And can you show us any experiments in which liquids, by being mixed, become solid, and disengage latent heat? MRS. B. I could show you several; but you are not yet sufficiently advanced to understand them well. I shall, however, try one, which will afford you a striking instance of the fact. The fluid which you see in this phial consists of a quantity of a certain salt called _muriat of lime_, dissolved in water. Now, if I pour into it a few drops of this other fluid, called _sulphuric acid_, the whole, or very nearly the whole, will be instantaneously converted into a solid mass. EMILY. How white it turns! I feel the latent heat escaping, for the bottle is warm, and the fluid is changed to a solid white substance like chalk! CAROLINE. This is, indeed, the most curious experiment we have seen yet. But pray what is that white vapour that ascends from the mixture? MRS. B. You are not yet enough of a chemist to understand that. --But take care, Caroline, do not approach too near it, for it has a very pungent smell. I shall show you another instance similar to that of the water, which you observed to become warmer as it froze. I have in this phial a solution of a salt called sulphat of soda or Glauber’s salt, made very strong, and corked up when it was hot, and kept without agitation till it became cold, as you may feel the phial is. Now when I take out the cork and let the air fall upon it, (for being closed when boiling, there was a vacuum in the upper part) observe that the salt will suddenly crystallize. . . . CAROLINE. Surprising! how beautifully the needles of salt have shot through the whole phial! MRS. B. Yes, it is very striking--but pray do not forget the object of the experiment. Feel how warm the phial has become by the conversion of part of the liquid into a solid. EMILY. Quite warm I declare! this is a most curious experiment of the disengagement of latent heat. MRS. B. The slakeing of lime is another remarkable instance of the extrication of latent heat. Have you never observed how quick-lime smokes when water is poured upon it, and how much heat it produces? CAROLINE. Yes; but I do not understand what change of state takes place in the lime that occasions its giving out latent heat; for the quick-lime, which is solid, is (if I recollect right) reduced to powder, by this operation, and is, therefore, rather expanded than condensed. MRS. B. It is from the water, not the lime, that the latent heat is set free. The water incorporates with, and becomes solid in the lime; in consequence of which, the heat, which kept it in a liquid state, is disengaged, and escapes in a sensible form. CAROLINE. I always thought that the heat originated in the lime. It seems very strange that water, and cold water too, should contain so much heat. EMILY. After this extrication of caloric, the water must exist in a state of ice in the lime, since it parts with the heat which kept it liquid. MRS. B.