The Effect of Low Temperature on Hens' Eggs

Colloids when frozen do not as a rule recover their original state on thawing. Stiles quotes many such cases, a well-known example being a gel of silicic acid which is separated by freezing and thawing into a mixture of water and solid flakes of acid. Similarly, when a solution of chlorophyll in water is frozen slowly, the chlorophyll on thawing is found to be aggregated into large flocks which slowly settle to the bottom. Recovery of state, however, takes place in certain systems, not necessarily the simplest, if the rate of freezing be high enough. The solution of chlorophyll furnishes an example. If it be frozen in liquid air it completely recovers its original state on thawing. Obviously the end temperature does not matter because it may be said with certainty that the frozen mass could be kept at the temperature of liquid air indefinitely without losing the capacity of reforming a solution on thawing. There must therefore exist a certain limited range of temperature within which alone the process of desolution can occur. Let us call this the critical range. The peculiar feature of any temperature within the critical range θ1 - θ2 is that, if the system be kept at that temperature for a critical length T of time, changes take place which are not reversed on thawing.