540 SCIENCE PROGRESS 



able, this being responsible for the low heat of combustion of 

 the diamond, 



2 - 2 y = 94*4 Kcal, 



as compared with that of the carbon in aliphatic compounds 

 viz. 101-105 Kcal. Hydrocarbons with side- chains contain 

 more of the subsidiary — C — C — linkings, and it would be 

 expected that their heats of formation would be higher and their 

 heats of combustion lower than those of the isomeric straight- 

 chain compounds. These and other similar relationships are 

 found to hold. 



Oxidation of Phosphorus. — Weiser and Garrison (/. Phys. 

 Chem., 192 1, 25, 473) have shown that the first step in the 

 oxidation of phosphorus is the formation of phosphorus tri- 

 oxide, and that this reaction takes place at a lower temperature 

 than that of the further oxidation to the pentoxide. The for- 

 mation of the pentoxide is accompanied by the emission of 

 light, and the action of inhibitors destroying this luminescence 

 is due to a retardation of this reaction. Positive catalysts like 

 ozone, nitrobenzene, etc., react energetically with the trioxide, 

 giving rise to an increased luminosity, while negative catalysts, 

 being adsorbed on the surface of the trioxide, have a reverse 

 effect. A stream of pure oxygen at 27° C. converts the vaporised 

 phosphorus to the trioxide, which may be made to oxidise with 

 luminescence by raising the temperature of the mixture. Ozone 

 is formed during the latter change. Lord Rayleigh {Proc. Roy. 

 Soc, 1921, A. 99, 372), in a series of striking experiments, shows 

 that the percentage of water present in the oxidation of phos- 

 phorus is important ; air dried over suphuric acid does not 

 inhibit the glow of phosphorus, but the presence of greater 

 amounts of water produces a periodic luminosity. The glow 

 travels like an explosion wave through the air saturated with 

 phosphorus when sufficient water vapour is present. Small 

 quantities of other inhibitors, such as turpentine, produce 

 similar effects. When these are present in excess, the glow 

 is completely extinguished. 



Isotopes. — Bronsted and Hevesy (Phil. Mag., 1922, 43, 31) 

 have succeeded in partially separating mercury into its isotopes 

 by evaporation and effusion methods. A separation corre- 

 sponding to a difference of ci unit in the element weight of 

 mercury has been obtained. Harkins and Hayes {J.A.C.S., 

 1 92 1, 43, 1803) give an account of further experimental work on 

 the separation of chlorine into its isotopes by the diffusion of 

 hydrochloric acid gas. An increase in the atomic weight of 

 chlorine of approximately one part in a thousand has been 

 obtained. 



Lazv of Distribution of Colloidal Particles in Colloidal Solu^ 



