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.

    22/410 (page 6)
    undergoing a change in composition, and, as a result of this change, heat is produced. The heat is, therefore, produced by a chemical change in the coal, and we may say that the motion of the steam-engine is the result of the chemical change taking place in the coal or wood which, in burning, produces the heat. Just as in all ordinary fires we have heat produced as a result of chemical changes in the fuel, so we may have chemical changes produced by heat or by electricity. Experiment 1.—In a clean, dry test-tube put enough white sugar to make a layer to an inch thick. Hold the tube in the flame of a spirit-lamp or a laboratory burner, as shown in Fig. 1. Liquids are given off and these con- dense in the upper part of the tube. A black mass, charcoal, remains behind. It is evident that a change in composi- tion has been effected. There is no sugar left. In place of the familiar,, white, sweet substance which dissolves in water, we have left a black, tasteless substance which does not dissolve in water. This change has been produced by heat. Fig. 1. Experiment 2.—From a piece of glass tubing of about 6 to 7 millimetres inch) internal diameter cut off a piece about 10 centimetres (4 inches) long by making a mark across it with a triangular file, and then seizing it with both hands, one on each side of the mark, pulling and at the same time pressing slightly as if to break it. Clean and dry it, and hold one end in the flame of a laboratory burner until it melts together. During the melting