sion process will always be slow in comparison, and will therefore determine the observed reaction velocity in all cases, except of course the anomalous ones already mentioned. potassium salt. Those, however, in which the sulphuric acid was 5 molar were made with ammonium ferric alum, after special tests had shown that the two alums gave practically identical results. If this hypothesis of Nerast's is to be understood Cadmium.- Experiments with metallic cadmium (Kahlliterally, it means that the observed velocity of a reaction baum's) are recorded in Table I. Here, and in all the folbetween a solid and a dissolved substance will never towing tables, k, is the observed velocity constant uncorrepresent, even approximately, the true rate of the chemi-rected, k is the same corrected for variations in the rate of cal reaction. No place is lett for cases other than those in stirring, and K the averaged value of k for the single exwhich the velocity is governed solely by diffusion and periment. By way of illustration, data for Experiment I those rendered abnormal by disturbing influences. From are given in full. For the rest only the corrected velocity this it follows that when the same dissolved substance re- constants are recorded. ac s with different metals the velocity of the reaction, in all cases free from secondary disturbances, should be the same irrespective of the specific nature of the metal. This test of Nernst's hypothesis is applied in the experiments to be described. EXPERIMENTAL PART. The method and apparatus used have been described in a previous article (Am. Journ. Sci., xxxii., 207, and in part, xxix., 237). Such minor modifications in the procedure as were found desirable in dealing with the different reactions will be mentioned in their proper connection. The different metals, in the form of circular discs 0'5 mm. in thickness and 38.3 mm. in diameter, were exposed to the action of the solution under carefully regulated conditions as to temperature, rate of stirring, and position of the disc. Samples of the solution, which was initially 600 cc. in volume, were taken at convenient intervals with a 20 cc. pipette, and the velocity constants k calculated in the ordinary way from the observed concentrations at the beginning and end of the five to ten-minute time intervals. The rate of stirring was kept at 200 revolutions per minute in all experiments, and although the variations were usually very small, they were systematically determined and corrected for by the method described in the article just cited. The temperature was 24.6° C. in all experi ments with ferric salts, and 25° C. in all those with chromic acid. Rates of Solution in Ferric Sulphate. Previous experiments on the rate of the reaction between ferric sulphate and metals have been made by T. E. Thorpe, 1882 (Fourn. Chem. Soc., xli., 287), and by C. G. Schleuderberg, 1908 (Fourn. Phys. Chem., xii., 574). Thorpe compared the action of the ferric salt on zinc, magnesium, and iron, but under poorly defined experi mental conditions, further complicated by the evolution of hydrogen. Schleuderberg studied only the reaction between ferric sulphate and copper, so that his work affords no comparison between the rates for different metals. Though primarily interested in testing for a possible effect of light on the reaction velocity, he was led to the conclusion that diffusion was the determining factor. In the experiments of the writers, the ferric alum solutions used were approximately 0.05 molar with respect to RFe(SO4)2, and contained besides various known amounts of free sulphuric acid, together with a little ferrous sulphate to take up dissolved oxygen. Several litres of solution were prepared at one time, and the total iron concentration determined once for all by reducing duplicate samples in a Jones reductor and titrating with 0 02 normal permanganate. The ferrous iron concentration at various stages of the reaction was found by direct titration with the same permanganate solution in the presence of phosphoric acid, and the ferric iron obtained by difference. In the tables, C is the total iron and c the (variable) amount of ferrous iron contained in 20 cc. of solution, all expressed in cubic centimetres of the o'02 normal permanganate. The values of C-c were used in calculating k. To prevent oxidation of the ferrous salt in the solution by the stirring in contact with air, an atmosphere of carbon dioxide was maintained above the liquid by passing a brisk current of the gas into the reaction vessel throughout the experiment. In most of the experiments the ferric alum used was the Although it might be expected that an increase in acidity would raise the reaction velocity, it is seen in the table that precisely the reverse is true, at least for concentrations of sulphuric acid above 0.25 molar. This effect will be observed in all cases where free sulphuric acid is present, whether the oxidising agent be ferric salt or chromic acid. Iron.-Results obtained with metallic iron are shown in Table II. The first experiment, as before, being recorded in detail as an example. The calculation of the constants from the titrations is here somewhat different, since for every two molecules of ferrous iron formed by reduction of the ferric sulphate one more is formed by solution instant is therefore measured by the value of the expression of the metal. The concentration of ferric salt at any C-co-3(c-co); in which C is the total iron, co the initial in the same units. In the table these units, as before, are ferrous iron, and c the ferrous iron at time t, all expressed values refer to 20 cc. of solution. The metal used was cubic centimetres of o'02 normal permanganate, and the "American ingot iron," a special grade of commercial iron which has a purity of about 99.9 per cent. For the lower acidities, o'or and o'05 molar, the results are less trustworthy than the rest and probably slightly too low, for the disc became covered during the experiment with a blackish coating which seemed to consist chiefly of hydroxide, since it turned to a rust-red colour on drying. In the presence of o 25 molar sulphuric acid the coating was very slight, and at higher acidities entirely absent. Nickel.-Table III. contains the results of the experiments with metallic nickel. Two samples of "pure nickel were used-one furnished by Kahlbaum the other of unknown origin-both of which seemed to give practically the same results. The former was used in Experiments I and 2, the latter in Nos. 3, 4, and 5, and also in the experiments with chromic acid to be described later. In no case was the action of the solution on the metal perfectly normal and uniform. In the presence of oor and 0.25 molar sulphuric acid distinct black coatings formed on the disc; while even at the highest acidity, 5 molar, the disc acquired a browuish discoloration and, ultimately, a minutely spotted appearance. Examined under low magnification these spots were seen to consist of irregular rounded hollows, each containing traces of a brown deposit. As the probable result of these irregularities in the action, we find in all cases that the velocity constants decrease as the experiment progresses, though less rapidly in the more strongly acid solutions. However, the constants for each single experiment, when plotted with time as the other co-ordinate, lie fairly close to a straight line, so that by extrapolating this line back to time zero we obtain a corrected value for the reaction velocity which represents, at least approximately, the rate at which the reaction would proceed under the given conditions if the sources of disturbance were absent. The initial reaction velocity for each experiment, as obtained by such extrapolation, is recorded at the foot of the table. Although, owing to irregularity in the constants, this procedure sometimes fails to give sharp results, these extrapolated values are certainly more accurately and fairly representative of the single experiments, in the present case, than are the average values of their constants, and will therefore be given the preference in comparing nickel with the other metals, CHEMICAL NEWS, } Jan. 5, 1917 Thermo-electric Properties of Fused Metals It should be noted that this process of extrapolation | affords a general method for correcting the observed reaction velocities for the effect of all disturbances which are initially absent but are produced by the progress of the reaction. It will be used in a number of the cases to follow. (To be continued). PROCEEDINGS OF SOCIETIES. PHYSICAL SOCIETY. Ordinary Meeting, November 24, 1916. still hopes that he may be able to overcome these difficulties, while ensuring at the same time that the difference of temperature U, measured by the thermo-couple, is substantially that between the extremities of the wire. He agrees with M.. Owen that the results of Oosterhuis should be confirmed, as well as those of Aalderink, in view of the ex'raordinary conclusions to which they lead; at the same time, he has a very high opinion of the methods adopted at Groningen, and his own results on mercury some time ago were not very different from those of Schoute. In reply to Prof. Eccles, the author has himself felt the difficulty of explaining the essence of the method simply and satisfactorily. Graphs of the distribution of temperature afford little help. What is actually done is explained in a few words in Section 2 of the paper, though no simple proof of the formula is given. A"proof" of the formula = R(C2-C1)/SU is obtained very simply by equating the C2R/SL+CoU/L, when C, is passing from hot to cold, electrical heat produced per second per centimetre-viz., The paper describes how absolute measurements of the direction-viz., C22R/SL-C20 U/L. to that produced when C2 is passing in the opposite This proof was Thomson effect may be made in wires. The theory is omitted not so much because it assumes that o, R, and the fully worked out, and the sources of error likely to arise-temperature gradient are constant everywhere, and ignores especially owing to the smallness of the area of cross-emissivity, as because it neglects thermal conductivity, or section are considered. The method is sensitive, consistent, and very rapid; its ultimate object is to determine the Thomson effect at different temperatures in a number of metals, both rare and base, at the same time, and with the same specimens, finding their thermo-electric powers. The preliminary experiments of this paper, testing the method, are with constantan wires of different lengths, with manganin, and with German silver. Prof. C. V. Boys, F.R.S., President, in the Chair. A PAPER "On the Measurement of the Thomson Effect in DISCUSSION. Mr. F. E. SMITH suggested that the method might have been modified by haying two exactly similar systems arranged in opposite arms of a Wheatstone bridge, so that the current passed from hot to cold in one wire and from cold to hot in the other. Any change in the relative temperatures of the two wires on reversing the current would be indicated by the bridge being thrown out of balance. This seemed preferable to measuring the temperature of a wire by the resistance of another wire wound round it. Mr. D. OWEN thought the method was very satisfactory. Had the author thought of using electrical heating for the hot end in order to get smaller temperature gradients, in view of the high sensibility of the arrangement? He thought the figures of Oosterhuis stood in need of verification. If the author could adapt his method to deal with crystals, such as were employed in wireless detectors, the results would be of very great interest. Dr. R. S. WILLOWS said that it was difficult to see from the equations which Mr. Nettleton had put down on the board whence the energy was derived in cases such as those mentioned in the paper which Mr. Darling was about to read. In some of these cases dE/dT and d2E/dT2 were both zero. It would be useful it the method could be rendered applicable to substances with large temperature coefficients. Prof. W. ECCLES said he had hoped that the author would have explained just what the important points of the method were in a less abstract manner-with the aid, say, of diagrams of the temperature conditions along the wire before and after the current reversal. The AUTHOR, in a written reply, thanks Mr. F. E. Smith for his suggestion, which, however, as regards sensibility, would depend on the value of the temperature coefficient of resistance, and might carry with it additional complications such as those which enter into King's experiments. In reply to Mr. Owen, the use of electrical heaters would simplify temperature coefficient work enormously, but unfortunately there are mechanical difficulties arising out of the facts that the solder fixing the wire must be applied from behind, and that, in order that the resistance of the wire may be measured as a low resistance in situ, the copper must be narrowed down, as shown at K in Fig. 2, leaving a very small bearing surface at N, The author assumes that Joulean and Thomson heat are propagated similarly. In reply to Dr. Willows, the method is equally pplicable to wires of large temperature coefficient. Equation (28) may then be applied, or Equation (2c) if the resistance of the wire be measured directly while under temperature gradient, as suggested in Section 4D. The author has no satisfactory explanation of the energy problems arising out of the researches in Holland or those arising from Mr. Darling's experiments; in the absence of measurements of o and there are few data to go upon. In the case of Mr. Darling's experiments, it must be remembered that though with, say, the bismuth silver couple over the range 300° C.-500° C., both dE/dt and d2E/dT2 are zero, no additional energy or thermo-electric force is manifest. If the law of successive temperature is true with Mr. Darling's materials, a thermocouple composed of molten bismuth and silver with one junction at 300° C. and the other at 400° C. or 500° C., should show no E.M.F. corresponding to zero Peltier effects and equality of Thomson coefficients. A paper "On the Thermo electric Properties of Fused Metals," by C. R. DARLING, A.R.C.S., F.I.C., and A. W. GRACE, was read by the former. One of the authors has for some time been investigating the possibility of using base metal thermo-couples at temperatures above the melting point of one of the constituents. For this purpose it was necessary to determine whether any peculiarities in the thermo-electric behaviour of metals occur at fusion. In the case of lead, tin, zinc, and cadmium there is no perceptible break in the continuity of the curves obtained. In couples containing bismuth, however, several cases were noted in which the E.M.F. remained constant for a wide range of temperature after the fusion of the bismuth. This occurs with silver, aluminium, iron, or nichrom as the other element. Useful applications of this property are discussed. No attempt was made to construct a thermo-electric diagram from the results, as it would be impossible to obtain correct values of dE/dt at all parts of the curves, many of which show small flexures, without making more accurate measurements in the region of such flexures than was practicable. DISCUSSION. Mr, A. CAMPBELL, in a communication which was read by the Secretary, remarked that he had made similar experiments (Proc. Roy. Soc. Edin., 1888) on Wood's metal, an alloy of bismuth melting at 73° C. The results of measurements against iron from 8° C. to 150° C., when reduced to a thermo-electric diagram, gave one straight line up to the melting point, and another straight line, of a different slope, above the melting-point. He disagreed 2 German production in the future. Beautiful specimens of artistic glass, both ancient and modern, were shown, whilst there were severa' interesting and instructive exhibits of glasses illustrating various phenomena met with in glass production. entirely with the authors' remarks on the usual thermo- | scientific glass, there was no necessity to depend on electric diagram. A diagram of the thermo-electric powers was most valuable, even though the lines may not be straight at the extreme temperatures. If anything is to deduced from observed results, the first step is to plot the thermo-electrie powers against temperature. Why the authors give results of tests against a whole series of metals is not clear. A set of tests against one metal would have been sufficient to fix the bismuth curve on the thermo-electric diagram, and all the other results could CHEMICAL NOTICES FROM FOREIGN then have been deduced from the curves of the other metals already determined by more exact methods. The PRESIDENT expressed himself puzzled by the results shown in Fig. 2. Up to the melting point of bismuth the different metals gave with it increasing E.M.F's. At the melting-point, however, discontinuities occurred, and it appeared that if one eliminated bismuth by subtracting the ordinates of one curve from another, discontinuities would also occur, at the melting-point of bismuth, in the properties of the couples obtained by combining the other metals inter alia. This, of course, was not true. Prof. Howe pointed out that there was not a marked discontinuity in the difference of the nickel and copper curves when this was plotted. The President's remarks held, however, in the case of silver with either of the others. Mr. S. W. SMITH pointed out that bismuth was abnormal in that it contracts on melting. Dr. R. S. WILLOWS mentioned that the metals lead, tin, zinc, and cadmium, which had been shown to have no thermo-electric discontinuities at their melting-points, happened to be those which, as Mathiessen had found, formed alloys with one another of which the specific resistance could be deduced from the percentage composition. He suggested that the discrepancy mentioned in the case of iron might possibly be due to the occurrence of some allotropic modification, in which case there was really a change in the substance, and it was unfair to extrapolate the thermo-electric diagram beyond the change point. Mr. DARLING, in reply, said he had no doubt that Mr. Campbell's remarks would hold if one could get out the proper thermo-electric diagram. Owing to the numerous little kinks which occur, very sensitive temperature measurements are required. If really accurate diagrams could be obtained it might then be possible to deduce the properties of any bismuth couple from those of one, as Mr. Campbell suggested. They had tried this in a few cases, however, but did not get good agreement. He did not know whether the peculiarity of bismuth which had been men: tioned was related to the phenomena which they had described. Bismuth was a freak metal in many respects. He was unable at the moment to solve the difficulty raised by the President. Their aim had been, primarily, a practical one, and they had not gone as fully into points of that nature as might have been desired. SOCIETY OF GLASS TECHNOLOGY. THE second meeting of the Society was held on December 14, 1916, in the University of Sheffield, the President (W. F. J. WOOD, B.Sc.) taking the Chair. Dr. H. FRANK HEATH, C.B., of the Advisory Committee of the Privy Council, addressed the meeting. pointing out the good services the Society could render to the nation, and assuring it of the Government's interest and support. SOURCES. NOмT.-All degrees of temperature are Centigrade unless otherwise expressed. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Vol. clxiii., No. 16, October 16, 1916. Chemical Action of Sodium Peroxide on Oxides of Carbon.-C. Zenghelis and Stavros Horsch.-Sodium peroxide reacts energetically with carbon monoxide; a slight rise of temperature occurs and carbonate is formed. With the dioxide the action is more intense and the rise of temperature greater; active free oxygen is evolved. The heat of the second reaction is less than that of the first, and the authors suggest that the second reaction takes place in two stages. In the first phase two CO2 molecules add themselves on to one molecule of Na2O2 to give the percarbonate Na2C2O6, which is then decomposed in the second phase. When sodium peroxide is mixed with any oxidisable substance, such as aluminium, and carbon dioxide is passed over the mixture a violent reaction occurs often ending in an explosion. The action of the CO2 raises the temperature to that of combustion of the substance present, and each molecule of CO2 sets free a molecule of active oxygen. Thus the reaction occurs spontaneously. If magnesium is substituted for aluminium a violent explosion occurs; iron burns without an explosion, the product fuses and finally if a little powdered iron is added Na2FeO, is formed. Zinc and copper both burn if the mixture is heated strongly. Action of Sulphur upon Baryta in Presence of Water. L. Guitteau.-When a mixture of two parts of hydrated baryta, one of sulphur, and 25 of water is boiled a liquid is obtained which is nearly black when hot, becoming orange-red on cooling. The solution when allowed to stand decomposes slowly, giving hydrated hyposulphite of barium, and sulphur, with liberation of sulphuretted hydrogen. But if it is evaporated by heating, red prisms of barium tetrasulphide (BaS4H2O) mixed with sulphur and hyposulphite are obtained, while the orange mother-liquor appears to contain the persulphide BaS,. This compound is unstable and readily decomposes as follows :3 BaS5+ 3H2O= BaS4+S2O3Ba+3H2S+S. Crystalline Liquids obtained by Evaporating a Solution.-P. Gaubert.-When a solution of anisal-pamidoazotoluol in ether, benzene, &c., is evaporated on a piece of glass a birefringent liquid phase is produced, which is green by reflection. The green colour is due to the existence of very unstable liquid crystals, which are optically negative. When the liquid solidifies it gives rise to two unstable forms differing from that obtained from the anisotropic liquid produced by fusion. The author has cinnamate, p-azooxyanisol, esters of cholesterine, and similarly studied liquid crystals from ethyl anisalaminoactive amyl cyanbenzalal aminocinnamate. MEETINGS FOR THE WEEK. The remarkable developments that have taken place in the glass industry during the last two years were emphasised by an exhibition of various types of glass including (a) Scientific Ware, (b) Optical Glass, (c) Artistic Glass, (d) Miscellaneous Exhibits. Many TUESDAY, 9th.-Royal Institution, 3. "firms and private individuals sent collections for exhibition, and it was apparent that in chemical ware and other (Christmas Lectures, adapted to a juvenile auditory). "The Human Machine which all must Work," by Prof. Arthur Keith, M D., F.R S., &c. SOCIETY THE ALCHEMICAL was formed in 1912 for the study of the early history of Chemistry and the works and THE JOURNAL OF THE ALCHEMICAL SOCIETY, Edited by H. STANLEY REDGROVE, B.Sc., F.C.S. (Author of "Alchemy: Ancient and Reprints of the 1913 Address of the Honorary President, Prof. JOHN FERGUSON, LL.D., &c., on "Some English Alchemical Books," may be obtained from the Publishers at 1s. net per copy. The Annual Subscription to the Society is 12s. 6d. Members receive the Journal gratis, and those desirous of doing so, may receive Les Nouveaux Horizons, the official publication of La Société Alchimique de France, free of charge, except postage (6d. per annum). For further particulars apply to the Honorary Secretary, Mr. SIJIL ABDUL-ALI, 26, Bramshill Gardens, Dartmouth Park, London, N.W. |