2. On the chemical constitution of Isethionic acid and Taurin.-By the distillation of isethionate of potash with perchlorid of phosphorus, Kolbe has obtained a new acid which has the empirical formula C4H6CIS2O5, and which he terms chlorethyl-sulphuric acid. This acid yields taurin by the substitution of NH2 for Cl, and ethyl-sulphuric acid C4H6S2O6 when the chlorine is simply replaced by hydrogen. Kolbe draws a parallel between the derivatives of carbonic and sulphuric acids, which is best illustrated by the following tabular view: C202.02 Carbonic acid. HO. (C4H5)(C2O2). O Amidoethyl-carbonic acid. HO. (C4H4(HO2)),(C202),O Oxethyl-carbonic acid Lactic acid. S204.02 Amido-ethyl-sulphuric acid. HO. (C4H4(HO2))S2O4, O Oxethyl-sulphuric acid. The author promises a more detailed account of the compounds and reactions referred to in the above brief preliminary notice.-Ann. der Chemie und Pharm., cxii, 241. 3. Researches on the atomic weight of Graphite.-BRODIE has communicated an exceedingly interesting and suggestive memoir on the atomic weight of graphite, considered as an allotropic form of carbon, the fundamental idea being that the different modifications of the same substance may exhibit a difference in equivalents, as well as in their ordinary chemical and physical properties. The author finds that graphite, when heated with nitric acid and chlorate of potash, increases in weight, and ultimately yields a light yellow crystalline substance. The details of the process are as follows: a portion of graphite is intimately mixed with three times its weight of chlorate of potash, and the mixture placed in a retort. A sufficient quantity of the strongest fuming nitric acid is added to render the whole fluid. The retort is placed in a water-bath, and kept for three or four days at a temperature of 60° C. until yellow vapors cease to be evolved, The substance is then thrown into a large quantity of water and washed by decantation nearly free from acid and salts. It is then dried in a water-bath, and the oxydizing operation repeated with the same proportion of nitric acid and chlorate of potash, until no farther change is observed. This is usually after the fourth time of oxydation. The substance is then to be dried, first in vacuo, and then at 100°. By placing the mixture in a flask exposed to sunlight, the change takes place more rapidly and without the application of heat. The formula of the body thus obtained is C22H4O10, or, as the author writes it, CH4O5. Its crystals belong either to the right or oblique prismatic system. It is insoluble in water, containing acids or salts, and very slightly soluble in pure water. It unites with alkalies, and the crystals have an acid reaction ammonia converts it into a transparent jelly, but the substance is not dissolved. Acids separate it from this combination, as a gelatinous mass resembling silica. Treated with deoxydizing agents, it is readily decomposed. When a solution of sulphate of ammonium or of potas sium is poured upon the dry substance, a crackling sound is heard, and a body is formed resembling graphite. The crystals are decomposed with ignition on the application of heat, gases being evolved, and a black residue left, which resembles finely divided carbon. This substance the author proposes to term graphic acid. When graphic acid is heated in naphtha to about 270°, water and carbonic acid are given off, while the naphtha takes a deep red color. The residual substance resembles graphite and has the formula C44H2O8, or with the author's equivalents, C22H2O4. When this substance is heated in a current of nitrogen to a temperature of 250°, water is given off with a little carbonic acid; the substance remaining is found to have the formula C132H4O22 or C66H4O11. This body may be exposed for several hours to a red heat in a current of nitrogen without losing all its oxygen and hydrogen. The author compares graphic acid with a remarkable compound of silicon discovered by Buff and Wöhler, which has the formula Si4H4O5, and which was obtained from the graphitoid form of that element. The properties of the two substances agree very closely, whence it may be inferred that the graphite compound is the same term in the system of carbon as the silicon compound in the system of silicon. The total weight of graphite which in the compound is combined with atoms of hydrogen and of oxygen is 132. If we assume that this weight is like the corresponding weight, 84 of silicon, to be divided into four parts, we arrive at the number 33 as the atomic weight of graphite. Representing this weight by the letters Gr, the formulas of the substances C11H405, C22H2O4, and C66H4011 become Gr4H4O5, Grs H2O4 and Gr24H4O11, where 0 16. According to the law of Dulong and Petit, the specific heats of the elements are inversely as their equivalents. The elements are divided into two classes, one in which the product of the specific heat into the equivalent is about 3.3-the other in which this product is 6.6. The specific heat of carbon in the form of graphite-0-20187-presents a remarkable exception to the law, if we take its equivalent as 6 or 12, but if we assume the atomic weight of graphite as 33, we have for the product of the specific heat into the atomic weight, the number 6.6 which is according to the law of Dulong and Petit. The relation which exists between the atomic weights of boron, silicon and zircon, and that form of carbon for which a place may be claimed as a distinct element, graphon, is precisely the kind of numerical relation. which is found to exist between the weights of analogous elements. We have These considerations lead to the inference that graphite functions as a distinct element, forming distinct combinations with a distinct equivalent, viz: 33. How far this inference may be extended to the allotropic forms of other elements, experiment alone can decide.-Quart. Journal of Chem. Soc., vol. xii, p. 261. [Note. With respect to the numerical relations between the eqs. of boron, silicon, graphon and zirconium which Brodie points out, it may be remarked that boron-at least with the equivalent 11-is triatomic, as shown by the density of the vapor of BCl3 and other considerations. It cannot, therefore, with this equivalent, belong to the same natural group with silicon and zircon, which are diatomic, as shown by recent investigations. Marignac has established the isomorphism of SnF2+KF with SiF2+RF, while Troost and Deville have shown from the vapor-density of chlorid of zirconium that its true formula is ZCl2-2 vols. or ZaCla if we assume that all compounds correspond to 4 vols. in a gaseous state. The vapor density of SiCl2 also agrees with the supposition that silicon is diatomic, supposing it to represent 2 vols. The true equivalents of silicon and zirconium become therefore respectively 14 and 44 or 28 and 88, if we admit the 4-volume theory. The equivalents of carbon, silicon and zirconium are then to each other as 6, 14 and 44, or as 12, 28 and 88, the common difference being 8 or 16 nearly. The formula Si4H4010 was deduced by Buff and Wöhler upon the supposition that the equivalent of silicon is 21, the element being triatomic as assumed by Berzelius. But if we take 14 as the true equivalent, the formula for the same compound becomes Si6H4010, and comparing with this the formula C22H4O10 we have 132 parts by weight of carbon, representing 6 eqs. of graphon instead of 4, as assumed by Brodie. This gives 22 as the equivalent of graphon, instead of 33. If now we multiply the spec. heat of graphite as found by Regnault, namely 0-201, by 22 we have 44 so that the spec. heat of an atom of graphon does not obey the laws of Dulong and Petit, as the product should be either 33 or 66. It may, however, be remarked that the spec. heat of graphitoid silicon has not yet been determined, and that there may be other classes of elements whose atoms have the intermediate spec. heats 44 and 5.5. The formulas of Brodie's compounds become, if we take the equivalent of graphon as 22Gr6H4O10, Gr12H2O8, Gr18H4O22, (taking 0-8 and not with Brodie as 16). No probable relation can be pointed out between the numerical values of the equivalents of graphon and of other elements, until we know to what natural group graphon belongs, since it is not certain or even very probable that the allotropic modifications of the same element belong to the same group.-w. G.] W. G. 4. On the Cause of Color and the Theory of Light; by Mr. JOHN SMITH, M.A. (Read by his brother, Dr. R. A. Smith).—The author, in attempting to explain certain natural phenomena, could not satisfy himself by applying the principles of either theory of light, and said that many natural phenomena indicated beats or vibrations in the luminous ether very different from what science taught. That is, that there were greater intervals between them than Newton had demonstrated and scientific men believed. He therefore endeavored to contrive experiments by which he would be able to make as many revolutions or beats in a second as he considered the effective vibrations of light were repeated in a second of time, and argued that by certain contrivances to produce light and shade in alternate vibrations he should produce color. A series of experiments was subsequently undertaken, which led to the conclusion that varieties of color are produced by pulsations of light and intervals of shadow in definite proportions for each shade of color. That is, supposing white light to consist of the motion of an ether, blackness to consist of an entire absence of motion, then a certain color, blue, red, or yellow, will be produced by the alternate action of the light and the shadow. The author used shadow in the positive sense as the sensation was positive. On pursuing the inquiry, he first caused a small parallelogram cut in card board to revolve over a black surface with a rapidity which he considered equal to the vibration of light. By this motion he obtained a distinct blue, while at another time in different weather he obtained a purple. He then made a disc with several concentric rings, which he painted respectively. 3, 4, and black, leaving the remainder white, and on making this disc revolve the rings became completely colored. There was no appearance of any black or white. In a bright day with white clouds in the sky, the rings were colored respectively a light yellowish green, two different shades of purple, and a pink. By using discs of a great variety of shapes and different proportions of white and black, the author said that he produced successively or together all the colors of the rainbow, although he had not yet arrived at the exact arithmetical determination of the amount of light and shade needful for each color. These experiments were made before the Society by the light of a paraffin oil lamp with a reflector. The author said that they were much more brilliant by sunlight. There was another set of experiments which the author considered as very effective, and especially as being easily made and described, but requiring strong sunshine to show them. These were made by casting a shadow of a particular figure on a white wall or on a sheet of paper, so as to produce alternate beats of light and shadow when put in revolution. The figure became colored of different shades, and because these could be seen on the wall, like the spectrum from the prism, he called them spectra by reflection. He mentioned also that the colors may be produced by making a black disc, with figures cut out of it, revolve before a white cloud or white screen. There were many others which he had no time to enumerate, much less to describe, but he described some of the figures which produce the phenomena which are perceived when looking through transparent solids. The author considered that his theory gave an entirely new and simple explanation of the phenomena of refraction through the prism, and summed up as follows: The experiments prove the homogeneity of the ether. They prove the undulatory hypothesis, but oppose the undulatory theory. They enable us to dispense with the different refrangibilities of the rays of light, as taught by Newton. They help to explain many of the phenomena of what is called the polarization of light. They give a new explanation of prismatic refraction, and explain in a plain and simple manner many very interesting natural phenomena. Startling, he said, as these conclusions are to those who are conversant with the subject of light, he thought he was perfectly warranted in drawing them from his experiments. The general process of reasoning could not, however, be given in a short abstract.-Ordinary Meeting, Oct. 4th, 1859, Manchester Literary and Phil. Society. TECHNICAL CHEMISTRY. 1. Vegetable Parchment.-Papyrine.-The interesting substance obtained in 1846 by Poumarède and L. Figuier (Comptes Rendus, xxiii, 918; see also this Journal xxviii, 431,) by immersing bibulous paper in partially diluted sulphuric acid-called papyrine* by its discoverers-which with the exception of a few comparatively unimportant applications in France, where it was used for the shelves on which silk-worms are reared, &c., had excited scarcely any interest other than that naturally attaching to it as a chemical curiosity, until patented (Dec. 6, 1853) in England, by Gaine, (see Rep. of Pat. Inv. [E. S.] xxiv, 151) and manufactured by the well known house of De LaRue & Co., of London, has recently been investigated by Prof. A. W. Hofmann, (Ann. Ch. u. Pharm., Nov. 1859, cxii, 243; from a report to Messrs. Thos. De LaRue & Co.) In its prominent properties it resembles ordinary parchment very closely indeed the two can hardly be distinguished from each other except on close inspection. Both exhibit the same peculiar pale, yellowish tint, the same degree of translucency, the same half fibrous, horn-like texture. Like animal parchment, the artificial product is not easily torn: it may be repeatedly bent or folded without exhibiting any special appearance of breaking in the creases formed. Like ordinary parchment it is extremely hygroscopic, and becomes more pliable by absorbing moisture. When wet with water it comports itself like untanned skins, swelling up to a slippery mass through which water cannot pass except by endosmose : the coherence of the substance is not at all impaired by thus soaking. Vegetable parchment is best prepared by immersing unsized paper during a few seconds in oil of-vitriol which has been diluted with half its volume of water, and immediately afterwards washing it in a dilute solution of ammonia; a thorough washing with pure water completing the process. Hofmann has ascertained by direct experiment that not less than one-fourth volume, or more than one-half volume, of water must be used with one volume of monohydrated sulphuric acid, in preparing the acid bath. The paper must not be immersed too long, nor should the temperature of the bath be higher than about 15° (C.)=[59° F.] A considerable amount of practice is moreover requisite before one can obtain a perfectly satisfactory product. When paper is transformed into vegetable parchment it undergoes no appreciable increase in weight. The action * Should not this term, which has an undoubted right of priority, be preserved as the scientific name of the substance?-[F. H. S.] |