We shall have to pay a little more attention to the forces existing in water before we can have a clear idea on the subject. Besides the attraction which there is between its particles to make it hold together as a liquid or a solid, there is also another force, different from the former—one which, yesterday, by means of the voltaic battery, we overcame, drawing from the water two different substances—which, when heated by means of the electric spark, attracted each other, and rushed into combination to reproduce water. Now, I propose to-day to continue this subject, and trace the various phenomena of chemical affinity; and for this purpose, as we yesterday considered the character of oxygen, of which I have here two jars (oxygen being those particles derived from the water which enable other bodies to burn), we will now consider the other constituent of water; and, without embarrassing you too much with the way in which these things are made, I will proceed now to shew you our common way of making hydrogen. (I called it hydrogen yesterday—it is so called because it helps to generate water.)[A] I put into this retort some zinc, water, and oil of vitriol, and immediately an action takes place, which produces an abundant evolution of gas, now coming over into this jar, and bubbling up in appearance exactly like the oxygen we obtained yesterday.
[A] ὕδωρ, “water,” and γενναω, “I generate.”.
Fig. 27.
The processes, you see, are very different, though the result is the same, in so far as it gives us certain gaseous particles. Here, then, is the hydrogen. I shewed you yesterday certain qualities of this gas; now let me exhibit you some other properties. Unlike oxygen, which is a supporter of combustion, and will not burn, hydrogen itself is combustible. There is a jar full of it; and if I carry it along in this manner, and put a light to it, I think you will see it take fire, not with a bright light—you will at all events hear it, if you do not see it. Now, that is a body entirely different from oxygen: it is extremely light; for although yesterday you saw twice as much of this hydrogen produced on the one side as on the other, by the voltaic battery, it was only one-eighth the weight of the oxygen. I carry this jar upside-down. Why? Because I know that it is a very light body, and that it will continue in this jar upside-down quite as effectually as the water will in that jar which is not upside-down; and just as I can pour water from one vessel into another in the right position to receive it, so can I pour this gas from one jar into another when they are upside-down. See what I am about to do. There is no hydrogen in this jar at present, but I will gently turn this jar of hydrogen up under this other jar (fig. 28), and then we will examine the two. We shall see, on applying a light, that the hydrogen has left the jar in which it was at first, and has poured upwards into the other, and there we shall find it.
Fig. 28.
You now understand that we can have particles of very different kinds, and that they can have different bulks and weights; and there are two or three very interesting experiments which serve to illustrate this. For instance, if I blow soap bubbles with the breath from my mouth, you will see them fall, because I fill them with common air, and the water which forms the bubble carries it down. But now, if I inhale hydrogen gas into my lungs (it does no harm to the lungs, although it does no good to them), see what happens. [The Lecturer inhaled some hydrogen, and after one or two ineffectual attempts, succeeded in blowing a splendid bubble, which rose majestically and slowly to the ceiling of the theatre, where it burst.] That shews you very well how light a substance this is; for, notwithstanding all the heavy bad air from my lungs, and the weight of the bubble, you saw how it was carried up. I want you now to consider this phenomenon of weight as indicating how exceedingly different particles are one from the other; and I will take as illustrations these very common things—air, water, the heaviest body, platinum, and this gas: and observe how they differ in this respect; for if I take a piece of platinum of that size (fig. 29), it is equal to the weight of portions of water, air, and hydrogen of the bulks I have represented in these spheres. And this illustration gives you a very good idea of the extraordinary difference with regard to the gravity of the articles having this enormous difference in bulk. [The following tabular statement having reference to this illustration appeared on the diagram board.]
Fig. 29