in philosophy, the same with congelation. See Congelation and Frost.

Philosophers are by no means agreed as to the cause of this phenomenon. The Cartesians account for it by the recess or going out of the ethereal matter from the pores of the water. The corpuscularians, on the other hand, attribute it to the ingress of frigorific particles, as they call them; and Hobbes affirms, that these particles icles are nothing else but common air, which entangling itself with the particles of water, prevents their motion. Others will have a kind of nitrous salt to be the cause of congelation, by insinuating itself between the particles of water, and fixing them together, like nails. And, indeed, it seems probable that cold and freezing do arise from some substance of a saline nature floating in the air; since all salts, and particularly nitrous ones, when mixed with ice and snow, greatly increase their cold, and even bulk.

Boerhave observes, that it is extremely difficult to exhibit to the eye the precise degree of cold wherein ice begins to form; since heat and cold, once given to a body, adhere long to it before they quit it. When the air, therefore, is in such a state as keeps Fahrenheit's thermometer at 32 degrees, water will not freeze; because water being 800 times denser than air, retains the warmth considerably longer than air. If any person, therefore, is curious to know in what degree of cold water begins to freeze, let him first suspend a thermometer in a free open air on all sides; and then wetting a thin linen cloth with clear water, and hanging it likewise in the open air, it will grow stiff upon the first access of the freezing cold, and thereby shew when water is beginning to turn to ice. See Thermometer.

By means of freezing, wine, vinegar, and malt-liquors may be reduced to a fourth part of their quantity, without any considerable loss of their essential parts; since only the aqueous parts freeze, leaving the vinous parts concentrated or brought into less compass, and capable of being transported with less expense, and keeping for several years.

Freezing mixtures. Mr Boyle shews in his history of cold, that not only all kinds of salts, but likewise spirits, sugar, and saccharum saturni, mixed with snow, are capable of freezing most fluids; and the same effect was also produced by the mixture of oil of vitriol, or spirit of nitre with snow.