SECTIONAL TRANSACTIONS.— B. 319 



gallotannins belong the tannins of gallnuts from the different species of oak and 

 sumach. The catecholtannins, derived from catechin, consist of the catechu- and 

 gambier-tannins, quebrachotarmin, &c. The chief properties and uses of these 

 tannins are discussed. 



In the case of other tannins, those of the Middle European oak, the mangrove, 

 the South African sumach from osyris, the cinchona bark, &c., which have been 

 closely investigated, not even the group classification is known. They have, however, 

 certain constitutional features and properties in common on which their industrial 

 uses depend. 



The r61e of each tannin class from the standpoint of plant physiology is discussed. 

 There is the possibility of a relationship between gallic acid and the sugars and the 

 established relationship of catechin to the sap-soluble pigments of the flavone group 

 and to the anthocyanins indicate their connection mth the respiration process. 



The general behaviour of all tannins in plants is the same. Being formed mostly 

 in the leaf cell, they must pass through the membranes in a lower molecular form 

 before being finally deposited in the galls, bark and wood. In the case of the 

 hydrolysable gallotannins this is possible through the hydrolysis products, gallic acid 

 and sugar, which can then reform the gallotannins by condensation. In the case of 

 the non-hydrolysable catecholtannins, the only possibility is for these to be formed 

 from catechin itself, which can pass through the membranes and form the complex 

 catecholtannins later. It is possible that this primary stage of the catecholtannins 

 may be found in the leaves. 



JOHANNESBURG. 

 Wednesday, July 31. 



Mr. H. A. White. — The Chemistry of Gold Extraction. 



The reactions utilised in the extraction of Gold from Banket Ores by the Cyanide 

 Process are briefly discussed and each step in the treatment from the stopes to the 

 Residue Dumps is described from the point of view of the Chemistry involved 

 therein. 



Prof. M. RiNDL. — A Crystalline Alkaloid from the hark of Strychnos 

 Henningsii. 



Whilst the bark of most strychnos varieties is poisonous that of Strychnos 

 Henningsii is either non-toxic or only slightly so. It contains between 5 and 6 per 

 cent, of alkaloid, and is ' reported as being used by the natives of Eastern Pondoland 

 as an appetiser-bitter extracted in alcohol.' It is also reputed to be endowed with 

 medicinal virtues. It is known locally as the ' hard pear tree.' 



On the initiative of the Forest Department of the Union an investigation into the 

 active constituents of the bark was begun at the Imperial Institute, South Kensington, 

 in 1913, by Mr. A. E. Andrews, but had to be abandoned before completion on account 

 of the war. Whilst he could obtain the bulk of the alkaloid only in the form of a 

 resin, he succeeded in isolating a small amount of a crystalline base. The 

 investigation was continued by the author with fresh supplies of plant material. 



It transpired that there was some doubt about the botanical identity of the original 

 plant material as it had been ascertained in the meantime that a species, Strychnos 

 initis, which is closely allied botanically to S. Henningsii, occurs commonly in the 

 indigenous forests of South Africa. Supplies of Strychnos mitis bark were accordingly 

 obtained, but proved to be practically devoid of any constituents of an alkaloidal 

 nature. Repeated attempts to obtain further supplies of the alkaloid originaUy 

 isolated by Andrews ended in failure. Success was finally achieved with bark 

 collected at approximately the same period as that originally sent to the Imperial 

 Institute, and the suggestion is put forward that seasonal variations may account 

 for the presence of the alkaloid in some consignments of the bark and its absence in 

 others. The crystaUine alkaloid is obtained by repeatedly shaking an acid aqueous 

 Solution of the total alkaloids with chloroform. It is gradually and seemingly 

 continuously removed from the solution by this method, indicating feeble basicity. 



It melts at 280.5-282° C, is not alkaline to litmus, crystallises from alcohol in 

 tabular crystals of the rhombic system and gives characteristic colour reactions with 



