﻿Notices respecting New Books. 415 



Summary* 



(a) A separation of the particles present in a suspension 



of gum mastic has been effected by OdeVs method 

 of fractional coagulation. 



(b) The density of the particles, and the mass of mastic 



and the number of particles in unit volume have 

 been measured, and from them the interfacial 

 surface in unit volume calculated. 



(<•) The variation of the minimal concentrations of 

 A1 2 (S0 4 ) 3 , BaCl 2 , and NaCl to coagulate solutions 

 containing particles of different mean size with 

 change in concentration of the solutions has been 

 investigated. 



(d) It has been shown that uniformity in comparison of 

 the results can be obtained upon the basis of the 

 interfacial surface in unit volume. It has also been 

 shown that, upon this basis of comparison, small 

 particles require a higher minimal concentration of 

 electrolyte than large particles. 



In conclusion I should like to thank Dr. A. S. Russell for 

 his valuable advice and assistance, and Mr. H. M. Carleton 

 for kindly putting at my disposal the microscopical apparatus 

 required. 



Christ Church Laboratory, Oxford, 

 May 1 5th, 1922. 



XLI. Notices respecting New Books. 



Basic Slags and Rock Phosphates. By Gr. Scott Robertson. 

 Pp. xiv + 112, 8 plates. 1922. Cambridge Agric. Monographs. 

 Cambridge University Press. 14s. net. 



r pHE value of scientific investigation of the results accruing from 

 -*- the use of phosphatic dressings on crop-production is obvious to 

 all, but it gains in emphasis when, as Sir E. J. Russell points out 

 in a preface to the above book, agriculturists have to realize that 

 the composition of basic slag has undergone much change in 

 consequence of the enforced modifications in the processes of steel 

 manufacture. We would go farther than Sir E. J. Russell and 



