Page:Various Forces of Matter.djvu/91

Rh new attraction we call chemical affinity, or the force of chemical action between different bodies; we are now no longer concerned with the attraction of iron for iron, water for water, wood for wood, or like bodies for each other as we were when dealing with the force of cohesion; we are dealing with another kind of attraction,—the attraction between particles of a different 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 show 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.