64: 



NA TURE 



[OCTOBKR 26, 1905 



CHEMISTRY AT THE BRITISH ASSOCIATION. 

 HTHE papers contributed to Section B at the meetings 

 ■'■ in Soutli Africa were naturally more limited in 

 number and in range of subject than is usual at ordinary 

 meetings of the association, the majority of the communi- 

 cations having reference either to the chemical aspects of 

 agriculture or to subjects connected with the gold extract- 

 ing industry. On the other hand, a very active part in 

 the work of the section was taken by the South African 

 chemists, and, almost without exception, the reading of a 

 paper was followed by an animated and interesting 

 discussion. 



At Capo Town, the first day of meeting was set aside 

 for the discussion of agricultural and biochemical ques- 

 tions. As it had been arranged that the presidential 

 address should be delivered at Johannesburg, its place was 

 taken by Mr. A. D. Hall's report on recent developments 

 in agricultural science, in which many subjects of special 

 interest in South Africa were discussed. Dealing with the 

 fixation of atmospheric nitrogen through the agency of 

 bacteria, the author pointed out that a sharp distinction 

 must be drawn between the use of pure cultures on old 

 cultivated lands and in new countries, where leguminous 

 crops are often being grown for the first time, and that 

 the behaviour of the lucerne plant under bacterial infection 

 in South African soils is worthy of careful investigation 

 in view of its economic importance in all semi-arid 

 countries. He directed attention to the need of a systematic 

 series of soil analyses, with the ultimate object of making 

 soil maps that shall be of service to the agriculturist, and 

 indicated how much still remains unknown regarding the 

 nutrition of plants and how great is the importance of 

 research in the particular functions of the various con- 

 stituents of the crop, as it is only through such knowledge 

 that the quality of crops may possibly be influenced in 

 desired directions. A brief discussion of the subjects of 

 acclimatisation and cross-breeding brought to a close an 

 address which aroused very great interest. Dr. Horace T. 

 Brown then gave an account of his researches on the 

 assimilatory processes of plants, in the course of which 

 he described his method by which the assimilative power 

 of leaves was measured for the first time under natural 

 conditions. The quantity of carbon dioxide abstracted from 

 the air by leaves of measured area was estimated in a 

 special absorption apparatus devised for the purpose, and 

 thus it was possible to deduce the amount of carbohydrate 

 formed. The total solar radiation falling on the leaf was 

 measured, and the proportion of the radiant energy of sun- 

 light absorbed and transmitted by the leaf was also arrived 

 at. The author's investigations showed that the rate of 

 growth is not entirely dependent upon the amount of 

 sunshine, but also on secondary causes. The business was 

 brought to a close by a short paper by Dr. E. F. Armstrong 

 on the role of enzymes in plant economy, in which the 

 author directed attention to the fundamental similarity 

 between the action of acids and that of enzymes, the dis- 

 tinction between them arising from the fact that enzymes 

 act selectively in consequence of their power of associating 

 themselves with the hydrolyte. The condition of the carbo- 

 hydrate in solution is of primary importance, but this 

 condition may to some extent be determined by the enzyme. 



-At the second day's meeting. Prof. H. B. Dixon gave a 

 historical sketch of researches made on the propagation 

 of explosions in gases, and discussed Berthelot's theory 

 and his own " sound wave " theory on the mode of pro- 

 pagation. With the aid of the lantern he showed how he 

 had followed photographically the flame from its initiation 

 until the setting up of the detonation, and demonstrated 

 the influence of the position of the spark and of the length 

 of the column of exploding gases. He also described 

 experiments now in progress on the specific heats of gases 

 at high temperatures, and explained how the velocity of 

 sound in a heated gas may be determined. In a second 

 paper Prof. Dixon described' the method he has devised for 

 determining the atomic weight of chlorine by the direct 

 burning of a known weight of hydrogen in a known weight 

 of chlorine, the hydrogen, prepared by the electrolysis of 

 barium hydroxide, being occluded in palladium, and the 

 chlorine, prepared by the electrolysis of fused silver 

 chloride, being weighed in the liquid state. The atomic 

 NO. 1878, VOL. 72] 



weight obtained is higher than that of Stas, but in close 

 agreement with the recent results of Richards. Messrs. 

 G. T. and H. \V. Beilby gave an account of their experi- 

 ments on the influence 'of phase changes on the tenacity 

 of ductile metals at the ordinary temperature and at the 

 boiling point of liquid air. They showed that when a wire 

 of ductile metal is stretched to four or five times its 

 original length by drawing it through the holes of a wire 

 plate all the ord'inarv traces of crystalline structure dis- 

 appear, but the wire' still consists of minute granules of 

 the crystalline phase embedded in a matrix of the amor- 

 phous phase. By lowering the temperature of drawing, the 

 mixture appi caches more nearly to the homogeneous 

 amorphous state. Observations were made at 15° and at 

 — 180° on wires of copper, silver, and gold, which had 

 been as completely as possible converted into the amorphous 

 phase by wire drawing at the ordinary temperature, and 

 in every case the tenacity observed was higher than any 

 recorded by previous investigators for equally pure mclals. 

 The wires broken at the ordinary temperature showed no 

 general stretching, but at the boiling point of liquid air all 

 the wires stretched about 12 per cent. Dr. A. Midlay 

 recorded his determinations of the viscosities of liquid 

 mixtures at the temperature of their boiling points, which 

 were made in the expectation that viscosity curves would 

 be obtained similar in form to the boiling-point curves. 

 In the case of benzene and methyl alcohol, the viscosities 

 of which at the respective boiling points are nearly the 

 same, the expectation appears to be realised, but where 

 the viscosities of the pure liquids at their boiling points 

 are not the same certain complications are met with. 



The third day of meeting at Cape Town was set apart 

 for communications from local chemists. Prof. P. D. Hahn 

 gave an account of the remarkable thermal chalybeate 

 spring at Caledon, in Cape Colony. With the aid of a 

 tabular statement of the purity ratio of the most famous 

 chalybeate springs, he showed that the Caledon water 

 holds with the water of Spa the first place, but he pointed 

 out that while the waters of most chalybeate springs arc 

 very low in temperature, the Caledon spring is unique in 

 so far that the temperature of the water at the eye of the 

 spring is 49° C. Mr. C. F. Juritz stated that for various 

 reasons very scanty attention has hitherjio been paid to 

 purely scientific chemical research in Cape Colony, and 

 gave an .interesting account of several investigations made 

 in the Government laboratory under his direction. .\ 

 chemical survey of the soils of the colony (at present 

 suspended for want of funds) has resulted in the examin- 

 ation of an area of 27,000 square miles, on an average one 

 sample being taken for every 60 square miles. A number 

 of the fodder plants of the Karroo have been examined as 

 regards their nutritive value, estimations of tannin in the 

 barks of various trees have been made, poisonous prin- 

 ciples have been extracted from some indigenous plants, 

 and an alkaloid resembling quinine therapeutically, but 

 differing from it chemically, has been extracted from the 

 umjela or quinine tree, which abounds in the Transkei. 

 Clays have been found in various parts of the colony some 

 of which compare favourably in chemical composi- 

 tion with the best fire clays, and mineral pitch has 

 been observed in certain localities. Dr. H. Tietz, in a 

 paper on the character of Cape wines, explained that at 

 the Cape grapes always become perfectly ripe, and thus 

 contain more sugar and less acid than the grapes of the 

 wine-producing countries of Europe. Notwithstanding 

 this, a standing reproach against Cape wines is based on 

 the contention that they contain more acid than European 

 wines. The author investigated this matter on some 300 

 samples of different Cape wines, and found that the 

 allegation cannot be upheld. 



At Johannesburg the proceedings of the section were 

 inaugurated by the delivery of the address of the presi- 

 dent, which was of quite e.xceptional interest. It was 

 followed by a paper by Mr. H. F. Julian, in which an 

 investigation of the part played by oxygen in the dissolution 

 of gold by cyanide solutions was described. The author 

 arrived at the conclusion that free oxygen plays no primary 

 part in the reaction, any assistance given being of a 

 I secondary nature, and that, as a matter of fact, it exerts 

 j a retarding influence. .According to his experiments, while 

 I the balance indicates that free oxygen is of material assist- 



