HKB
but there is no other change of the lime than that under the action of heat of this highly-exalted chemical condition, though almost any other substance would melt at once.
Then, as to the way in which the heat is applied to the substance. It is all very well for me to take a piece of antimony, and fuse it in the flame of a blowpipe. But if I tried this piece in the ordinary lamp flame, I should do nothing; if I tried a smaller piece, I should do little or nothing; and if I tried a still smaller piece, I should do little or nothing; yet I have a condition which will represent what Deville carries to the highest possible extent, and which we all carry to the highest extent, in the use of the blowpipe. Suppose I take this piece of antimony: I shall not be able to melt it in that flame of the candle by merely holding it there; yet, by taking pains, we can even melt a piece of platinum there. This is a preparation which I made for the purpose of proving the fusibility of platinum in a common candle. There is a piece of wire, drawn by that ingenious process of Dr. Wollaston’s, not more than the three-thousandth part of an inch in diameter. He put the wire into the middle of a cylinder of silver, and drew both together until the whole compound was exceedingly thin; and then he dissolved away the silver by nitric acid. There was left in the centre a substance which I can scarcely see with an eye-glass, but which I know is there, and which I can make visible, as you see, by putting it into the candle, where the heat makes it glow like a spark. I have again and again tried this experiment up-stairs in my own room, and have easily fused this platinum-wire by a common candle. You see we have, therefore, heat enough in the candle, as in the voltaic battery, or in the highly-exalted combustion of the blowpipe, but we do not supply a continuous source of heat. In the very act of this becoming ignited, the heat radiates so fast that you cannot accumulate enough to cause the fusion of the wire, except under the most careful arrangement. Thus I cannot melt that piece of antimony by simply putting it into the candle; but if I put it upon charcoal, and drive the fiery current against it, there will be heat enough to melt it. The beauty of the blowpipe is, that it sends hot air (making hot air by the combustion of the flame) against the thing to be heated. I have only to hold the antimony in the course of that current, and particle by particle of the current impinges upon the antimony, and so we get it melted. You now see it red-hot, and I have no doubt it will continue to burn if I withdraw it from the flame and continue to force the air on it. Now, you see it burning without any heat but that of its own combustion, which I am keeping up by sending the air against it. It would go out in a moment if I took away the current of air from it; but there it is burning, and the more air I give it, by this or any other action, the better it is. So, then, we have here not merely a mighty source of heat, but a means of driving the heat forcibly against substances.