CAROLINE.
It feels even colder than ice, and yet the snow is melted. This is very extraordinary.
MRS. B.
The cause of the intense cold of the mixture is to be attributed to the change from a solid to a fluid state. The union of the snow and salt produces a new arrangement of their particles, in consequence of which they become liquid; and the quantity of caloric, required to effect this change, is seized upon by the mixture wherever it can be obtained. This eagerness of the mixture for caloric, during its liquefaction, is such, that it converts part of its own free caloric into latent heat, and it is thus that its temperature is lowered.
EMILY.
Whatever you put in this mixture, therefore, would freeze?
MRS. B.
Yes; at least any fluid that is susceptible of freezing at that temperature. I have prepared this mixture of salt and snow for the purpose of freezing the water from which you are desirous of seeing the latent heat escape. I have put a thermometer in the glass of water that is to be frozen, in order that you may see how it cools.
CAROLINE.
The thermometer descends, but the heat which the water is now losing, is its free, not its latent heat.