An introduction to the study of chemistry / by Ira Remsen.

  • Ira Remsen
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: An introduction to the study of chemistry / by Ira Remsen. Source: Wellcome Collection.

    23/410 (page 7)
    turn the tube constantly around its long axis so that the heat may act uniformly upon it. Put into it enough red oxide of mercury (mercuric oxide) to form a layer about 12 millimetres inch) thick. Heat the tube as in the last experiment. You will notice that the color of the substance is changed, and after a time minute globules ol mercury will he deposited in the upper part of the tube, and, on cooling, these will collect together and fall down, so that the presence of the mercury is readily seen. Il during the heating a splinter of wood which has a spark on the end be thrust into the tube, the spark will burst into flame and the wood will burn much more actively than it would in the air. By taking it out of the tube and putting it back again a few times, the difference between the burning in the tube and out of it will be shown very clearly. We see thus that by heat the red oxide of mercury is changed. We get in place of it mercury, which we see in the tube, and an invisible substance which is evidently in the tube, as is shown by the active burning of the wood. The red oxide of mercury has disappeared, and new sub- stances have appeared in its place. A change in composi- tion has been effected. Or a chemical change has been caused by heat. In a galvanic battery there are always substances which are undergoing changes in composition, and the electric current is due to these changes. It is therefore true that electric currents are produced by chemical changes. A simple form of a battery is represented in Fig. 2. The plates marked h are of copper, those marked of zinc. The plates are connected together by wires, as shown. In each vessel there is poured a mixture of sulphuric acid and water. This mixture acts upon the zinc, producing a