Scientific American Supplement No. 819, September 12, 1891

by Various

THE PRODUCTION OF HYDROGEN AND OXYGEN THROUGH THE ELECTROLYSIS OF WATER.

All attempts to prepare gaseous fluids industrially were premature as long as there were no means of carrying them under a sufficiently diminished volume. For a few years past, the trade has been delivering steel cylinders that permit of storing, without the least danger, a gas under a pressure of from 120 to 200 atmospheres. The problem of delivery without pipe laying having been sufficiently solved, that of the industrial production of gases could be confronted in its turn. Liquefied sulphurous acid, chloride of methyl, and carbonic acid have been successively delivered, to commerce. The carbonic acid is now being used right along in laboratories for the production of an intense coldness, through its expansion. Oxygen and nitrogen, prepared by chemical processes, soon followed, and now the industrial electrolysis of water is about to permit of the delivery, in the same manner, of very pure oxygen and hydrogen at a price within one's reach.

Before describing the processes employed in this preparation, we must answer a question that many of our readers might be led to ask us, and that is, what can these gases be used for? We shall try to explain. A prime and important application of pure hydrogen is that of inflating balloons. Illuminating gas, which is usually employed for want of something better, is sensibly denser than hydrogen and possesses less ascensional force, whence the necessity of lightening the balloon or of increasing its volume. Such inconveniences become serious with dirigible balloons, whose surface, on the contrary, it is necessary to diminish as much as possible. When the increasing interest taken in aerostation at Paris was observed, an assured annual output of some hundreds of cubic meters of eras for the sole use of balloons was foreseen, the adoption of pure hydrogen being only a question of the net cost.

Pure or slightly carbureted hydrogen is capable of being substituted to advantage for coal gas for heating or lighting. Such an application is doubtless somewhat premature, but we shall see that it has already got out of the domain of Utopia. Finally the oxyhydrogen blowpipe, which is indispensable for the treatment of very refractory metals, consumes large quantities of hydrogen and oxygen.

For a few years past, oxygen has been employed in therapeutics; it is found in commerce either in a gaseous state or in solution in water (in siphons); it notably relieves persons afflicted with asthma or depression; and the use of it is recommended in the treatment of albumenuria. Does it cure, or at least does it contribute to cure, anæmia, that terrible affection of large cities, and the prime source of so many other troubles? Here the opinions of physicians and physiologists are divided, and we limit ourselves to a mention of the question without discussing it.

Only fifteen years ago it would have been folly to desire to obtain remunerative results through the electrolysis of water. Such research was subordinated to the industrial production of electric energy.

We shall not endeavor to establish the priority of the experiments and discoveries. The question was in the air, and was taken up almost simultaneously by three able experimenters—a Russian physicist, Prof. Latchinof, of St. Petersburg, Dr. D'Arsonval, the learned professor of the College of France, and Commandant Renard, director of the military establishment of aerostation at Chalais. Mr. D'Arsonval collected oxygen for experiments in physiology, while Commandant Renard naturally directed his attention to the production of pure hydrogen. The solutions of the question are, in fact, alike in principle, and yet they have been developed in a very different manner, and we believe that Commandant Renard's process is the completest from an industrial standpoint. We shall give an account of it from a communication made by this eminent military engineer, some time ago, to the French Society of Physics.

Transformations of the Voltameter.—In a laboratory, it is of no consequence whether a liter of hydrogen costs a centime or a franc. So long as it is a question of a few liters, one may, at his ease, waste his energy and employ costly substances.

The internal resistance of a voltameter and the cost of platinum electrodes of a few grammes should not arrest the physicist in an experiment; but, in a production on a large scale, it is necessary to decrease the resistance of the liquid column to as great a degree as possible—that is to say, to increase its section and diminish its thickness. The first condition leads to a suppression of the platinum, and the second necessitates the use of new principles in the construction of the voltameter. A laboratory voltameter consists either of a U-shaped tube or of a trough in which the electrodes are covered by bell glasses (Fig. 1, A and B). In either case, the electric current must follow a tortuous and narrow path, in order to pass from one electrode to the other, while, if the electrodes be left entirely free in the bath, the gases, rising in a spreading form, will mix at a certain height. It is necessary to separate them by a partition (Fig. 1, C). If this is isolating and impermeable, there will be no interest in raising the electrodes sensibly above its lower edge. Now, the nearer together the electrodes are, the more it is necessary to lower the partition. The extension of the electrodes and the bringing of them together is the knotty part of the question. This will be shown by a very simple calculation.