A visual history of Galvanism

Exploring Galvani s room for experiments

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The original electrical machine used by Galvani in his electrophysiological experiments. This instrument is now kept at the Science Museum in London (phot by M. Bresadola)

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Galvani’s sketches of the experimental arrangement that he developed in his study of the electric stimulation of muscular motion. From Galvani’s manuscripts kept at the Bologna Academy of Sciences (photo by M. Bresadola)

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An illustration of the domestic laboratory that Galvani built in his house to perform the electrical experiments on animals. From Galvani’s De viribus electricitatis in motu musculari, 1791

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Alessandro Volta's experiments with the condensatore

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Luigi Galvani's experimental frog

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Apparatus made of Volta's battery and condensatore

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The original electrical machine used by Galvani in his electrophysiological experiments. This instrument is now kept at the Science Museum in London (phot by M. Bresadola)

Design Of Science — 2019-02-24T08:31:30Z

Medicine and science in the life of Luigi Galvani (1737–1798)

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A visual history of Galvanism

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Fig. 3: Alessandro Volta’s condensatore-electrometer

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“He armed [the electrometer] with a little condenser, fig. 3, in which he accumulated the electricity of several contacts, by making its upper plate communicate with the ground, and with the metallic disc whose electricity he wished to estimate, touching the under plate, which communicated with the leaves of the electrometer” (p. 430).

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Fig. 16: Experiment with Volta’s battery on the decomposition of water

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“We have already seen […] the singular power which the Voltaic apparatus possess of separating the constituent principles of water. This experiment, a thousand times repeated, has been elaborately studied in its details, and has led to conclusions very useful in respect to other chemical decompositions. We shall, for this reason, therefore, first of all describe this process. The most convenient apparatus for doing it well, seems to be that which has been contrived by Messrs [Joseph Louis] Gay-Lussac and [Louis Jacques] Thénard, fig. 16. E E is a glass funnel, the mouth of which B is closed by a stopper coated sealing-wax, across which two wires of platinum are made to pass parallel, and distant from each other nearly half an inch; this wires rise within the funnel an inch and a half, or two inches, above the bottom of it. Water is then poured into the funnel, and each wire is covered by a small glass tube sealed in the top, and also filled with water. The external extremities of the wires are then made to communicate each of them with a pole of the pile, and the apparatus is arranged. After it has acted for some time, the communication between the two poles is interrupted, and measuring of the volume of the gas disengaged under each covered glass, we then find twice as great a volume of hydrogen as of oxygen. These are, in fact, the proportions with constitute water; for, on re-establishing the combination, there remains no gaseous residuum; at least, when the water exposed to the electrical current has been previously deprived of its air, and is preserved from the contact of this fluid during the operation, which may be done, either by covering the funnel with a cover properly luted, or in placing it in a vacuum. Without this precaution the gases disengaged by the pile would mix with portions of atmospheric air, either previously contained in the water, or absorbed by it during the operation; so that the nature and the proportion of the product would be altered by these circumstances. But, besides this, in order to lose nothing of the action of the pile, the communication of the decomposing wires with the extreme elements must be perfectly established; and nothing is more convenient for this purpose, than plunging them into a little cup of glass filled with mercury; in which are plunged two thick wires of iron, cemented to the extreme plates of the electromotive apparatus.

With this arrangement Messrs Gay-Lussac and Thénard have observed, that the quantity of gas disengaged in a given time by the same pile, whether constructed with moistened cloths or with troughs, varies considerably according to the nature of the substances dissolved in the water with which the funnel is filled. Concentrated saline solutions, and compounds of water and acids, give the most abundant and most rapid disengagement. This phenomenon diminishes as the proportions of salt or of acid become smaller; and lastly, when the funnel contains only boiled and perfectly pure water, almost no more gas is disengaged. Thus pure water, which transmits powerfully the electricity which is excited by our ordinary machines, becomes almost an insulating substance in the case of the weak repulsive forces to which the electromotive apparatus gives rise” (p. 439).

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Figg. 14-15: Chemical phenomena in Volta’s battery

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“When we separate the elements of the piles which have been thus kept in action during several hours, or even days, under a cover which prevents the renewal of the atmospheric air, and having a constant communication kept up between their poles, we find that the metallic plates which compose them adhere to each other, and to the intermediate moistened cloths, with so great a force, that it is difficult to separate them. When this is done, we observe that the chemical action of the pile appears to have reacted on it, and produced remarkable alterations on its own elements. If the pile has been raised, according to the order, zinc, moisture, copper, zinc, &c., fig. 14, and placed on its zinc base, we observe invariably that particles detached from the inferior zinc plate have been carried to, and have fixed themselves on the plate of copper above it, while particles of copper have been transported to the superior zinc, and so on from the bottom to the top of the column. If the situation of the pile is the reverse, namely, copper, moisture, zinc, copper, &c., fig. 15, the copper descends upon the zinc, which is below it, and the zinc on the copper, from the bottom to the top of the column. The direction of the transport along the pile is reversed, but it remains the same relatively to the order of the elements of which the apparatus is composed” (p. 436).

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Fig. 13: Experiment with Volta’s battery on the absorption of oxygen

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“Among the phenomena which it produces [i.e. the electromotive apparatus], the first to be examined, because it is the most general, is a rapid absorption of the oxygen of the air around the apparatus. This may be rendered apparent in a very simple manner, by placing a vertical pile upon a support surrounded with water, and covering it with a cylindrical jar of glass, which also dips into the water at its base, fig. 13. In a few instants, the water will be seen to rise in the interior of the jar, especially if we form the communication between the two poles of the pile by metal wires, so as to direct through them the circulation of the electricity: when no communication is formed, the absorption still goes on, but with much greater slowness. In every case, in more or less time, according to the volume of the pile, and the quantity of air which surrounds it, the absorption ceases, and the air remaining under the jar presents no more traces of oxygen. This phenomenon was discovered by MM. [Jean-Baptiste] Biot and Frédéric Cuvier, when the electromotive apparatus became first known in France” (p. 436).

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Fig. 12: A modification of Volta’s battery

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“… an electrical pile formed by a mass of several plates of glass, coated with metal, and of which the opposite faces, parallel to each other, communicate by metallic conductors, fig. 12. An apparatus, indeed, constructed in this manner, being charged with ordinary electricity, presents, both in theory and in fact, an exact representation of the electrical phenomena which the electromotive apparatus produces, whether one of its poles communicates with the ground, or is in a state of insulation; and if it does not exert the same power of decomposition on chemical combinations, it is very probable that this arises from the impossibility of recharging its electrical poles instantaneously and continually, in proportion as they discharge themselves along the substances through which the electrical currents pass; a faculty which the electromotive apparatus possesses of itself, when the humid conductors, which separate its metallic elements, present a sufficiently open passage for the transmission of the electricity” (p. 435).

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