SCIENTIFIC INTELLIGENCE.

I. CHEMISTRY AND PHYSICS.

1. On the Vapor-density of Aluminum chloride.-The experiments of Nilson and Pettersson (Zeitschr. phys. Chem., i, 459) seemed to show that aluminum chloride when heated in an atmosphere of carbon dioxide gave, at a temperature of about 835°, a vapor-density corresponding to the formula AICI,; and this without evidence of decomposition, although above 935° the platinum vessel was attacked. FRIEDEL and CRAFTS have pointed out that exact results are obtained with V. Meyer's method (which was the one used by Nilson and Pettersson) only when there is no diffusion of the vapor into the air of the apparatus. And they have therefore re-determined the vapor-density of aluminum chloride by the method of Dumas, taking great care to obtain and to maintain the substance perfectly anhydrous. The aluminum chloride was obtained by sublimation in large, colorless and comparatively non-hygroscopic crystals, which though volatilizing directly without fusion at ordinary pressures, melt at about 186° under a pressure of 2.5 atmospheres. The vaporpressure of this substance was found to be 252.1 mm. at 167.8° 3114 mm. at 170·4°; 3165 mm. at 171.9°; 430.7 mm. at 175·7° 755.4 mm. at 182.7°; 1793-4 mm. at 204.2°; 2016·1 at 207·5°; and 2277.5 mm. at 213.0°. The temperatures at which the vapordensities were determined were 218°, 263°, 306°, 357°, 390°, 398°, 400°, 415°, 429° and 433°; and the results agreed closely with the density 9.24, the value corresponding to the formula Al,CI; thus confirming the earlier results of Deville and Troost. Since the lowest temperature at which Nilson and Pettersson operated was 440°, it may be that the lower values obtained by them are due to a dissociation of the molecule Al,Cl, into (AIČI ̧), analogous to that of iodine, or into Al,Cl, and Ĉl, as in the case of ferric chloride. The authors' experiments prove, however, that aluminum chloride becomes a perfect gas at 218°, or 35 degrees above its boiling point; and that the density of this vapor is sensibly the same up to 400°. Hence they conclude that the formula of this substance is Al,Cl; a conclusion in agreement with the determinations of Louise and de Roux of the vapor-densities of aluminum methide and aluminum ethide.-C. R., cvi, 1764; J. Chem. Soc., liv, 1040, Oct., 1888.

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G. F. B.

2. On Freezing mixtures containing solid Carbon dioxide.CAILLETET and COLARDEAU have determined the temperature of solid carbon dioxide, alone as well as when mixed with other suitable substances, in air and in vacuo. For this purpose they used a thermo-electric couple which had been calibrated by comparison with a hydrogen thermometer. The carbon dioxide alone, either compressed or porous, when exposed to the air, had a temperature -60° and when in a vacuum over potassium hydrate,

-76°. When mixed with ether, the dioxide had a temperature of -77° in air and of 103° in a vacuum. Liquid carbon dioxide solidifies in such a mixture. On the addition of the solid dioxide to the ether it at first dissolves, and after a time bubbles of gas are evolved. On continuing to add the dioxide the liquid becomes saturated and opalescent, the temperature falling until the instant of saturation is reached, when no farther fall of temperature occurs on adding more dioxide. Hence it would appear that the effect of the ether is due simply to its dissolving the dioxide. Other solvents may be used. Methyl chloride gives -82°; sulphurous oxide -82°; amyl acetate -78°; phosphorous chloride —76°; .alcohol -72°; and ethylene chloride -60°. When the mixture with methyl chloride or sulphurous oxide is placed in a vacuum the temperature is lowered to a point at which the solvent solidifies and then no farther reduction takes place. The temperature thus obtained with methyl chloride is

106°. A mixture with chloroform solidified at the ordinary pressure at -77°.-C. R., cvi, 1631; J. Chem. Soc., liv, 1025, Oct., 1888.

G. F. B.

3. On the Determination of the Heat of Combustion of Coal. -Scheurer-KesTNER has analyzed and has also determined the heat of combustion of twenty-one samples of coal from the north of France, by direct experiment, and has compared the results with those calculated from the composition of the coals. The coal in small fragments was burned in a rapid current of moist oxygen in a Favre and Silbermann's calorimeter; the results being corrected by subtracting from the heat of combustion actually observed with the moist gas, and consequently with complete condensation of the water formed, the number of calories equivalent to this condensation. Since the combustion of hydrogen gives 34,500 or 29,088 calories according as the water formed is condensed or is in the state of vapor, the difference, or 5413 calories, multiplied by the content of the coal in hydrogen, represents the number of calories to be subtracted from the observed heat of combustion. The values of the heats of combustion actually obtained do not agree with the values calculated from the composition, being sometimes greater than the sum of the heats of combustion of the constituents and sometimes less. Cornut has proposed a formula for calculation based on the assumption that while solid carbon evolves 8080 calories, the heat of combustion of carbon in the state of vapor is 11,214 calories. But the calculations founded on this formula of Cornut, while giving results somewhat closer to those actually observed in some cases, are in other cases so far from the truth as to destroy confidence in it. The formula of Dulong is even less satisfactory. No explanation is offered as to the cause of these discrepant results, but they seem to establish the important fact that coal has been formed at least in part by endothermic reactions. The general results give between 8340 and 9257 calories, the mean values lying between 8400 and 8800 calories.-Ann. Chim. Phys., VI, xv, 262, Oct., 1888. J. Chem. Soc., liv, 774, Aug., 1888.

G. F. B.

4. On the Wave-length of the Double red line in the spectrum of Potassium.-By means of a Rutherfurd grating ruled on glass, and the electric arc, DESLANDRES has succeeded in measuring the wave-length of the two components of the double potassium line in the red, known as Ka. He finds for the stronger of the two lines the value 7663.0 ten-millionths of a millimeter, and for the weaker line the value 7696.3 ten-millionths; the value for D being taken at 5888.9. This agrees with the value 7680·0 found by Mascart for the group, that of D being 5888′0.— C. R., cvi, 739; J. Chem. Soc., liv, 637, July, 1888.

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G. F. B.

5. Electrical discharges in gases and flames.-The observation of Hertz upon the effect of the ultra violet rays upon electrical discharges has awakened wide spread interest in Germany. Among other workers, E. WIEDEMANN and H. EBERT have repeated and confirmed Hertz's results. They have also investigated the effect of ultra violet rays upon electrical discharges which are taken in various media. The source of light was a Schuckert's electric are light. It was found that the effect of the ultra violet rays was greatest when the electrodes between which the electrical discharge passed were of platinum. A telephone was intercalated in the circuit and the character of the discharge when the electrodes were in the violet rays and when they were not could be readily distinguished. A glass plate which allowed the violet rays to pass, but absorbed the ultra violet, immediately caused the phenomenon to disappear; thus it was shown that the ultra violet rays alone were effective. The effect varied with the character of the electrodes, being greatest with platinum. And then in the following order: zinc, copper, iron, aluminum, palladium, silver. When the discharge was taken from the surface of a liquid, the greatest effect was always obtained when the liquid was capable of absorbing the ultra violet rays. The authors believe that the phenomena can be attributed to the selective absorption for ultra violet rays of the surfaces between which the electrical discharges pass. The short wave-lengths set the molecules on these surfaces into vibration and thus aid the disruptive effect which is seen in the discharge. The phenomenon was also investigated in Geissler tubes and with low pressures. When the electrical discharge grew rich in ultra violet rays, the effects of similiar rays from the arc lamp were less noticeable. The discharge was also taken between points placed in flames which were colored. by various salts. These salts changed the character of the discharge greatly, as was evidenced by the noise in a telephone connected with one of the electrodes. The greatest effect was obtained from potash and from the magnesium salts, thus affording another instance of the effect of ultra violet rays affecting the electrodes by selective absorption.-Ann. der Physik und Chemie, No. 10, 1888, pp. 209-264.

J. T.

6. Electrodynamic effect produced by the movement of a dielectric in an electrical field.-W. C. RÖNTGEN revolved a glass or vulcanite disc between two horizontal plates of a condenser, one

of which was connected with the earth, the other with the source of electricity. Above the upper condenser plate was hung a very sensitive magnetic system. The direction of the magnetic needles was perpendicular to a radius of the revolving disc, and their middle point was near the edge of the disc. The deviation of this system was measured by a mirror, telescope and scale. The author concludes, after discussing the relation of the effects observed to those obtained by Rowland and by others, that a small electrodynamic effect can be noticed, when a dielectric is moved in a homogeneous electrical field.-Ann. der Physik und Chemie, No. 10, 1888, pp. 264–270.

J. T.

7. Light and Electricity.-LORD RAYLEIGH (B. A., 1988) has been endeavoring to discover if an electric current flowing through an electrolyte causes the velocity of light to vary through the liquid. He experimented with dilute sulphuric acid. The result was negative within the range of the experiment, which was extremely delicate. In H2SO, diluted, one ampère per square centimeter does not alter the velocity of light by one part in thirteen millions, or by fifteen meters per second.-Nature, Oct. 4, 1888, p. 555.

J. T.

8. The energy stored in permanent strains; by C. BARUS. (Communicated). Apropos of certain strain experiments of Wassmuth, an account of which has just reached me in the Beiblätter (No. 9, p. 648, 1888), I desire to advert to somewhat similar results which I have in hand. I brought a measured amount of work to bear on soft metallic wires, and by deducting from this the energy thermally dissipated (measured in a way essentially like that of Wassmuth), I was able to express definitely the energy potentialized in effecting given changes of molecular configuration. In this respect my work and purposes are distinct from Wassmuth's. Necessarily operating on soft metal, I find that the values for the maxima of energy stored under given conditions differ so largely in different metals, that I am justified in treating them as molecular data of importance.

II. GEOLOGY AND MINERALOGY.

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1. International Congress of Geology.-The members of the "Provisional Committee" appointed at the Congress in London, with reference to preparations for the next meeting of the Congress at Philadelphia, whose names are mentioned on page 389, met at New Haven, on Thursday, the 15th of November. were present except Dr. T. Sterry Hunt. By vote twenty-four members of the permanent or organizing committee were appointed, as follows: C. A. Ashburner, J. C. Branner, T. C. Chamberlin, G. H. Cook, J. D. Dana, W. M. Davis, C. E. Dutton, G. K. Gilbert, James Hall, A. Heilprin, C. H. Hitchcock, Joseph LeConte, J. Leidy, J. P. Lesley, O. C. Marsh, J. S. Newberry, J. W. Powell, J. R. Procter, N. S. Shaler, J. J. Stevenson, C. D. Walcott, R. P. Whitfield, H. S. Williams,

Alexander Winchell. The committee has power to add to its number. Dr. J. S. Newberry was appointed temporary chairWith this action, the duties of the provisional committee ended. The first meeting of the permanent committee will be held in Washington in the month of April.

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2. American Report to the International Congress of Geologists at the meeting in London commencing September 17, 1888.—This Report, as the title-page states, is made up of "Reports of the American Sub-committees appointed by the American Committee from its own members, assisted by associates, and is "printed by order of the Committee. Editor, Persifor Frazer." It contains valuable papers on American stratigraphical geology prepared chiefly by the Chairmen or Reporters" of several Sub-committees, and interesting reading as the personal opinions on various questions, which were gathered in by the assiduous Secretary and some of the "Reporters" through epistolary canvassing. But on controverted points it is a "majority" report of the Committee and of its several Sub-committees, and a minority report as regards American geologists. The canvassing gathered opinions, but not the final views which free discussion among the geologists of the country would have evoked. Moreover the methods of the Committee tended to suppress discussion even in the Sub-committees.

The Preface of the published Report states that "all geologists were invited to meet the American Committee in Albany during its session there (April 6th, 1887), in order to aid it in arriving at a correct view of American opinion." Such a call was published in volume xxxiii of this Journal (1887); but the notice of the next meeting at Philadelphia, communicated to the same volume by the Secretary, shows that it failed of the object announced.

At the only meeting attended by the writer, that of January last at New Haven--not then resuming active membership, as the published Report states in its Preface, but taking my first experience in membership after receiving my first notice that I was a member, the chairman,-Dr. T. Sterry Hunt, opened the session in the morning by announcing that five-minute speeches. only would be allowed in discussions, and no replies, thus showing at the outset that full and fair consideration of questions was not to be permitted.

During the day the reports of some of the Sub-committees were read and passed, but no opportunity was allowed for the discussion of any of the propositions to the International Congress which they contained. Before the meeting closed, a vote was passed by which "the Reporters of the Sub-committees respectively were made sole and final judges of the manner in which communications received from other geologists should be used." At the same time" the reports on the Archæan, Devonic, Carbonic, Mesozoic and marine Cenozoic " were declared adopted and ready for printing, and those "on the Lower Paleozoic and In