Under-cooled liquids

H. W. B. Roozeboom suggested that the relations between white and red phosphorus may be like those of cyanogen, and that the vap. press, curve of liquid yellow phosphorus may terminate below the m.p. of the violet form he also said that it may be that liquid yellow phosphorus is super-cooled violet phosphorus. A. Smits and co-workers showed that liquid yellow phosphorus is to be taken as super-cooled liquid violet phosphorus. It is usual to consider under-cooled liquids as being still in the liquid state, and since yellow phosphorus crystallizes in the... 

A. Stock found that the m.p. of phosphorus depends on the rate of heating and in contradistinction to A. Smits and H. L. de Leeuw, A. Stock and E. Stamm did not find the m.p. of yellow phosphorus to be altered by heating it to 100° followed by rapid cooling. Molten phosphorus is easily obtained as an under-cooled liquid, even at temp. 40° below its m.p. A. Bellani, and H. Rose noted that contact with solid phosphorus causes an immediate solidification of the under-cooled liquid. The phenomenon is particularly marked with phosphorus which has been boiled under an aq. or alcoholic soln. of potassium hydroxide. Observations on this subject were made by T. de Grotthus, J. B. Kallhofert, A. Schrotter, F. P. Venable and A. W. Belden, P. Heinrich, J. W. Retgers, and D. Gernez. The last-named also measured the velocity of crystallization of the under-cooled liquid—vide supra. 

They represented their results by logi0 p=19-2189 —3585-96T-1—3-59 logjq T mm. and on the assumption, rendered probable by the work of L. Troost and P. Hautefeuille, and A. Smits and co-workers, that under-cooled liquid violet phosphorus... 

Tr = 0. 88 Tc i for under cooled liquid + grams/100 crams solvent... 

Cavitation in an under-cooled liquid can cause nucleation, and this probably accounts for a number of the above reported effects. Hunt and Jackson (1966) demonstrated, by a novel experimental technique, that nueleation occurs when a cavity collapses rather than when it expands. Very high pressures ( 10 bar) can be generated by the collapse of a cavity the change in pressure lowers the crystallization temperature of the liquid and nucleation results. It is even suggested that nucleation caused by seratehing the side of the containing vessel could be the result of cavitation effects. 

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