed in the country, at some considerable distance from my residence, and that it was brought out in monthly parts, so that much hurry | was requisite in order to get the numbers in London ready for delivery by the ap-rity, and see the extent of my inaccuracy in pointed time. I am well aware, Gentlemen, that it is very rarely that the excuses offered by authors in extenuation of mistakes which have been allowed to creep into their works are admitted by the public, but I cannot help feeling and saying, that in the present instance I have been dealt with rather too severely; and that much calculation and labour expended by the reviewer to point out the absurdity of my statement might have been saved. a My next mistake consists in stating that the 1438 grains of oxide left after heating 1638 grains of peroxide of manganese, is " mixture" of 992 grains of deutoxide and 446 grains of protoxide of manganese. Let us now turn to another high chemical autho this instance. In Professor Graham's Elements of Chemistry, page 244, the following passage occurs:-"Three equivalents (1638 parts) lose two equivalents of oxygen (200 parts) and leave a compound of one of deutoxide and one of protoxide." In this case, then, the Editors of the Philosophical Magazine are obliged to withhold their approbation from my work, because I employ the word "mixture" instead of the word " compound:" this is actually the full extent of my mistake!! I now come to the master-piece of the whole review-to the grandest and most profound effort of all.-A "mistake" is next noticed, which must eternally condemn my Lectures on Chemistry, and stand for ever as a "monumentum perenne" of the pene I am next found fault with for saying that four gallons of oxygen gas is the maximum quantity obtainable from 1 lb. of peroxide of manganese, "of good quality," and the reviewer has been at the pains to calculate the quantity which ought theoretically to be obtained from 7000 grains, or 1 lb. avoirdu-tration and sagacity of the reviewer. "We pois, of absolutely pure peroxide, and which he finds to be 8 gallons::-now if, Gentle men, you will have the goodness to refer to my book (page 143), you will find that the candid (?) reviewer has presumed to omit the word "about," and to insert the words, "of good quality;" the passage runs thus, "we are here supposing the peroxide to be pure, which it never is, as met with in commerce; we may consider four gallons of gas from one pound to be about the maximum obtainable quantity." Let us, however, see what Dr. Kane (one of the Editors of the Philosophical Magazine,) says himself on the subject, in his Elements of Chemistry. In page 394, I find the following remarks: Hence, 1 lb. Troy is capable of furnishing seven imperial gallons of gas. The oxide of manganese found in commerce is not, however, pure; in general, it does not contain more than 65 per cent. of pure oxide, and hence the quantity furnished by a pound of it is about two-thirds only of that just stated—that is, of 7 gallons, or 4 gallons." Where the great difference can be between " 4 gallons," and "about 4 gallons," I cannot perceive; and I think it will be agreed by every impartial person, to make it a subject of public reprehension savours strongly of hypercriticism. The are informed that half an ounce of chlorate of potash (218·75 grains) should yield 270 cubic inches of oxygen gas, he having just before stated that 1532 grains yield 600 grains of oxygen; 218.75 therefore give 85.7 grains, measuring only 249 instead of 270 cubic inches." Now, Gentlemen, whatever may be thought of the other strictures on my book, it will undoubtedly be acknow. ledged by all, that this, to say the least of it, is a very great miss on the part of the reviewer. Let me first quote the passage as it actually stands in page 144 of my book: "1532 grains of chlorate of potash yield 600 grains of oxygen, and 932 grains of chloride of potassium, practically, half an ounce should yield 270 cubic inches, or nearly a gallon of pure oxygen gas.' I will first test my statement by Professor Graham's work, page 247" Half an ounce of chlorate of potash should yield 270 cubic inches, or nearly a gallon of pure oxygen gas." I will now see what Dr. Kane says, and in quoting from his work, let me particularly impress upon the readers of this vindication, that Dr. Kane is himself one of the Editors of the Philosophical Magazine, and as such is responsible for any review which it may contain. In Dr. Kane's Elements of Chemistry, then, page 396, I find the following passage :-" Hence 100 parts of chlorate of potass give 39 of oxygen by weight, or an ounce Troy, 187 grains, or 543 cubic inches." Now, if an ounce will furnish 543 cubic inches, it will be admitted, I presume, that half an ounce should furnish 271 cubic inches, or practically 270 cubic inches, as I state in my book. It never, I suppose, occurred to the reviewer, whilst penning his strictures on my work, that the ounce may have two values;-that there is such a thing as the Troy ounce = 480 grains, as well as the avoirdupois ounce =437 grains, perhaps he did not know this;perhaps, however, he may rejoin, "You have no business to employ Troy weight in your calculations:" be it so-but then, my good friend, have you never heard the vulgar saying," Those who live in glass houses should not commence throwing stones?" I had clearly as much right to allude to the Troy ounce as Dr. Kane had; besides which, we find Professor Graham doing the same, so it is not so unusual a thing after all. I will not occupy your space by any remarks on the evident desire to find fault, evinced by the foregoing quotations; but as I have already trespassed somewhat largely on your pages, I will briefly allude to the two remaining "errors", which have been selected for animadversion, and then leave the matter for the consideration of your readers, without one word of comment. Note, page 144, "I find that the best chlorate of potash 'yields from 96 to 98 per cent. of pure oxygen."-"For some time," says the reviewer, 66 we were puzzled to attach any meaning to this statement, but at length we concluded that the following is what the author meant: -I find that 100 grains of the best chlorate of potash yield from 96 to 98 cubic inches of pure oxygen gas." The "author," however, meant nothing of the sort; and although I am ready to admit that the sentence might have been worded better, any person whose understanding was not intentionally dulled, would immediately have understood the meaning to be this :-"The gas from chlorate of potash is not absolutely pure; it contains from 96 to 98 per cent. of real oxygen gas." I here allude to the best chlorate of potash that is met with in comwhen the salt was prepared with scrupulous attention, and the gas obtained with the greatest care, Gay-Lussac could only detect an impurity amounting to 4 volumes in 1000. merce: . Lastly, it was thought worth while to animadvert on the following passage:From an equivalent of oxide of mercury we get 100 grains or nearly 300 cubic inches of nitrogen gas, and 1266 grains of mercury are found in the receiver." "It | should have been stated," observes the reviewer, "that from 1366 grains, which may be considered as representing an equivalent, &c. :" and the passage is quoted as exhibiting "an extraordinary degree of confusion," though with what justice others must determine. Such, Gentlemen, are the "errors" which oblige the Editors of the Philosophical Magazine to withhold their approbation from my Lectures on Chemistry. I remain, Gentlemen, Your obedient servant, HENRY M. NOAD. THE ELECTRICAL MAGAZINE. Conducted by Mr. CHARLES V. WALKER. London: Simpkin, Marshall and Co. No. I. THIS Magazine, the publication of which we announced in our last No., has fully realised our anticipation, and will fill up a vacuum in scientific literature. The publication of the Proceedings of the Electrical Society having ceased, the necessity for a work like the present, would have been more deeply felt. The Electrical Magazine is a faithful reporter of the discoveries in Electricity within the period of publication in this country and on the Continent, and we hail this new laborer in the field of Physical Science. The present No. contains articles by Karsten (On Electric Pictures), Bunsen, De la Rive, Becquerel, Boquillon, Morren, Dr. Elice, Matteucci, Mr. Bain, and Mr. J. P. Gossiot; under the heading of Scientific Meetings, we have abstracts of papers read at the Royal Institution, the Institution of Civil Engineers, and the Society of Arts, by Prof. Faraday, Prof. Grove, Mr. Smee, Mr. F. Pellatt, Professor Wheatstone, and Mr. Cooke. The Electrical papers of the various English Journals are also presented to the reader in a condensed form. We recommend such of our readers as devote a portion of their time to the study of Electrical science to subscribe to this truly valuable Magazine, and we wish the editor every success in his undertaking. THE BRITISH QUARTERLY JOURNAL OF DENTAL SURGERY. London: John Churchill. No. II. THIS No. fully maintains the character of the first, and is quite as much entitled to our commendation. It is replete with highly interesting matter. PHOTOGENIC MANIPULATION: Containing Plain Instructions in the Theory and Practice of the Arts of Photography, Calotype, Cyanotype, Ferrotype, Chrysotype, Authotype, Daguerreotype, and Thermography. By GEORGE THOMAS FISHER, Jun. Illustrated by Woodcuts. London: George Knight and Sons. A VERY excellent little work, and one which those who desire to perform any of the processes mentioned in the title, cannot do better than purchase. One shilling, thus expended, will procure more really valuable information than is often obtained for five times that sum. BOOK RECEIVED. PRACTICAL DIRECTIONS IN THE PREPARATION OF AERATED WATERS, and the Various Compounds of Carbonic Acid Gas, by Bakewell's Patent Apparatus: with Observations on the Pharmaceutical and Therapeutical Agencies, and their Efficacy in the Cure of some of the most Important Diseases of the Human Body, viz., Indigestion, Nervous Atony, or Mental Depression, &c.; with Cases in Illustration. By ROBERT VENABLES, M. B. London: G. Knight and Sons. [A very useful little work, which will be noticed in our next.] NOTICES TO CORRESPONDENTS. "A CONSTANT READER OF THE CHEMIST" shall hear from us by post according to his request. "A. M."-First wash the warts with warm water, or a solution of caustic potassa, or scrape the surface of them with a knife; then apply concentrated nitric acid. Repeat this treatment several times, until the object is effected. The nitric acid must be allowed to dry on. After trying this, let us know the result; and, if necessary, we will advise again. "R. C., WHITBY," shall hear by post. More letters from Members and Associates of the Pharmaceutical Society! We are glad to find that our arguments have had so beneficial an effect. THE CHEMIS T. ON BUTYRIC ACID.* I. CHEMISTRY. BY MM. PELOUZE AND GELIS. BUTYRIC acid was discovered in 1814, among the products of the saponification of butter, by M. Chevreul, who has given its history with much care in his work on the fatty bodies of animal origin. Since that period, butyric acid has not been the subject of any extended investigation, which must doubt. less be attributed to the length and difficulty of its preparation, which are so great, indeed, that butyric acid is still but rarely met with in chemical laboratories. However, M. Simon has already made known some of the properties of butyric ether, of which M. Chevreul had already some idea, and which he appears not to have obtained in a state of purity. Bromeis (Annales de Chémie et de Physique, tome vii., 3e Série) repeated in the laboratory at Giessen, the analysis of butyrate of baryta, on some fine crystals of that salt prepared by M. Chevreul himself, and sent by him to Professor Liebig. On the other hand, Nöllner has described, under the name of pseudo-acetic acid, a peculiar acid arising from the spontaneous fermentation of tartrate of lime; and Berzelius ascertained, by the examination of a sample of pseudo-acetate of lead sent to him by Nöllner, that the acid discovered by this chemist was a mixture of acetic and butyric acids. In repeating the experiments of M. Frémy on the remarkable modification which sugar undergoes in the presence of animal membranes, and those of Boutron and Frémy on lactic fermentation, we have observed several curious results. If sometimes, indeed, the conversion of milk into lactic acid, under the influence of caseum, is simple and complete, most frequently, and without its being necessary to co-operate in different conditions to those indicated by those skilful chemists, the most complicated reactions are observed. * Comptes Reudus, No. 23, June 12, 1843. N. S. VOL, I,No, IX., September, 1843. All the substances which are capable of furnishing lactic acid, have the same composition as that acid; or, if they differ from it, it is only in containing a little more or a little less water; the lactic fermentation consists, then, in a simple molecular change, with or without fixation of water, but always without disengagement of gas: however, in a great number of cases we have observed it become effervescent, like alcoholic fermentation; and, which is a remarkable thing, we have constantly found pure hydrogen amongst the gaseous products. This fact reminds us of an observation of M. Desfosses, which has hitherto remained unexplained. This chemist had detected the existence of a slight disengagement of hydrogen in analagous fermentations; but as, in our experiments, we sometimes obtained this gas in very great quantity, we thought it necessary to investigate the cause of its formation, and we have been fortunate enough to ascertain that it is due to a new fermentation, during which, in place of the sugar which disappeared, we observed the formation of one of the products of animal organisation, one of the acids of butter, in a word, butyric acid. This observation will necessarily occupy an important place in the present discussion concerning the formation of fats in animals. Without wishing in any way to guess at the means which nature employs in the very numerous modifications which it causes aliments to undergo, we cannot help remarking that the conversion of sugar into butyric acid is effected without the intervention of any considerable elevation of temperature, and without the employment of any of those energetic reagents capable of destroying the equilibrium and vitality of the animal economy, but that this conversion takes place, on the contrary, in very simple conditions and with matters which living nature presents to us. If this resemblance has any appearance may be the same with the ordinary fatty acids of foundation, it may be conceived that it 3 D relative to butyric acid and to sugars, as well as to starch, which in so many respects resembles these last bodies. After many experiments relative to the best process to be followed for obtaining from sugar the greatest possible quantity of butyric acid, we have stopped at the following method : mains almost stationary. This is an indication that the acid which distils over is concentrated. It is collected by continuing the distillation until the retort contains only a small quantity of acid mixed with a little coloring matter, chloride of calcium, and butyrate of lime. The acid is boiled for some time to free it from a few traces of hydrochloric acid, and is again distilled. It is then perfectly pure. The first portions distilled are not lost; they are used for the preparation of butyrates; or else, mixed with chloride of calcium, a fresh quantity of concentrated butyric acid may be obtained from them. Add to a solution of sugar, marking 10| degrees of the saccharometer, a small quantity of caseum and sufficient chalk to saturate all the butyric acid which is afterwards formed this mixture is left at a constant temperature of from 75° to 85° F.; it very soon undergoes profound alterations; the fermentation, at first viscous, afterwards lactic, gradually becomes butyric; these decompositions are sometimes successive, sometimes simultaneous, without it being possible to regulate their progress. The disengagement of gases becomes more abundant, and, in submitting them to analysis, a period arrives when the free hydrogen amounts to one-third of the volume of carbonic acid. At this period, the butyric fermentation is in all its force; when, finally, at the end of several weeks, all disengagement of hydrogen has ceased, the operation is finished, and the liquor no longer contains anything but buty-result. rate of lime. Having remarked that the conversion of sugars into butyric acid was apparently effected so much the more easily as we operated on more considerable masses, we have submitted to fermentation such quantities of sugar that we have been able to procure 20 or 25 kilogrammes of butyrate of lime. The extraction of pure butyric acid from butyrate of lime is easy; it is executed in the following manner : One kilogramme of butyrate of lime is moistened with from three to four kilogrammes of water to which from three to four hundred grammes of commercial hydrochloric acid have been added. This mixture is introduced into a distilling apparatus, and it is boiled until 1 kilogramme of distilled liquid is obtained from it. This liquid is a mixture of water, butyric acid, and a small quantity of acetic and hydrochloric acids. It is put in contact with chloride of calcium which determines the formation of two liquids of different densities. That which remains at the top is butyric acid; that which is most dense contains the other matters. The lightest liquor is removed and submitted to distillation in a tubulated retort furnished with a thermometer. The first portions which pass into the receivers are more or less aqueous; the boiling point, at first not very high, very rapidly mounts to 3179 F., at which point the temperature re COMPOSITION OF BUTYRIC ACID. M. Chevreul did not analyse butyric acid in the free state, but only in combination with the metallic oxides, and he deduced from his analysis the atomic formula Cs H1 03, for the real acid, as it exists in the anhydrous butyrates—for example, in that of lead. Berzelius proposed substituting for the above formula Cs H10 O3, in order to do away with the odd number of atoms of hydrogen which it presents. Bromeis (op. cit.) was led to a different He admits the formulæ C8 H2O. We think that we may assert that not one of these three formula is correct, and that they must be replaced by the atomic numbers CS H14 03 H O, which represent monohydrated butyric acid. The analyses which led us to establish this composition were made with extreme care, and controlled by many different means. They are in harmony with the constitution of butyrate of silver, butyric ether, and butyrate of methylen.* We hasten to add that M. Chevreul had put beyond doubt the relation of 1 to 3 between the oxygen of the base and that of the butyric acid in the series of neutral butyrates, and that he likewise rendered probable the existence of eight atoms of carbon in each atom of acid. The composition of butyric acid, its proportion which amounted, in many experi ments, to above one-third of the weight of the sugar, the disengagement of free hydrogen and of carbonic acid (independently of that evolved from the chalk), allow us to suppose that, under the prolonged action of ferments, sugar is decomposed in the following man ner : *Free butyric acid is isomeric with acetic ether and aldehyd. We have in vain endeavored to produce it with the first of these two substances. |