Physics. — “The Process of Solidification as a Problem of 
Conduction of Heat’. By Dr. H. C. Burger. (Communicated 
by Prof. W. H. Jurros). 
(Communicated at the meeting of June 26, 1920). 
- § 4. Introduction. The equilibrium between two phases has been 
fully investigated experimentally and theoretically. Little, however, 
is known about the cases in which there is no equilibrium, but 
one phase is converted into another. In the first case the thermo- 
dynamic laws may serve as basis of all considerations; in the second 
case, however, such leading principles are entirely wanting. The 
researches on the dynamics of the conversion of phases are quite 
detached, and are often restricted to the collecting of empirical data 
the meaning of which is not quite clear. 
It would be ‘very desirable to develop a general theory of 
dynamics, which will have to inelude ‘thermodynamics’ as the 
special case of its statics. Whether this is possible from a purely 
phenomenological point of view, further experiment will have to 
teach. 
In what follows I have worked out a general method for the 
treatment of the special case of the solidification of a chemically 
simple substance. 
On transition of a supercooled melt into the solid condition the 
following processes should be sharply distinguished : 
1. The formation of particles of the solid phase in the supercooled 
liquid *). 
2. The further growth of each of these particles, and also the 
growth of a particle of the solid substance put into the Jiquid 
purposely *). 
Only the second point will be treated in this communication. In 
this the particularities which are in connection with the anisotropy 
of the solid substance will not be taken into account. In this way 
the problem is simplified, but at the same time the idea of accounting 
for the formation of the crystalline form is abandoned. 
1) G. Tammany, Zeitschr. f. phys. Chem. 25, p. 442, 1898. 
*) D. GERNEz, Compt. rend. 95, p. 1278, 1882. 
B. Moors, Zeitschr. f. Phys. Chem. 12, p. 545, 1893. 
