Page:On the various forces of nature and their relations to each other.djvu/98

94 nature one to the other. Chemical affinity depends entirely upon the energy with which particles of different kinds attract each other. Oxygen and hydrogen are particles of different kinds, and it is their attraction to each other which makes them chemically combine and produce water.

I must now shew you a little more at large what chemical affinity is. I can prepare these gases from other substances, as well as from water; and we will now prepare some oxygen. Here is another substance which contains oxygen—chlorate of potash. I will put some of it into this glass retort, and Mr. Anderson will apply heat to it. We have here different jars filled with water; and when, by the application of heat, the chlorate of potash is decomposed, we will displace the water, and fill the jars with gas.

Now, when water is opened out in this way by means of the battery—which adds nothing to it materially, which takes nothing from it materially (I mean no matter; I am not speaking of force), which adds no matter to the water—it is changed in this way: the gas