Text: We may in this case also observe polarization of the electrodes as a symptom of previous electrolysis. Connect the two pieces of platinum in oil of turpentine with a battery of eight Daniells, let it stand twenty-four hours, then take away the battery, and connect the electrodes with a quadrant electrometer. It will indicate that the two surfaces of platinum, which were homogenous before, produce an electromotive force which deflects the needle of the electrometer. The electromotive force of this polarization has been determined in some instances by Mr. Picker in the laboratory of the University of Berlin; he has found that the polarization of alcohol decreases with the proportion of water which it contain, and that that of the purest alcohol, ether, and oil of turpentine is about 0.3, that of benzene 0.8 of a Daniell element. Another sign of electrolytic conduction is that liquids placed between two different metals produce an electromotive force. This is never done by metals of equal temperature or by other conductors which, like metals, let electricity pass without being decomposed. The production of an electromotive force is observed even with a great many rigid bodies, although very few of them allow us to observe electrolytic conduction with the galvanometer, and even these only at temperatures near their melting points. I remind you of the galvanic pile of Zamboni, in which pieces of dry paper are intercalated between thin leaves of metal. If the connection lasts long enough, even glass, resin, shellac, paraffin, sulfur -- the best insulators we know -- do the same. It is nearly impossible to prevent the quadrants of a delicate electrometer from being charged by the insulating bodies by which they are supported. In all the cases which I have quoted, one might suspect that traces of humidity absorbed by the substance or adhering to their surface were the electrolytes. I show you, therefore, this little Daniell's cell (Fig. 2) constructed by my former assistant, Dr. Giese, in which a solution of sulfate of copper, with a platinum wire, a, as an electrode, is enclosed in a bulb of glass hermetically sealed. This is surrounded by a second cavity, sealed in the zinc sulfate and some amalgam of zinc, to which a second platinum wire, b, enters through the glass. The tubes c and d have served to introduce the liquids and have been sealed afterward. It is, therefore, like a Daniell cell in which the porous septum has been replaced by a thin stratum of glass. Externally all is symmetrical at the two poles; there is nothing in contact with the air but a closed surface of glass, through which two wires of platinum penetrate. The whole charges the electrometer exactly like a Daniell cell of very great resistance, and this it would not do if the septum of glass did not behave like an electrolyte, for a metallic conductor would completely destroy the action of the cell by its polarization. All these facts show that electrolytic is not at all limited to solutions of acids or salts. It will, however, be rather a difficult problem to find out how far the electrolytic conduction is extended, and I am not yet prepared to give a positive answer. What I intended to remind you of was only that the faculty to be decomposed by electric motion is not necessarily connected with a small resistance, but the illustration which they give us about the connection of electric and chemical force is not at all limited to the acid and saline solutions usually employed. Hitherto we have studied the motions of ponderable matter, as well as of electricity, going on in an electrolyte. Let us now study the forces which are able to produce these motions. It has always appeared somewhat startling to everybody who knows the mighty power of chemical forces and the enormous quantity of heat and mechanical work which they are able to produce, how exceedingly small is the electric attraction at the poles of a battery of two Daniell cells, which nevertheless is able to decompose water. One gram of water, produced by burning hydrogen with oxygen, develops so much heat that this heat, transformed by a steam engine into mechanical work, would raise the same weight to a height of 1,600,000 meters. And on the contrary we have to use the most delicate contrivances to show that a gold leaf or a little piece of aluminum hanging on a silk fiber can be at all moved by the electric attraction of the battery. The solution of this riddle is found if we look at the quantities of electricity with the atoms appear to be charged. The quantity of electricity which can be conveyed by a very small quantity of hydrogen, when measured by its electrostatic forces, is exceedingly great. Faraday saw this and endeavored in various ways to give at least an approximate determination. He ascertained that even the most powerful batteries of Leyden jars, discharged through a voltmeter, give scarcely any visible traces of gases. At the present we can give definite-numbers. The electrochemical equivalent of the electromagnetic unit of galvanic current has been determined by the Bunsen and more recently by other physicists. This determination was followed by the very difficult comparison of the electromagnetic and electrostatic effects of electricity, accomplished at first by Professor W. Weber and afterward, under the auspices of the British Association, by Professor Clerk Maxwell. The result is that the electricity of one milligram of water, separated and communicated to two balls one kilometer distant, would produce an attraction between them equal to the weight of 26,800 kilograms. [The amount of electricity contained in one milligram of water would be twice as much, and the attraction of both quanta four times as much, that is, equal to the weight of 102,180 kilograms. (Added in 1884 to the German translation.)] As I have already remarked, the law that the intensity of the force is inversely proportional to the square of the distance, and directionally proportional to the quantities of the attracting and attracted masses, holds good as well in the case of gravitation acting between two quantities of hydrogen and oxygen with the attraction of their electrical charges. The result will be independent of the size and the distance of these quantities. We find that the electric force is as great as the gravitation of ponderable masses, being 71,000 billion times greater than that of the oxygen and hydrogen containing these electric charges. The total force exerted by the attraction of an electrified body upon another charged with opposite electricity is always proportional to the quantity of electricity contained on the attracting as on the attracted body. Although, therefore, the attracting forces exerted by the poles of a little battery able to decompose water on such electrical charges as we can produce with our electric machines are very moderate, the forces exerted by the same little apparatus on the enormous charges of the atoms in one milligram of water may very well compete with the mightiest chemical affinity. If we now turn to investigate how the motions of the ponderable molecules are dependent upon the action of these forces, we must distinguish two different cases. At first we may ask, what forces are wanted to call forth motions of the ions with their charge through the interior of the fluid? Secondly, what are wanted to separate the ion from the fluid and its pervious combinations? Let us begin with the case in which the conducting liquid is surrounded everywhere by insulating bodies. Then no electricity can enter, and none can go out through its surface; but positive electricity can be driven to one side, negative to the other, by the attracting and repelling forces of external electrified bodies. This process, going on as well in every metallic conductor, is called electrostatic induction. Liquid conductors behave quite like metals under these conditions. Great quantities of electricities are collected, if large parts of the surfaces of the two bodies are very near each other. Such an arrangement is called an electric condenser. We can arrange electric condensers in which one of the surfaces is that of a liquid, as Messrs, Ayrton and Perry have done lately. The water-dropping collector of electricity, invented by Sir W. Thomson, is a peculiar form of such a condenser, which can be charged with perfect regularity by the slightest electromotive force perceptible only to the most sensitive electrometers. Professor Wullner has proved that even our best insulators, exposed to electric forces for a long time, are ultimately charged quite in the same way as metals would be charged in an instant. There can be no doubt that even electromotive forces less than 1/100 Daniell produce perfect electric equilibrium in the interior of an electrolytic liquid.

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