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Account of some Experiments made in the Laboratory of the Royal Institution, relating to the Agencies of Galvanic Electricity, in producing Heat, and in effecting Changes in different Fluid Substances (1802?).1

in The Collected Works of Sir Humphry Davy, ed. John Davy (London: Smith, Elder and Co., 1829), II, 214-220.

{214} 1. It has been shown, by a very interesting experiment made in France, by Messrs. Fourcoy, Vauquelin, and Thenard, that the power of galvanic batteries, containing large plates, to ignite metallic substances, is much greater than that of batteries composed of an equal number of small plates; though their agencies upon water, and upon the human body, are nearly the same.

In examining the circumstances of the action of a galvanic apparatus or trough, constructed in the Royal Institution, and containing twenty series of plates of copper and zinc, square, and thirteen inches in diameter, I observed that the same relations between chemical agency and the production of galvanic electricity existed as in other cases. When pure water was used for filling the cells, the sparks, as well as the shocks, were extremely indistinct, and the battery was capable of igniting only about a line or iron wire of 1/170 of an inch in diameter. With solution of muriate of soda it acted better, and dilute nitric acid was still more efficacious. With this last substance, it became capable of rendering white-hot three inches of the {215} iron wire of 1/170, and of causing two inches to enter into fusion.

In comparing the effects produced by a solution of nitrous acid, of the specific gravity of 14, in about sixty parts of water, with those occasioned by a concentrated solution of carbonate of potash, the acid was found to produce by much the greater intensity of action, which can hardly be ascribed to any other cause than its chemical agency; for, with regard to conducting power, it appeared very much inferior to the other solution. There is every reason to believe, that with pure water, that is, water deprived of air and of all saline substances, no action would be produced in this battery. I was unable to ascertain the fact by direct experiment; but I found repeatedly, that a pile, composed of thirty-six series of square plates of copper and zinc, of five inches in diameter, lost its activity in nitrogen and hydrogen gases, in about two days; and it was constantly restored by common air, and rendered more intense by oxygen gas.

2. When the galvanic battery, with large plates, was in full action, it was found that a wire of 1/80 of an inch in diameter, and two feet long, when placed in the circuit, was rendered so hot, as to cause a small quantity of water, brought in contact with it, speedily to boil. It continued warm for many minutes; and by an occasional momentary interruption and completion of the circle, the heat was permanently kept up. When three or four inches of the wire of 1/170 were placed in any part of the conducting chain, they continued red-hot for more than a minute; and by a succession of interruptions and contacts, they were kept partially ignited for five or six minutes. When that part of the communicating chain containing the small wire was {216} introduced into a small quantity of ether, alcohol, or oil, the fluid soon became warm; and olive oil, the only substance that was exposed for a sufficient time, was made to boil.

3. When two small pieces of well-burned charcoal, or a piece of charcoal and a metallic wire, were made to complete the circle in water, vivid sparks were perceived, gas was given out very plentifully, and the points of the charcoal appeared red-hot in the fluid for some time after the contact was made; and as long as this appearance existed, elastic fluid was generated with the noise of ebullition. The sensible phenomena were nearly the same with the volatile and fixed oils, ether, and alcohol; and by means of charcoal, the spark could be produced in concentrated and sulphuric and nitric acids, which are amongst the best of the less perfect conductors.

The gases produced from different fluids by the galvano-electric spark were examined; and as the results were, in most cases, what might have been expected from theory, the analysis of them was not made with very minute attention.

When water was acted upon by sparks taken from two pieces of charcoal, the elastic products evolved were about 1/8 of carbonic acid, 1/8 of oxygen, and the remainder an inflammable gas, which required a little more than half its volume of oxygen for its combustion. With gold and charcoal, the gold being on the zinc side, the gas produced appeared to be chiefly a mixture of oxygen and hydrogen, for it diminished 7/10 by the electric spark.

The gas disengaged from alcohol, the spark being taken by gold connected with the zinc end and charcoal, was a mixture of nearly two parts of oxygen and {217} eleven parts of inflammable gas, which appeared to be light hydro-carbonate.

Ether, in the same method of operating, gave four parts of oxygen and twelve parts of inflammable gas.

From sulphuric acid, oxygen, and hydrogen, were produced very rapidly, (the oxygen being more than sufficient for the saturation of the hydrogen by combustion,) and the acid became blue.

The gas from nitric acid detonated with great violence by the electric spark, and the residuum was oxygen mixed with a little nitrogen.

The products from the acids, there is every reason to believe, were evolved chiefly in consequence of the decomposition of the water they contained. And, in operating upon these substances, as well as upon pure water, a portion of the elastic fluid must have been produced at the time of the silent transmission of the electricity, during the momentary interruption of contact. The apparent ignition of the charcoal in the different fluids depended probably, in some measure, upon its being surrounded at the moment of contact by globules of gas, which prevented the heat, produced at the points of it, from being rapidly carried off by the fluid.

When the spark was taken by means of iron wires, in phosphorus rendered fluid by heat under a stratum of water, permanent gas was produced from it, but in a quantity too small to be examined, after a process that continued an hour. I purpose to repeat the experiment with conductors of dry charcoal.

4. When gold wires, connected with the ends of the battery, were made to act upon fluids in the common method of communication, being placed at a distance from each other, it was found that the rapidity of the evolution of the gases was much more influenced by the {218} conducting power of the fluid than it is in common cases with small plates. In comparing the action of a battery of twenty plates, of five inches in diameter, upon sulphuric acid, nitric acid, and various saline solutions, with that of the large battery, it was observed in several experiments, that the gas was disengaged much faster and in larger quantities from the wires connected with the large plates, whilst the action of the two arrangements upon water was nearly the same. This fact, combined with other facts of the same kind, seems to show, that the quantity of electricity excited in the arrangements with large surfaces is much greater than that produced in those with small surfaces; and that it is capable of passing with facility through the more perfect conductors, whilst, from the nature of the series, its circulation is impeded, comparatively, to a great extent, by imperfect conductors; a conjecture that has been already formed by different philosophers.

5. As the great quantity of electricity made to circulate through perfect conductors, by means of the larger apparatus, increases their affinity for oxygen more perhaps than any known agent, and as charcoal by means of it can be rendered white-hot, and kept in constant combustion in oxygen gas or atmospherical air, I thought of trying the effects of the electrical ignition of this substance upon muriatic acid gas confined over mercury.

This experiment was made by means of a small glass tube,2 containing a slip of platina hermetically sealed into it, and having a piece of charcoal attached to its lower extremity: the communication was effected by means of iron wires, and the charcoal was made white-hot by successive contacts continued for nearly two {219} hours. At the end of this time, the muriatic acid gas had diminished a very little in volume; much white matter had formed upon the charcoal, which was not sensibly consumed. When the gas was examined, three-fourths of it were instantly absorbed by water, and the remainder proved to be inflammable. The process was repeated three times; and when the spark was most vivid, a white cloud was always perceived at the moment of its production. I am inclined to attribute this phænomenon, and the other phænomena, to the decomposition of the water held in solution in the gas, by the charcoal and the mercury adhering to it; and the white matter was probably muriate of mercury. The acid gases are rapidly absorbed by charcoal; and this substance, when well made, will take up more than thirty times its volume of muriatic acid gas; so that in the process of ignition a part of the water and of the acid must have been acted upon in a very condensed state.

The want of success in this experiment, the results of which are very similar to those obtained by Mr. Wm. Henry in his trials with common electricity, prevented me from carrying on the process upon fluoric acid gas, as I had at first intended. Many of the compound gases that are decomposable by heated charcoal, might probably, however, be analysed in a very simple manner, by means of the ignition of that substance by galvanic electricity; and this mode of operating may be conveniently applied, for ascertaining the relations of the affinities of charcoal for the constituent parts of compound gases at very high temperatures.


Fig. 1 represents the apparatus for taking the spark in fluids. A is a tube graduated to grain measures. C is a platina wire, hermetically sealed into the tube; and having a piece of charcoal attached to its top. B is a moveable platina wire, having charcoal at its top; the effect is produced by making the contact between the pieces of charcoal. In cases when the fluids are very imperfect conductors, the wires may be used without the charcoal.

Fig. 2 represents the apparatus for taking the spark in gases; it is used over mercury. A and B are the communicating platina wires, to which the charcoal is fastened; and C is the graduated tube in which the gas is acted upon.


1. [From Journals of the Royal Institution, vol. i.]

2. For a description of this apparatus, see p. 220.