No; for if one of the constituents of water is converted into a gas, the other becomes solid in combining with the metal. EMILY. In this case, then, neither heat nor cold should be produced? MRS. B. True: but observe that the sensible heat which is disengaged in this operation, is not owing to the decomposition of the water, but to an extrication of heat produced by the mixture of water and sulphuric acid. I will mix some water and sulphuric acid together in this glass, that you may feel the surprising quantity of heat that is disengaged by their union--now take hold of the glass---- CAROLINE. Indeed I cannot; it feels as hot as boiling water. I should have imagined there would have been heat enough disengaged to have rendered the liquid solid. MRS. B. As, however, it does not produce that effect, we cannot refer this heat to the modification called latent heat. We may, however, I think, consider it as heat of capacity, as the liquid is condensed by its loss; and if you were to repeat the experiment, in a graduated tube, you would find that the two liquids, when mixed, occupy considerably less space than they did separately. --But we will reserve this to another opportunity, and attend at present to the hydrogen gas which we have been producing. If I now set the hydrogen gas, which is contained in this receiver, at liberty all at once, and kindle it as soon as it comes in contact with the atmosphere, by presenting it to a candle, it will so suddenly and rapidly decompose the oxygen gas, by combining with its basis, that an explosion, or a _detonation_ (as chemists commonly call it), will be produced. For this purpose, I need only take up the receiver, and quickly present its open mouth to the candle---- so . . . . CAROLINE. It produced only a sort of hissing noise, with a vivid flash of light. I had expected a much greater report. MRS. B. And so it would have been, had the gases been closely confined at the moment they were made to explode. If, for instance, we were to put in this bottle a mixture of hydrogen gas and atmospheric air; and if, after corking the bottle, we should kindle the mixture by a very small orifice, from the sudden dilatation of the gases at the moment of their combination, the bottle must either fly to pieces, or the cork be blown out with considerable violence. CAROLINE. But in the experiment which we have just seen, if you did not kindle the hydrogen gas, would it not equally combine with the oxygen? MRS. B. Certainly not; for, as I have just explained to you, it is necessary that the oxygen and hydrogen gases be burnt together, in order to combine chemically and produce water. CAROLINE. That is true; but I thought this was a different combination, for I see no water produced. MRS. B.