Electricity Treated Experimentally; For the Use of Schools and Students (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1891 edition. Excerpt: ...will be confirmed through all our experiments, since we shall find that the liquid obeys exactly the same laws as the solid conductor while the current is passing. In every battery, then, we shall assume that the current in the liquid is from the zincode to the platinode, and in the external conductor from the platinode to the zincode. 125. Electrolysis of Potassium Iodide.--Let us now place the terminals of a zinc-copper or other cell on opposite sides of a piece of blotting or other kind of bibulous paper moistened with potassium iodide. Near the end of the wire in connection with the copper will appear a brown discoloration owing to the liberation of iodine. If the bibulous paper be first soaked in a solution of starch, the discoloration becomes blue owing to the action of the liberated iodine on the starch. To actions of which this is the type Faraday gave the general name of Electrolysis, and to him we owe the very full investigation of the general laws on which the action depends. 126. Electrolysis of Water.--Although the decomposition of potassium iodide can be shown by a very weak cell, many substances can only be decomposed by very powerful batteries. The decomposition of water is easily shown with a battery of four or five Grove cells. For exhibiting the decomposition, some kind of voltameter must be used. This, in the form shown (Fig. 123), consists of two glass tubes, calibrated to measure the volumes of the gases given off. In each tube is a platinum plate half an inch wide and four or five inches long, with a platinum wire welded to it, which is fused through the glass tube, and enables communication to be made with the battery. These tubes communicate either by being parts of the same U-shaped tube (Fig. 123), or by being inverted...