The new chemistry / by Josiah P. Cooke, Jr.

  • Josiah P. Cooke
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: The new chemistry / by Josiah P. Cooke, Jr. Source: Wellcome Collection.

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    (with sulphuric acid), in order to make it a conductor of electricity. Connected with the cell is what must be known to all of my aiidience as a voltaic battery. The conducting wires from the end plates of this com- bination terminate in the two strips of platinum, which you see projected on the screen. As soon as the con- nections are made, or, to use the technical phrase, as soon as the circuit is closed, an electric cui*rent flows through the water in the cell, passing from one of these poles to the other. The eflfect of this cun-ent is visible. Bubbles of gas collect upon the platinum strips, and, as soon as they attain sufficient size, rise to the surface of the water, and this evolution of gas will go on so long as the electric current continues to flow. The gases evolved at the two poles are wholly different substances, and, in order to exhibit to you their charac- teristic qualities, I have prepared a second experiment: Standing on the table is a decomposing cell similar to the last, but very much larger, and so constructed that the two gases are collected as they rise from the poles, and conducted apart into these two glass bells. A very powerful electric current has been passing through the water in the cell since the beginning of the lecture, and already the bells are filled with the two aeriform products. Both are invisible, but notice that the gas we have collected in the right-hand bell takes fire and burns with a pale and barely luminous flame. Here we have a very large bell full of the same gas, and on lighting this I think the flame will be visi- ble to all. Every one must have recognized this ma- terial. It is a well-known substance, which we call hydro- gen. It is one of the very few substances which we only know in the aeriform condition. It is, moreover,
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