﻿40 Dr. H. Stanley Allen on the 



If we assume that the active size is r = 10~ i cm., then 



T = 300(^)=284°, 

 V2o/ ' 



i.e., at this temperature, or with a supercooling of 16° C, 

 the solution would crystallize spontaneously. 



The theory now described therefore leads to the following 

 properties or! supersaturated solutions: — 



(1) It is possible for a solution to contain more solute than 

 corresponds with equilibrium in contact with a plane surface 

 of solid solute (i. e. large crystals of the latter). 



(2) Such a " supersaturated " solution can be in equi- 

 librium with particles of solid of a definite size. Smaller 

 particles dissolve in the solution, larger particles bring about 

 its crystallization. 



(3) According as the solid dissolves in its nearly saturated 

 solution with absorption or evolution of heat, the size of 

 " active" particles of solid, i.e. such as induce crystallization 

 in a given solution, decreases with fall of temperature, or rise 

 of temperature respectively. 



(4) The solution may, at a sufficiently low or high tempe- 

 rature, respectively, crystallize spontaneously. 



V. The Magnetic Field of an Atom in Relation to Theories. 

 • of Spectral Series. By H. Stanley Allen, M.A., D.Sc* 



1]S the course of a discussion on the structure of the atom 

 it w T as pointed out by the present writer f that it may 

 be necessary to take into account not only the electrostatic, 

 but also the magnetic forces in the neighbourhood of the 

 atom. It was suggested J that the atom might be regarded 

 as a central core, carrying an electric charge and producing 

 a magnetic field similar to that due to an elementary magnet, 

 the core being surrounded by electrons in orbital motion. 

 Such a magnetic core might arise from a spherical volume 

 distribution of electricity rotating about a diameter with a 

 specified angular velocity. 



One of the most important questions to be considered in 

 connexion with any atomic model is the possibility of ex- 

 plaining the lines in the spectra of the elements, and in 

 particular the relations between the frequencies of the lines 



* Communicated b}^ the Author, 

 t ' Nature,' vol. xcii. p. 630 (1914). 



X 'Nature,' vol. xcii. p. 713 (1914). Discussion on the Structure of 

 the Atom, Royal Society, p. 17, March 19, 1914. 



