320 SECTIONAL TRANSACTIONS.— B. 



concentrated nitric acid and ammonia. Four alternative formulae are suggested, 

 namely, C20HS1N.2O3, C20H3.2N2O3, C21H31N2O3, and C21H32N2O3. It is not identical 

 with strychnine or with any of the known strychnos alkaloids, and is apparently a 

 new compound. 



Prof. G. H. Stanley. — The Corn-position of some Prehistoric South African 

 Bronzes, with Notes on the Methods of Analysis. 



This paper puts on record in tabular form the results of chemical analysis and 

 microscopic examination of over 30 examples of S. African pre-historic bronzes, coppers 

 and tins. 



The special methods of analysis necessitated by the small quantities of sample 

 usually available are also described. 



Thursday, August 1. 



Mr. A. C. G. Egerton, F.R.S. — The Influence of Antiknocks on the Combus- 

 tion of Hydrocarbons. 



The theory that antiknocks have their specific effect during the early stages of 

 the inception of combustion by the interruption of the chains of reacting molecules, 

 which has been derived as a result of experiments by Egerton and Gates on the 

 ignition and on the detonation of various mixtures, is further supported by the theory 

 of combustion advanced by SemenofE and, in greater detail, by Thompson and 

 Hinshelwood. 



The effect of pressure on temperature of ignition can be explained in terms of 

 such chain mechanism ; branching of the chains explains the sudden acceleration of 

 rate of combustion resulting in ignition. Some experiments on the ignition points 

 of hydrogen, carbon monoxide and hydrocarbons illustrate this point. 



The effectiveness of various antiknocks are compared by means of a Delco engine 

 designed for the purpose, and the results are reviewed in terms of the above theory. 



Joint Discussion with Section A {q.v.) on Quantitative Chemical Analysis 

 by X-Rays and its Applications. 



Friday, August 2. 



Prof. H. Bassett and Mr. R. G. Durrant. — The Inter-relationships of the 

 Sulphur Acids. 



The hydrogen ion concentration plays a very important part in all reactions of 

 the sulphur acids and in great measure determines the path followed. Addition of 

 acid favours reactions which remove hydrogen ions, in accordance with the principle 

 of Le Chatelier, whilst alkali produces exactly the opposite effect. 



Hydrolysis of sulphur according to the reaction — 



S2+2HOH ';^ H2S + S(OH)2 



and three alternative modes of decomposition of thiosulphuric acid are the key 

 reactions in the chemistry of the sulphur acids. Of these three modes of 

 decomposition 



(1) 2H,S.,03"^S, + 2HS03H 



(2) 2H,S203 ;^ H,S +H2S3O, 



(3) 2H2SAlt;H20+H2SA 



