Page:The chemical history of a candle.djvu/222

put all the company around me in a bath of mercury vapour. And so, if we take this piece of lead and treat it in the same way, it will also give off vapour. Observe the fumes that rise from it; and even if it was so far enclosed from the air that you could not form any litharge, you would still have those abundant fumes flying off. I may also take a piece of gold, and shew you the same thing. I have here a piece of gold which I put upon a clean surface of Paris limestone. Applying the heat of the blowpipe to it, you see how the heat drives off the vapour; and if you notice at the end of the Lecture, you will observe on the stone a purple patch of condensed gold. Thus you see a proof of the volatilisation of gold. It is the same with silver. You will not be startled if I sometimes use one agent and sometimes another to illustrate a particular point. The volatility of gold and silver is the same thing, whether it be effected by the voltaic battery or by the blowpipe. [A lump of silver was placed in a charcoal crucible between the poles of a voltaic battery.] Now, look at the fumes of silver, and observe the peculiar and beautiful green colour which they produce.