ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
223 
ULTRAMICROSCOPY, COLLOIDS, Etc. 
Solubility of Small Particles and Stability of Colloids. — 
L. F. Knapp (Trans. Faraday Society, 1922, 17, Part 2). A theoretical 
paper of the greatest importance, in which the microscope plays a 
considerable part. A relation on thermodynamical grounds has already 
been obtained between solubility and size of solid particles. The 
stability of many colloids appears to be some function of the electric 
charge carried by the disperse phase. A mistake crept into the original 
mathematical analysis. The correct expression (Freundlich) is given in 
the present paper. F. I. G. R. 
Clays as Disperse Systems. — Sven Oden (Trans. Faraday Society, 
1922, 17, Part 2). According to the author, “ clays are disperse forma- 
tions of mineral fragments in which particles of smaller dimensions than 
2 fx predominate.” The part played by the ultramicroscope in treating 
clays as colloidal systems is considered, and also the extension of 
researches to the question of sedimentation in more viscous liquids. 
F. I. G. R. 
Plasticity of 
1922, 17, Part 2). 
Clays. — J. W. Mellor (Trans. Fccraday Society , 
A workable definition is given, i.e. 
Plasticity = - — 5 0 ^ ie ®| 0 i 1 . 
Internal inaction 
The author proceeds to discuss the property with reference to grain-size, 
colloidal clay, etc. An attempt to detect “ L’argile collo'ide ” micro- 
scopically is described. F. I. G. R. 
