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.

    35/410 (page 19)
    ing cause the water to evaporate. If there is anything solid in solution there will be a residue on the platinum foil ov watch glass. If not, there will be no residue. Now treat a small piece of the substance with dilute hydrochloric acid and notice what takes place. Bubbles of gas are given off. After the action has continued for about a minute, insert a lighted match in the upper part of the tube. It is extinguished and the gas does not burn. The gas formed in this case is therefore plainly not identical with either one of those obtained from water by the action of the elec- tric current (see Experiment 3). It is what is commonly called carbonic acid gas. As the action continues the piece of calc-spar or marble grows smaller and smaller and finally disappears, when we have a clear solution. The substance has dissolved in the hydrochloric acid. In order to deter- mine whether anything else has taken place besides the dis- solving, we shall have to get rid of the excess of hydrochlo- ric acid. This we can easily do by boiling it, when it passes off in the form of vapor, and then whatever is in solution will remain behind. For this purpose put the solution in a small, clean porcelain evaporating-dish, and put this on a vessel containing boiling water, or a water-bath. The op- eration should be carried on in a place in which the draught is good, so that the vapors will not collect in the working- room. They are not poisonous, but they are annoying. The arrangement for evaporating is represented in Fig. 6. After the liquid has evaporated and the substance in the evaporating-dish is dry, examine it and carefully compare its properties with those of the substance which was put into the test-tube. Its structure will be found not to present the regularities noticed in the original substance. It is much softer. It dissolves in water. It melts when heated