[CONTRIBUTIONFROM THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY.]
REVIEW OF AMERICAN CHEMICAL RESEARCH. VOL. V. No. 6. ARTHER A. NOYES,Editor ; HENRY P. TALBOT, Associate Editor. REVIEWERS:Analytical Chemistry, H. P. Talbot and W. H. Walker; Biological Chemistry, A. G. Woodman ; Carbohydrates, G. W. Rolfe ; General Chemistry, A. A . Noyes ; Geological and Mineralogical Chemistry, W. 0. Crosby ; Inorganic Chemistry, Henry Fay ; Metallurgical Chemistry and Assaying, H. 0. Hofman ; Organic Chemistry, J. F. Norris ; Physical Chemistry, H. M. Goodwin ; Sanitary Chemistry, E. H. Richards ; Technical Chemistry, A. H. Gill aod F. H. Thorp.
GENERAL AND PHYSICAL CHEMISTRY. H. M. GOODWIN,REVIEWER.
A New Determination of t h e Electrochemical Equivalent of Silver. BY GEO. W. PATTFRSON, JK., A N D KARL,E. GUTHE. Phys. Rev., 7, 258--282.-The discrepancy between the values of the mechanical equivalent of heat as determined by the direct and by the electrical method, led the authors to believe it might be due to errors in the standards used, in particular in thevalue of the ampere. A redetermination of the electrochemical equivalent was therefore undertaken. T h e investigation was carried out with great care in all its details, and is of particular value, as it does not involve either the acceleration due to gravity or the horizontal intensity of the earth’s magnetism. T h e method consists essentially in balancing the electrodynamic action of the coils of a primary electrodynamometer (of special design) against the torsional moment of a phosphor-bronze wire. T h e measurements involved are only those of mass and time, and the authors regard their results as accurate to one part in five thousand. A silver voltameter .was used with the usual precautions. T h e final value-the mean of four determinations-of the electrochemical equivalent of silver was found to be o.oo11192+ gram per ampere per second. This value is about per cent. greater than that generally accepted. It agrees with the average value of Pellat and Potier, and is almost identical with that given by Kahle (0.001 I 193 gram), Assuming the above value, the discrepancy between Griffith’s and Rowland’s value for the mechanical equivalent of heat disappears.
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Review of Amen’can Chemical Research.
On the Density of Ice. BY EDWARD L. NICHOLS. Plys. Rev., 8 , 21-37.-The first part of the paper contains a critical review of previous determinations of this constant, and brings out the fact that although the results of individual observers check well among themselves the agreement is not satisfactory when the results of different observers are compared. I t seemed not unlikely that the nature of the ice itself was the cause of the discrepancy. To settle this point and particularly to determine the density of ice as formed in the ice calorimeter, the author made a number of careful determinations of ice from various sources, and found that the density is not the same under all circumstances, a s is shown by the following values (referred to water a t 0’) : Ice frozen with carbon dioxide and ether, 0.91615 f o.oooog ; natural icicles, 0.g1807 I+ 0.00004 ; newly cut pond ice,o.g1804; pond ice one year old, 0.91644. On the Dielectric Constant and Electrical Conductivity of Liquid Ammonia. BY H. M. GOODWINA N D M . DE KAY THOMPSON, JR. Phys. Rev., 8,38-48.--The di-electric constant of liquid ammonia was measured by Drude’s method of electrical resonance ; and values varying from 2 1 to 23, according to the preparation of the ammonia, were obtained a t its boiling-point (-34’ C.) under atmospheric pressure. This value, which is very low7 compared with that of water, would seem to indicate that liquid ammonia is an exception to Nernst’s Lawv,since reasoning from the experiments on the electricalconductivity of liquid animonia solutions made by Cady and the authors, animonia is probably a solvent of high dissociating power. ,4 convenient method for measuring the conductivity of this solvent is described and results on solutions of silver nitrate are given. On the Osmotic Pressure of Certain Ether Solutions and Its Relation to Boyle-van’t Hoff’s Law. BY H. M. GOODWIN AND GEO. K. BURGESS. Phys. Rev., 7 , 171-187.--The lowering of the vapor-pressure of solutions of naphthalene, benzophenone, and diphenylamine in ether was measured directly, by causing the solutions and the pure solvent to boil at constant temperature. Equality of temperatures was indicated by a platinum resistance thermometer placed in the boiling flasks, and pressures were measured on a mercury manometer by means of a cathetometer. From the observed vapor-pressure lowerings the corresponding osmotic pressures, P, of the solutions were computed by an exact formula which took into account the deviations of the pressure of the solvent vapor from Boyle’s Law. T h e concentration 6f the solutions was reduced to mols per liter by means of specific gravity determinations, so that a direct investigation of the relation PV = RT could be made. I t was found that the product P V instead of being constant, diminished in all cases with in-
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creasing concentration. The form of the P V curves varied with the solute, and was in general similar to the well-known curves exhibited by imperfect gases under high pressure. It would seem that each solute therefore deviates from the Boyle-van ’t Hoff Law in much the same way that most gases deviate from the ideal gas laws, each substance having its own characteristic “condition-equation.” Azobenzene investigated by Noyes and Abbot follows the perfect gas laws more nearly than any of the other substances thus far investigated.
ANALYTICAL CHEMISTRY. U L T I M A T E ANALYSIS. H. P. TALBOT. REVIEWER.
The Determination of Potash asPerchlorate. BYF. S. SHIVER. areview of the various methodsproposed for the determination of potassium, the author presents the results of experiments from which he concludes that the method of Caspari (Ztschr. angew. Chew., r893, 68), as modified by Kreider (‘4m.J. Sci., 149, 443), will yield results equal in accuracy to those obtained by the use of platinum, in the case of mixtures free from other bases and non-volatile acids, and that it seems likely to prove satisfactory in the presence of these substances. Four procedures for the preparation of perchloric acid, those of Schlosing and of Porrey (both to be found in Grandeau’s Trait6 d’Analyse des Mafieyes agm’coles, I , 88-91 ) , Caspari (Ztschr. angew. Chem., 1893,68), and Kreider (Loc. c i t . ) , are briefly describe;. A New Method for the Determination of Zinc. BY A . C. LANGMUIR. J . A m . Chem. Sot., 21, r15-118.--In the method proposed, the zinc precipitate (sulphide) is dissolved in nitric acid, the solution evaporated, and the zinc converted to oxide by ignition. I t is recommended that the zinc be thrown down from a dilute solution, and that the precipitate be dissolved without washing, to avoid the usual difficulties at this point, and that the impurities in the ignited oxide be determined and deducted from the apparent weight. In the analysis of many alloys containing zinc, the solution from which the copper and lead have been removed by electrolysis, may be directly evaporated and the residue strongly ignited. The Determination of Arsenic in Glycerine. BY A. C. LANGMUIR. J . Am. Chem. Soc., 21, 133-136.-The glycerine is destroyed by evaporation with sulphuric and nitric acids, transferred to a Marsh generator, and the gas passed through a hard glass tube, constricted as usual, with a piece of filter-paper
J . A m . Chem. Sot., 21,33-42.-Following
