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small flat-flame burners, and then gives a light of 240 candles when consumed at the rate of five feet per hour. It is claimed that calcium carbide can be produced in this way for about $20 per ton. Since a ton will yield about 11,000 cubic feet of gas, the cost at this rate would be about $1.60 per thousand cubic feet, deducting the value of bye-products. In illuminating value, it would be equivalent to ordinary coal gas at about ten or twelve cents per thousand. Moreover, since acetylene is the starting point for a multitude of organic syntheses, this cheap production is of great importance in chemical industry.- Nature, li, 303, January, 1895.

G. F. B. 7. Theoretical Chemistry from the Standpoint of Avogadro's rule and Thermodynamics. By Prof. WALTER NERNST, Ph.D., of the University of Göttingen. Translated by Prof. CHARLES SKEELE PALMER, PH.D., of the University of Colorado, 8vo, pp. xxvi, 697. London and New York, 1895 (Macmillan & Co.), $5. -Dr. Nernst is well known as one of the leaders of the new School of Physical Chemists. His papers upon subjects within this domain have received marked attention and have made him an authority in this branch of chemistry. A book from his pen, like the one now before us, therefore, cannot fail to be of great service in advancing chemical science and will, no doubt, be warmly welcomed by his co-laborers in every land. It is divided into four principal divisions or books, preceded by an introduction upon matter and energy and their relations. The first book treats of the universal properties of matter, such as the gaseous, the liquid and the solid states of aggregation, the physical mixture and dilute solutions. The second book considers the atom and the molecule, taking up successively the atomic theory, the kinetic theory of the molecule, the determination of molecular weight, the constitution of the molecule, the relation between physical properties and molecular structure, the dissociation of gases and electrolytic dissociation, the physical properties of salt solutions, and the absolute size of molecules. Book third discusses the transformation of matter, being the first part of the doctrine of affinity; its chapters being upon the laws of chemical mass-action, the chemical statics of homogeneous and heterogeneous systems, chemical equilibrium in salt solutions and chemical kinetics. Book fourth is devoted to the transformation of energy, being the second part of the doctrine of affinity; its first five chapters treating of thermochemistry and its last two of electrochemistry and photochemistry respectively. Two valuable appendices complete the work. One, edited by Dr. Nernst himself, contains important matter which has appeared since the publication of the German edition. The other, edited by Dr. Kaiser, is a synchronistic comparison of the chief periodicals bearing on this department of chemistry. From this résumé will appear at once not only how wide is the range of subjects treated in this volume, but also how clear and logical is the order in which they are taken up. Dr. Nernst everywhere speaks with

the authority of a master of his subject. So that his book, notwithstanding the treatises of Ostwald and others on Physical Chemistry, seems to lis, in the excellence of its arrangement, the clearness of its style and the thoroughness of its subject-matter, to be the best book of its kind which has yet appeared. Dr. Palmer deserves especial thanks for putting the book so admirably into its English dress. Typographically also, the book is a credit to its publishers.

G. F. B. 8. Qualitative Chemical Analysis of Inorganic Substances, as practiced in Georgetown College, D. C. Short 410, pp. 61. New York, 1894 (American Book Company).—This book consists of a series of tables for qualitative analysis, divided into four sets. The first is on Basic Analysis, the second on Acid Analysis, the third on Preliminary Examination, and the fourth on Solution and on Special treatment. Though in the main following well established authorities, yet there is some originality of arrangement and some satisfactory explanatory matter added to the tables. The book appears to have been prepared with considerable care.

G. F. B. 9. Double refraction of Electric waves.--K. Mack by interposing pieces of wood between Hertz's well known parabolic reflectors, the axes of which are inclined to each other, has shown that electric waves can be doubly refracted. Most specimens of wood have a different structure along the direction of the fibres from that perpendicular to this direction, and accordingly resemble in this respect doubly refracting crystals possessing a structure parallel to their optic axis different from that at right angles to this axis. When pieces of wood about 20cm thick were interposed on the line joining the foci of the mirrors, clear evidence of the doubly refracting properties of the wood could be shown by the appearance or disappearance of the spark in the micrometer connected with the receiving mirror. - Ann. cler Physik. und Chemie, No. 2, 1895, pp. 342–351.

J. T. 10. National Academy of Sciences on Electrical Measurement. -The standard specifications for the practical application of the definitions of the electrical units, ampere and volt, referred to in the act of Congress of July 12, 1894, quoted in the last number of this Journal (p. 236), are given below; they are taken from Miscellaneous Document, No. 115, of the Senate of the United States. These specifications were approved by all the members of the committee named, of which Prof. H. A. Rowland was the chairman, and were unavimously adopted by the Academy at a special meeting held in New York on the 9th of February, 1895.

Specifications for the practical application of the definitions

of the Ampere and Volt.

SPECIFICATION A.The Ampere. In employing the silver voltameter to measure currents of about one ampere, the following arrangements shall be adopted :

The kathode on which the silver is to be deposited shall take the form of a platinum bowl not less than 10 centimeters in diameter, and from 4 to 5 centimeters in depth.

The anode shall be a disc or plate of pure silver some 30 square centimeters in area and 2 or 3 millimeters in thickness.

This shall be supported horizontally in the liquid near the top of the solution by a silver rod riveted through its center. To prevent the disintegrated silver which is formed on the anode from falling upon the kathode, the anode shall be wrapped around with pure filter paper, secured at the back by suitable folding.

The liquid shall consist of a neutral solution of pure silver nitrate, containing about 15 parts by weight of the nitrate to 85 parts of water.

The resistance of the voltameter changes somewhat as the current passes. To prevent these changes having too great an effect on the current, some resistance besides that of the voltameter should be inserted in the circuit. The total metallic resistance of the circuit should not be less than 10 ohms.

Method of Making a Measurement. The platinum bowl is to be washed consecutively with nitric acid, distilled water and absolute alcohol; it is then to be dried at 160° C., and left to cool in a desiccator. When thoroughly cool it is to be weighed carefully.

It is to be nearly filled with the solution and connected to the rest of the circuit by being placed on a clean insulated copper support to which a binding screw is attached.

The anode is then to be immersed in the solution so as to be well covered by it and supported in that position; the connections to the rest of the circuit are then to be made.

Contact is to be made at the key, noting the time. The current is to be allowed to pass for not less than halt an hour, and the time of breaking contact observed.

The solution is now to be removed from the bowl and the deposit washed with distilled water and left to soak for at least six hours. It is then to be riused successively with distilled water and absolute alcoliol and dried in a hot-air bath at a temperature of about 160° C. Alter cooling in a desiccator it is to be weighed again. The gain in mass gives the silver deposited.

To find the time average of the current in amperes, this mass, expressed in grams, must be divided by the number of seconds during which ihe current has passed and by 0:001118.

In determining the constant of an instrument by this method, the current should be kept as nearly uniform as possible and the readings of the instrument observed at frequent intervals of time. These observations give a curve from which the reading corresponding to the mean current (time-average of the current) can be found. The current, as calculated from the voltameter results, corresponds to this reading.

The current used in this experiment must be obtained from a battery and not from a dynamo, especially when the instrument to be calibrated is an electrodynamometer.

SPECIFICATION B.The Volt. Definition and Properties of the Cell. The cell has for its positive electrode, mercury, and for its negative electrode, amalgamated zinc; the electrolyte consists of a saturated solution of zinc sulphate and mercurous sulphate. The electromotive force is 1:434 volts at 15° C., and between 10° C. and 25° C., by the increase of 1° C. in temperature, the electromotive force decreases by .00115 of a volt.

1. Preparation of the Mercury. To secure purity it should be first treated with acid in the usual manner and subsequently distilled in vacuo.

2. Preparation of the Zinc Amalgam.—The zinc designated in commerce as “commercially pure” can be used without further preparation. For the preparation of the amalgam one part by weight of zinc is to be added to nine (9) parts by weight of mercury and both are to be heated in a porcelain dish at 100° C. with moderate stirring until the zinc has been fully dissolved in the mercury.

3. Preparation of the Mercurous Sulphate. Take mercurous sulphate, purchased as pure, mix with it a small quantity of pure mercury and wash the whole thoroughly with cold distilled water by agitation in a bottle; drain off the water and repeat the process at least twice. After the last washing, drain off as much of the water as possible. (For further details of purification, See Note A.)

4. Préparation of the Zinc Sulphate Solution. Prepare a neutral saturated solution of pure re-crystallized zinc sulphate, free from iron, by mixing distilled water with nearly twice its weight of crystals of pure zinc sulphate and adding zinc oxide in the proportion of about 2 per cent, by weight of the zinc sulphate crystals to neutralize any free acid. The crystals should be dissolved with the aid of gentle heat, but the temperature to which the solution is raised must not exceed 30° C. Mercurous sulphate, treated as described in 3, shall be added in the proportion of about 12 per cent by weight of the zinc sulphate crystals to neutralize the free zinc oxide remaining, and then the solution filtered, while still warm, into a stock bottle. Crystals should form as it cools.

5. Preparation of the Mercurous Sulphate and Zinc Sulphate Paste. For making the paste, two or three parts by weight of mercurous sulphate are to be added to one by weight of mercury. If the sulphate be dry, it is to be mixed with a paste consisting of zinc sulphate crystals and a concentrated zinc sulphate solution, so that the whole constitutes a stiff mass, which is permeated throughout by zinc sulphate crystals and globules of mercury. If the sulphate, however, be moist, only zinc sulphate crystals are to be added ; care must, however, be taken that these occur in excess and are not dissolved after continued standing. The mercury must, in this case also, permeate the paste in little globules. It is advantageous to crush the zinc sulphate crystals before using, since the paste can then be better manipulated.

To set up the Cell. The containing glass vessel, represented in the accompanying figure, shall consist of two limbs closed at bottom and joined above to a common neck fitted with a ground glass stopper. The diameter of the limbs should be at least 2cms and their length at least 3cms. The neck should be not less than 1.5cms in diameter. At the bottom of each limb a platinum wire of about 0•4mm diameter is sealed through the glass.

To set up the cell, place in one limb pure mercury and in the other hot liquid amalgam, containing 90 parts mercury and 10 parts zinc. The platinum wires at the bottom must be com

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