[Illustration: FIG. 24.--Making carbon dioxide from marble and
hydrochloric acid.]
49. How to Obtain Carbon Dioxide. There are several ways in which
carbon dioxide can be produced commercially, but for laboratory use
the simplest is to mix in a test tube powdered marble, or chalk, and
hydrochloric acid, and to collect the effervescing gas as shown in
Figure 24. The substance which remains in the test tube after the gas
has passed off is a solution of a salt and water. From a mixture of
hydrochloric acid (HCl) and marble are obtained a salt, water, and
carbon dioxide, the desired gas.
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