November 14, 19 12] 



NATURE 



319 



Dr. C. H. Desch gave a brief summary of a very 

 full report he has prepared on diffusion in solids, 

 which was in print before the meeting. The final 

 conclusion is that the occurrence of diffusion in metals 

 is established beyond any doubt, but that experiments 

 are still lacking to prove its occurrence in transparent 

 crystals of minerals, salts, or organic substances. 

 The report deals with diffusion in glass, the passage 

 of gases through metals, and particularly with 

 diffusion in solid metals, including cementation and 

 decarburisation of iron. Dr. Holt followed with a 

 paper on the sorption of hydrogen by palladium, in 

 which he described his own recent experimental work. 



The next paper, by Mr. R. de J. Fleming-Struthers, 

 dealt with nitrogen chloride in relation to photo- 

 chemical inhibition. When nitrogen chloride vapour, 

 mixed with an indifferent gas, is heated, no change 

 is perceptible until the temperature reaches a certain 

 value ; then suddenly decomposition begins and 

 appears always to culminate in an explosion. Ex- 

 plosion likewise occurs in an atmosphere of hydrogen, 

 but in this case an interaction sets in, and ammonium 

 chloride is precipitated. When a similar mixture is 

 exposed to the action of light, only very little of the 

 nitrogen chloride is converted into ammonium 

 chloride, showing that practically all the nitrogen 

 chloride is decomposed by licfht before any hydrogen 

 chloride can be formed. Nitrogen chloride is an 

 inhibitor of combination between chlorine and 

 hydrogen on exposure to light, and is capable of 

 producing a period of inaction comparable to Bunsen 

 and Roscoe's induction period. 



Mr. A. Fleck gave an account of a careful chemical 

 examination of Marckwald and Keetman's statement 

 that thorium and uranium X could not be separated. 

 This has been confirmed, the method chiefly used 

 in the attempted separation being fractional precipita- 

 tion. It was found impossible to alter the concen- 

 tration of the short-lived radio-active element in 

 thorium. Similarly radio-actinium and thorium, 

 also thorium B and lead, were found to be two pairs 

 of chemically inseparable elements. 



.A paper bv Prof. Stock (Breslau) and Dr. G. E. 

 Gibson on the dissociation of phosphorus vapour may 

 be referred to here, though it was read on the 

 Monday. The authors have determined the pressure 

 temperature curves of phosphorus vapour at various 

 volumes, using quartz apparatus and a new form of 

 quartz membrane manometer devised bv Gibson. I'p 

 to 700° C. the vapour density, corresponds to the 

 foimula P^. .Above this, dissociation takes place 

 according to the equation P, = 2P„. 



On the Friday the section joined with the botanists 

 to discuss questions of chemical variation in plants 

 and the nature of plant pigmentation. 



Dr. J. V. Evre gave an account of work carried 

 out with Prof. H. E. Armstrong on the enzymes 

 and glucoside of flax. The glucoside linamarin is 

 constantly present in the green plant and in the 

 unripe seed of flax ; in consequence, hydrogen cyanide 

 can usually be detected in commercial linseed cake. 

 Ripe seeds are free from cyanide, but since flax 

 flowers during a considerable period, the seeds are 

 never ripe all at once. In extreme cases the amount 

 of hydrogen cyanide may be sufficient to be harmful, 

 but it is also probable that it is of positive condi- 

 mental value, and that the special value of linseed 

 cake as a cattle food may be due in part to the 

 liberation of minute proportions of hydrogen cyanide. 



In addition to common flax, a wide variety of 

 Linaceae have been tested; only the w-hite, blue, or 

 red-flowered varieties contain the glucoside, which 

 is entirely absent in all the yellow flowering species 

 examined. Dr. Eyre also gave an account of the 



NO. 2246, VOL. 90] 



variations in the flax plant with locality, flax being 

 a plant which rapidly becomes adapted to new con- 

 ditions. Seed taken from a blue flowering crop is 

 commonly stated to give a crop of flax bearing white 

 flowers when raised under different conditions of 

 climate. A number of similar instances of degenera- 

 tion were noted. In the discussion Prof. Bateson 

 expressed the opinion that it should not be difficult 

 to select a type of flax which would breed true for 

 any desired qualities. Probably the commercial seed 

 was impure, so that under changed conditions a 

 previously minor constituent of the mixture was un- 

 duly favoured. This would account for much of the 

 variation mentioned. 



Prof. Armstrong gave an account of the variation 

 of glucoside and enzyme in Lotus cornicidatus, which 

 has been studied over a wide area. The glucoside 

 of this plant contains hydrogen cyanide, and is prob- 

 ably identical with that present in flax. Whereas in 

 19 10 plants collected near Reading contained the 

 glucoside, it was, as a rule, missing from plants 

 gathered in other localities. During 19 ii cyanide 

 was found uniformly present in plants from different 

 parts of England, but it was frequently absent in 

 specimens from the west of Scotland and from 

 Norway. Variation in the age or habit of the plant 

 or in the nature of the soil had no effect on the 

 presence of cyanide. The glucoside was always 

 accompanied by the appropriate enzyme, whereas in 

 the allied species L. major neither enzyme nor gluco- 

 side ever occur. This paper was very fully discussed 

 by Prof. Bateson and the botanists present, and it 

 was regarded as a significant case of chemical varia- 

 tion in plants which requires further study. 



A joint paper on the biochemistry of plant pig- 

 mentation by Prof. F. Keeble and Dr. E. F. 

 Armstrong was read by the latter, who gave a general 

 summary of the subject from the chemical side, 

 supplementing that contained in the presidential 

 address to the botanists. It is probable that the 

 soluble sap pigments of plants are formed by the 

 action of an oxydase on a colourless chromogen, 

 which has first to be liberated by the appropriate 

 enzyme from its combination with glupose. It is 

 possible that amino-acids or other protein degrada- 

 tion products take part in the interaction, and that 

 this variable factor accounts for the differences in 

 shade. Methods were described which enable the 

 exact localisation of the oxydases in plant tissues, 

 either macro- or micro-chemically, without any far- 

 reaching breakdown of the cellular structure taking 

 place. It has been possible to show in the clearest 

 manner possible that the localisation of these oxydases 

 in plants agrees closely with that of the colour. 



O.xydases, according to current theory, are supposed 

 to consist of two constituents — a peroxydase and an 

 organic peroxide. Normally the occurrence of the 

 latter is rare, but the authors produced evidence to 

 show- that it increases in amount when a plant is 

 kept in the dark. After such treatment it can be 

 detected in plants from which it was formerly absent. 

 The amount of peroxydase is also increased during 

 the night. These observations give a clu'e to some 

 of the phenomena of periodicity in life. 



Attention w-as also directed to the chemical identi- 

 fication and study of the inhibiting factors in plants 

 and animals to 'which Mendelians attach so much 

 importance. 



Besides the oxydases measured by the authors' 

 methods, evidence is obtained that others are present 

 in plants which may or may not be different. Such 

 become prominent when the plant is wounded or 

 treated with chloroform, with the result that browning 

 or blaclfening takes place. Evidence is being accu- 



