The following paper was lately read before the French Academy of Science : It is known that when two sheets of platinum have been previously placed in contact, one with hydrogen gas and the other with oxygen, and are immersed in water mixed with sulphuric acid, they constitute, momentarily, a voltaic pairthe sheet covered with hydrogen serving as the zinc side of an ordinary pair. By arranging on the conducting liquid two tubes, half filled, one with hydrogen the other with oxygen, and immersing the sheets of platinum partly in the liquid and partly in one of the gases, the pair gives out electricity until there is no more gas in the tubes. By uniting several pairs, there is formed what has been called a gas battery ; it is worthy of notice that in this battery, when the circuit is closed, the gases contained in the tubes of each pair diminish in volume, the hydrogen twice as rapidly as the oxygen, so that the re-composition of water is operated in each element Many eminent philosophersFaraday among othersbave directed their attention to this subject, and their experiments prove that the probable cause of the disengagement of electricity is the combination of the oxygen dissolved in the liquid with the hydrogen adhering to the platinum by the intervention of this metal. The oxygen adhering to the second sheet is therefore only opposed to the polarization that would be produced by carrying over this sheet, the hydrogen that proceeds from the decomposition of the conducting liquid. Therefore the platinum, like other solid bodies employed under some circumstances, instead of this metal, is only the medium that determines the combination of the gases, and permits the circulation ot electricity. It appears from this that the nature of the conducting liquids, must have an influence on the development of electricity, and the new rsulta that are found mentioned in that part ot the treatise of M. Edmond Becquerel, which speaks of the action of hydrogen on the chloride of- gold as well as in that entitled " electric eurrent developed," confirm the truth of this assertion. The following experiment is corroborative of the.first :If a tube of very small diameter, filled with hydrogen gas, be placed in a vessel containing a concentrated solution of chloride of gold, at the end of a few days the temperature not having sensibly varied the level of the chloride of gold, inside, the tube will be very little different from what it was at first. Then introduce a piece of platinum wire, one part in the gas and the other part with its extremity, immersed in the ehloride of gold ; the gas is seen slowly to diminish in volume, and even at the end of a certain time to disappear completely, when the platinum wire rises to the top, but at the same time as the hydrogen gas disappeared, gold is precipitated in the metallic state on that part ot the platinum wire immersed in the chloride. It is to be observed that the liquid does not contain, in solution, any platinum, therefore it is not acted upon by the neutral chloride of gold, at least as tar as analysis proves ; moreover, the exterior air is not an agent in the manifestation of the phenomenon, since it is produced likewise in close vessels. To be able to judge ot the different results obtained. M. Becquerel gives the following conclusions : 1st. Platinum wire that does not reduce a neutral solution of chloride of gold, may acquire this property when the solution is placed in contact with hydrogen gas, and the wire immersed partly in the gas and partly in the solution ; gold is precipitated in the metallic state on that part of the wire immersed in the liquid, and the gas is absorbed while the deposit is going on. 2nd. This action is manifested equally in close vessels not exposed to atmospheric influence. As the liquid, after the re-action, does not contain any platinum in the solution, it results that the metal undergoes no alterationthat it only serves as a conductor, and it acts only by its pressure. These experiments appear to prove that in this circumstance there is produced, between a liquid and a gas (the chloride of gold and hydrogen), when platinum is present, an action of the same kind as between oxygen and hydrogen, under the influence of the same metal. 3rd. A piece of wire, with a sheet of gold under the same conditions, does not furnish any noticeable effect. 4. A voltaic pair may be formed with a single liquid, two sheets of platinum and one gas (hydrogen), but this latter to be in contact with one of the sheets and the liquid ; by uniting several pairs there is then a gas battery composed of a single gas, one metal and one liquid. Hitherto it had been laid down as a law, that with the platinum and acid solution,two gases (oxygen and hydrogen) were necessary to obtain this result; only the elements of the battery formed with the chlorirle of gold, have a feebler intensity of action than the usual gas pairs. 5th. The solution of chloride of gold, chemically pure, may therefore be considered definitively as superseding the acid solution and oxygen in the gis battery. The remarkable effects that are manifested in this circumstance should not be confounded with those that would be produced by certain gaseous solutions or liquids, such as nitric acid absorbing hydrogen at the ordinary temperature, without the appliance of platinum.
This article was originally published with the title "Observations Relative to the Electro-Chemical Properties of Hydrogen"