148 Scientific Intelligence. 



polymers of a substance would render the material more active 

 and this is apparently confirmed. A high capacity silica may be 

 de-activated by a heating which does not destroy the capillaries 

 since 20 per cent of the original porosity remained. Here a gran- 

 ule which was originally an aggregate of small polymers riddled 

 with openings has been converted into a completely polymerized 

 unit by partial vitrification. 



The behavior of carbon may also be explained on the above 

 assumption. It is known that a dense charcoal subjected to a 

 prolonged heating in the presence of a small amount of oxygen 

 or when treated for a shorter time with superheated steam has 

 its adsorptive power greatly increased. Many writers have 

 thought that this activation resulted mainly from the expulsion of 

 the residual hydrocarbons of the raw charcoal, but this assump- 

 tion is open to the objections, (1), that the small amount of vola- 

 tile hydrocarbon which is left to be expelled is disproportionate to 

 the result produced; (2), that the presence of oxygen though 

 helping to break up the hydrocarbons would not be essential to 

 their ejection, and, (3), the fact that a temperature exceeding 

 1000° C. is needed before they would be all expelled does not 

 square with the theory, if as is usually stated, a temperature from 

 350° to 450° C. is the optimum for air activation. The more prob- 

 able explanation is that a highly polymerized substance like car- 

 bon is likely to be simplified by heating. It is found, however, 

 that heating to 1000° alone has no permanent effect ; the simplifi- 

 cation resulting from the raising of temperature is followed by 

 a reunion on cooling. But if a little oxygen either from air or 

 from steam is available when the polymers are split, a portion of 

 the carbon is removed as C0 2 , and their cleavage is perpetuated. 



Obviously oxygen would not serve the same useful purpose in 

 the case of silica, but here the preparation of the silica from the 

 hydrogel by heating involves the driving off of water which is 

 for the most part chemically combined with the silica and the 

 process will tend to break up the polymers. — Proc. Roy, Soc. 100, 

 88, 1921. f. e. b. 



6. Tables Annuelles de Constantes et Donnees Numeriques ; by 

 the C omite international de I'TJnion de Chimie pure et appliquee. 

 Vol. IV, Part I. Pp. XXII, 626. Paris, 1921 ( Gauthier- Villars 

 et Cie.) . — The present volume contains the determinations of phy- 

 sical constants as abstracted from researches which appeared dur- 

 ing the years 1913-1914-1915-1916, and is published with finan- 

 cial aid from a large number of scientific societies throughout the 

 world. 



Without sacrificing anything of their purpose to make the 

 tables complete, the editors have wisely exercised their discretion 

 in making useful condensations and omitting results which were 

 obtained under uncertain or ill-defined conditions, but including 



