by depositing lead by means of zinc from a solution of lead acetate, and heating it in a vacuum, that finely divided lead absorbs about 0.206 of its volume of hydrogen. The absorption of air by the accumulator plates would be too small to have an appreciable effect on the E.M.F.

The author, however, found it impossible to obtain any trustworthy results from a cell containing platinum instead of copper, owing to the dependence of the E.M.F. on the amount of air absorbed by the platinum. G. W. T.

Determination of the Specific Inductive Capacities of Conducting Liquids. By E. COHN and L. ARONS (Ann. Phys. Chem. [2], 33, 13-31). In a previous memoir (ibid. [2], 28, 454), the authors gave a means of determining the specific inductive capacity of a conducting liquid founded on the result obtained by, them that the dielectric polarisation and conduction are mutually independent. In the former experiments, the highest conductivity did not exceed 45 × 10-13 in terms of mercury, and the values of the sp. ind. cap. were found to be of much the same magnitude as for good insulators, being in every case less than 5. In the present paper, liquids of higher conductivity are considered, and this made it necessary to devise a new method, as the former one, depending on observations of the rate of leakage of an electrostatic charge, would have required the observations of intervals of time considerably less than the millionth of a second.

The method used for the present inquiry is a modification of Silow's (this Journal, 1876, ii, 267), founded on the principle that when a system of conductors immersed in a homogeneous medium is maintained at a constant potential, the work done against electrical forces, in effecting a given change of configuration, is proportional to the sp. ind. cap. of the medium. The needle and one pair of quadrants of an electrometer were joined to one extremity of the secondary of an induction coil, and the remaining pair to the other extremity. Readings were then taken alternately with the liquid and with air only in the electrometer. By this means measurements could be obtained for liquids having a conductivity as high as 16 × 10−1o, or about 3400 times the highest conductivity in the former series. Calling K the sp. ind. cap., and k the conductivity, it was found that for distilled water K = 76, whilst k varied from 34 x 10-10 to 16 x 10-10, so that an increase of conductivity to about five times its original value had no perceptible effect on the sp. ind. cap. For ethyl alcohol containing 2 per cent. of water, K 26.5, and when, by the addition of traces of ammonium chloride, the conductivity was increased from 23 × 10-10 to 12 x 10-10, the value of K remained sensibly constant.

=

For amyl alcohol the values obtained were K = 15 and k = 0·16 × 10-10. When successive quantities of ethyl alcohol were added to pure xylene, both K and k increased, but the latter at first much more rapidly than the former, the change of k from less than 10 to 0.03 being accompanied only by a change of K from 2:36 to

3.08.

For these substances, Maxwell's law connecting sp. ind. cap.

and index of refraction does not hold even approximately, the deviation from the law being very much greater than even in the case of glass and the fatty oils. The author suggests that it would be of interest to investigate the sp. ind. caps. of aqueous and alcoholic solutions of various salts to as high a degree of concentration as possible, and also to determine the same constant for as many welldefined chemical compounds as possible, in order to see if it may not be possible to find some law connecting the sp. ind. cap. of a substance with its chemical constitution. G. W. T.

Conductivity and Specific Inductive Capacity. By E. COHN and L. ARONS (Ann. Phys. Chem. [2], 33, 31-32).—In this note the authors state that the numbers 2-23 and 4:43 given by them in the paper referred to (ibid. [2], 28, 454) as the specific inductive capacities of xylene and castor oil respectively are, according to their later researches, too small, and should be 2:36 and 4-82 respectively.

G. W. T.

Specific Inductive Capacity of Liquids. By F. TOMASZEWSKI (Ann. Phys. Chem. [2], 33, 33-42).-The principal object of this investigation was to obtain measurements of the specific inductive capacities of certain liquids in order to determine, if possible, some relation between the value of this constant and the chemical constitution of the liquid, which curiously enough was one of the desiderata suggested by Cohn and Arons (preceding Abstracts).

There were two questions which presented themselves for solution : (1) The influence of the number of atoms in a molecule, requiring determinations for isomeric, homologous, and metameric compounds. (2) The effect of introducing a fresh element into the molecule, requiring determinations for non-homologous compounds.

The experiments were carried out by Silow's method slightly modified, and the charges were obtained from a battery of 40 zinc-copperwater cells.

The principal results obtained are given below, K being the specific inductive capacity, and u the index of refraction for infinite wavelength.

The specific inductive capacities of isomeric compounds are, therefore, not equal.

Where M is the molecular weight and d the density, it was found that the quantity M(n - 1)/d, or the molecular refraction, was sensibly constant for the isomeric series, as also were the quantities M(K1)/d and M(K 1)/d. The specific inductive capacity of homologous compounds is seen from the second table to increase with the number of atoms. Maxwell's relation d = K is only approximately true, as is clear from the tables given. G. W. T.

Electric Discharge through Gases. By A. SCHUSTER (Proc. Roy. Soc., 42, 371-379).—A glass vessel is divided into two compartments by means of a metal plate nearly reaching to the sides and connected to earth. In one compartment charged gold leaves were placed, in the other electrodes through which discharges were passed from an induction coil. No effect was observed at the atmospheric pressure, but at 43 mm. pressure the leaves slowly collapsed. In another experiment, sparks from a Voss machine were passed at the atmospheric pressure between points or spheres in the neighbourhood of charged balls. When the electrodes were similar, whether points or spheres, the balls collapsed when electrified positively, but when one electrode is a sphere and the other a point, the balls collapse if their electrification is of opposite sign to that of the point. Finally, the author observes that in a partial vacuum incompletely divided into two compartments by a metal screen connected to earth, a continuous discharge between electrodes in one compartment renders it possible to send a current between electrodes in the other compartment with an indefinitely small electromotive force. In one case, a current of 0.008 ampère through the main electrodes enabled an E.M.F. of one-fourth volt to send a current through the auxiliary electrodes. The intensity of the auxiliary current is greater the greater the main discharge and the reduction of pressure; it increases less rapidly than the electromotive force causing it. Anything which facilitates gaseous diffusion increases the strength of the auxiliary current.

In explanation of these facts, the author considers that the two atoms of a gas molecule are charged with opposite electricities, and are held together by molecular forces. When this union is ruptured by the main discharge, the atoms diffuse across to the auxiliary electrodes, and give up their electricities to them. The rupture of the molecule is supposed to take place at the negative pole. The diurnal

variations of terrestrial magnetism are supposed to be due to currents produced by tidal or other regular motions, such feeble currents being rendered possible by the more powerful discharges which take place in the upper regions of the atmosphere. H. K. T.

Conduction of Electricity through Gases. By F. NARR (Ann. Phys. Chem. [2], 33, 295-301).-Hittorf (Ann. Phys. Chem., 7, 595) found that a pair of gold leaves attached to a stick of shellac, enclosed in a tube of hydrogen containing phosphoric acid to ensure perfect dryness, retained their charge after the lapse of four days, from which he concluded that dry hydrogen does not conduct electricity. Nahrwold (ibid., 5, 460), by a different method of experimenting, came to the conclusion that the particles of a gas cannot receive an electrostatic charge, and that the loss of charge of a conductor exposed to the air is due entirely to the presence of floating particles of dust. The author considers that Nahrwold's experiments only show that dust is the chief factor in causing leakage in a conductor exposed to the air.

He refers to some former experiments (ibid. [2], 5, 145; 8, 266; 11, 155; 16, 558; 22, 550) made by him with a charged sphere suspended within an insulated conducting envelope containing different gases of various densities, carefully freed from dust. Whilst he confirmed Hittorf's result as to the charge being retained for a long time, he found that there is an instantaneous small loss of charge, depending on the nature of the gas and on its density. This instantaneous loss increases as the density is diminished, and a further instantaneous loss takes place when the envelope is connected to the earth, followed by a gradual and continuous loss of charge. The author attributes this sudden loss to a transference of electricity to the gaseous molecules, and the slow dispersion to an electrical connection between the sphere and the envelope. He has now repeated the experiments with a double metallic envelope containing gas. The envelopes were in the form of cylinders open at one end, and closed at the other, the closed ends being hemispherical. The open ends were closed by a sheet of glass covered with lac varnish, and the cylinders were cemented to it with their axes coinciding. The author then found a similar increased loss on connecting the outer envelope with the earth, from which he concludes that the gas between the two cylinders acted as a conductor, putting the inner one in connection with the outer, and so with the earth. The instantaneous loss of charge was found to increase when the density of either the inner or the outer portion of gas was diminished, which agreed with the former results, but the slow dispersion of the charge appeared to be sensibly independent of the density of the gas, as would be expected to be the case if the dispersion takes place by a convection of electricity by the gaseous particles, owing to the enormous number in contact with the surface of the envelope at any moment.

G. W. T. Electrical Conductivity of Solutions of Neutral Salts. By G. JÄGER (Monatsh., 8, 721–724).—The electrical conductivities of some salts of heavy metals have been measured in solutions con

taining proportions varying from to 50 of the gram-molecular weights per litre. The salts thus examined were lead nitrate and acetate; silver nitrate, sulphate, and acetate; zinc sulphate, bromide, and iodide, and copper sulphate and acetate. Dividing the observed conductivity by the proportion of the molecular weight in each case, the relative conductivity of the molecular weight of the salt for different dilutions is obtained. This plotted against the dilution values gives curves approximating to straight lines, although in no case could the conductivity be represented as of the form L = am + Bm2. All the curves, with the exception of that for zine bromide, appear to tend towards maxima in different directions; this is taken as supporting the view that each salt has its own definite molecular conductivity. H. C.

Comparative Properties of the Electrical Conductivities of Salt Solutions. By G. JÄGER (Monatsh., 8, 725-733).—In a former paper (this vol., p. 217), the author proved that if L and L are the molecular conductivities of two different salt solutions, & the diameter of the molecule of the solvent, and d, d', di, d'1, those of the ions, L 1/(d + ô)2 + 1/(d' + d)2

=

From this it follows that as d is

L 1/(d1 + ô)2 + 1/(d'ı + ê)2° increased, the value of L/L, will more nearly approximate to unity, or that as the size of the molecules of the solvent increase all molecular conductivities approach more nearly to the same value. A rise of temperature increasing the sphere of action of the molecule in accordance with the coefficient of expansion of the liquid, where this last is small and only small changes of temperature are dealt with, & may be looked on as constant, and the above ratio as independent of temperature.

To test the above, a determination was made of the conductivities of solutions of sodium and potassium chlorides containing to granequivalent per litre in water, and in water containing 20 to 60 per cent. alcohol, glycerol, and sugar, in each of which cases the conductivity of the solvent may be neglected. Dividing the molecular conductivity of potassium chloride by that of sodium chloride in each case, it was found, as was expected, that water gave the highest values for the ratio, and that in the other cases the ratio decreased and approximated more to unity as the quantity of dissolved alcohol, glycerol, or sugar increased, or, as may be assumed, the diameter of the molecule of the solvent increased. That temperature would have no effect on the value of the ratio may be taken as proved by the result of Kohlrausch's experiments, "that the resistances of the ions in water are all altered in the same proportion by change of temperature."

Also, as а consequence of Kohlrausch's theory, L/L, = (u + v)/(u1 + v1) where u, v, u1, and v, are the molecular velocities of the ions, it follows that if two salts have one ion in common, say, u = u1, then L/L, approximates to unity as u increases, or the greater the molecular conductivities of two salts containing a common ion, the less will the ratio of the two conductivities differ from unity. This is also found to hold good when tested by the results of Kohlrausch's own experiments. H. C.