Copy 1, Volume 1

Hand-book of chemistry / Translated by Henry Watts.

  • Gmelin, Leopold, 1788-1853
Date:
1848-1872
Catalogue details

Licence: Public Domain Mark

Credit: Hand-book of chemistry / Translated by Henry Watts. Source: Wellcome Collection.

    486/562 (page 462)
    again, secondary products are formed (Faraday); for ammonia is formed at the cathode (Daniell)—When iron wires are used, only the positive wire yields gas, viz., oxygen, but it likewise dissolves. The liquid at the negative wire likewise contains free ammonia, together with free potash. Zinc wires behave in the same manner, excepting that neither of them yields any gas, save a very small quantity, which appears on the negative wire every time the circuit is closed. (Hisinger & Berzelius.) Nitrate of Baryta dissolved in water is resolved into acid and base. (H. Davy.) Fused Bottle Glass is not decomposed; glass centaining lead, slightly. (Faraday.) If two cups be formed of any of the following Stliceous Minerals, filled with water—connected by asbestus—and subjected to the action ofa powerful battery—their soluble constituents collect in the two cups. Zeolite, which contains 0-7 per cent. of soda, gives in two minutes distinct ' indications of soda and lime in the negative cup: Zepidolite gives potash. _ Basalt gives soda and potash in the negative cup, chlorine in the positive cup. Vitrified Lava from Etna yields potash, soda, and lime in the nega- tive cup. (H. Davy.) Arseniate of Potash dissolved in water is slowly decomposed with separation of arsenic at the negative pole. (Bischof.) Solid Soap (stearate of soda) stops the electric current after a few seconds,—because stearic acid, which is a non-conductor, separates at the anode. ‘Touching the soap after this removes only the electricity of the negative pole. Hence we have an explanation of the Negative Unipo- larity* of soap observed by Erman. When the soap is wetted in the neighbourhood of the anode, the current is not impeded,—no unipolarity is observed. (Ohm, Schw. 59, 385.) The physiological effects which accompany the [passage of electricity through living animal bodies may be produced in either of the following ways. 1. The electricity may be actually transmitted through the solid parts of the body, and thus may directly affect the nerves. 2. It may decompose the salts contained in the liquids of the body, evolving oxygen and acid at the positive, hydrogen and alkali at the negative pole, as pointed out by Matteucci (Schw. 60, 305),—and bringing about a transpo- * In additon to Perfect Conductors and Non-conductors, Erman distinguished the following classes of conductors: 1. Bipolar Conductors (water). Water, when con- nected with one pole of the battery and with the ground, conducts away the electricity of that pole. When connected with both poles, it does not allow the electricities accumu- lated in the poles to unite; but the poles retain their former tension, and this tension is likewise exhibited in the water, so that the half of the liquid next to the positive pole appears positive, the other half negative. [The great resistance which pure water opposes to the transposition of atoms enables the electric fluids to accumulate in the poles till they attain a very high tension; but they are by no means completely insulated, —electricity is continually passing into the water.]|—2. Unipolar Conductors. Bodies of this class, like bipolar conductors, discharge each individual pole when they are con- nected with it and with the ground, and are likewise incapable, when placed between the poles, of bringing about the combination of the two electric fluids. But if when thus made to connect the poles, they are at the same time touched by a good conductor com- | municating with the ground, this conductor removes the electricity of one pole only, while that of the other remains undiminished. Positive Unipolar Conductors (the flame of alcohol and and other compounds containing carbon and hydrogen) are therefore such as when placed in the voltaic circuit communicate positive electricity to a good con- ductor;—Negative Unipolar Conductors (solid alkaline soap, dried white of egg,) on. the contrary, communicate negative electricity under the same circumstances. [The cause of this peculiar property in soap has been explained above; similar causes are pro- bably at work also in other substances in which the same peculiarity has been observed. |