SECTIONAL TRANSACTIONS.— B, C. 313 



Dr. H. T. S. Britton ; Dr. R. A. Robinson, and Mr. W. L. German. — 



Complex Acids of the Rarer Elements. 



After briefly referring to electrometric titrations — potentiometric and conducto- 

 metric — of normal monobasic and polybasic acids, it is shown how these methods have 

 been applied to the study of tungstic, molybdic and vanadic acids. The work so far 

 done reveals that these acids are by no means similar to the corresponding acids 

 formed by the earlier members of groups 5 and 6 respectively of the periodic classi- 

 fication as regards their electrolytic dissociation and chemical behaviour. It is a 

 surprising fact that the tungstic and vanadic oxides are not readily precipitated from 

 solutions of their salts on acidification in spite of their almost complete insolubility in 

 water. The observations indicate that there are present in acid solutions alkali metal 

 salts of ill-defined polyacids, which tend to resist decomposition except by a large 

 excess of acid. 



Dr. F. G. SoPER. — The Effect of the Solvent on Reaction Velocity. 



The relation of reaction speed in solution to the cohesion of the solvent and to the 

 relative cohesions of the products and reagents (Richardson and Soper, J. C. S., 1929, 

 1873) may be explained in terms of a solvent effect on the critical complex, controlling 

 the proportion of critical complexes breaking up to form the reaction products. 



By using the velocity equation for a homogeneous gas reaction to express the rate 

 at which critical complexes are produced and by assuming that the fraction of com- 

 plexes breaking up to form the products is connected with the relative entropies of 

 reagents and products, a reaction velocity equation is obtained which is in conformity 

 with the equilibrium requirements and which also expresses the connection between 

 reaction speed and the cohesion of the solvent. 



Afternoon. 

 Visit to the National Smelting Co., Ltd., Avonmouth Factory, Avonmouth. 



SECTION C— GEOLOGY. 



Thursday, September 4. 



Prof. S. H. Reynolds, Mr. J. W. Tutcher, and Prof. L. S. Palmer. — 

 The Geology of the Bristol Area. 



Mr. E. H. Davison. — The Granite of Western Cornwall, its Alteration 

 and Contact Metamorphism. 



In the paper West Cornwall is taken as that part of the county from Land's End 

 to east of the Hensbarrow or St. Austell granite outcrop. The various granite out- 

 crops inside this area are considered to be the denuded cupolas of an underlying mass 

 of potash granite which, though showing a certain amount of variation in composition, 

 is believed to be one intrusion. 



The sequence of events was : — • 



(a) emplacement of the granite mass, 



(6) intrusion of pegmatite, aplite and ' elvans ' (quartz porphyries of various 

 types), 



(c) uprise of fluids charged with compounds of boron and fluorine. 



The alteration of the country-rocks (chiefly slates) is due to (a) and (c). In the 

 aureoles the slates show the following changes as the granite is approached : 



(a) spotting, 



(b) development of chiastolite, andalusite or ottrelite, 



(c) development of micas, 

 {d) conversion to hornfels. 



Basic dykes and sills have also been made into epidiorites. 



