JbLV 20, 1905] 



NA rURE 



277 



In the Proceedings of the Awcricau AcadcDiy of Arts 

 and Sciences (vol. xl., No. 23) Mr. Gilbert X. Lewis 

 makes a study of the auto-catalytic decomposition of silver 

 o.\ide under the influence of heat. It is shown that the 

 velocity of decomposition of the oxide at a constant 

 temperature increases as the action proceeds, and, after 

 passing through a maximum, falls gradually to zero. The 

 phenomenon is due to the catalytic action of the metallic 

 silver produced, the action proceeding very regularly accord- 

 ing to an equation representing the simplest case of auto- 

 catalysis. During the decomposition, definite temperatures 

 between 327° C. and 353° C. were maintained by means 

 of a thermostat containing a fused mixture of sodium and 

 potassium nitrates. The purity and method of preparation 

 of the silver oxide have a very great influence on the 

 velocity of decomposition. The theory is advanced that 

 the influence of the silver is directed in modifying the 

 velocity of the reversible change OjZI^ 2O. 



We have received from the Medical Supply -Association 

 a pamphlet dealing with the Gaiffe auto-motor mercury-jet 

 interrupter and its application in producing high-frequency 

 currents. The interrupter is a simplified form of the 

 mercury-jet turbine type, and is so arranged that the 

 interrupter cuts off the current for both the motor and 

 coil. The interrupter thus works automatically, and the 

 use of an independent motor is dispensed with. The 

 arrangement is simple, portable, and less expensive than 

 any other form of turbine interrupter. 



So.ME singular results obtained during the investigation 

 of the activity of radiotellurium (polonium) are recorded 

 by Prof. B. Walter in a paper in the Annalen der Physik 

 (vol. xvii. p. 367). It would appear that the o rays of 

 radiotellurium are capable of producing a species of 

 fluorescence in the air through which they pass in such 

 a manner that a radiation is set up having a pronounced 

 photochemical action and similar properties to the ultra- 

 violet portion of the spectrum lying between A 350 and 

 K 290. The radiation is completely absorbed by aluminium 

 foil o-oogi mm. in thickness, but readily passes through a 

 glass plate 0-15 mm. thick. In passing through a vacuum, 

 however, the a rays of radiotellurium do not give rise to 

 a radiation, whilst in gases other than air or nitrogen the 

 effect is only very slight. The new radiation seems, 

 indeed, to be produced only by nitrogen, the effect with 

 this gas being thirty to fifty times as great as with 

 hydrogen or oxygen. This fact is of unusual significance 

 as tending to throw light on some of the peculiar properties 

 of the nitrogen atom. 



The part played by the copper salt in Deacon's process 

 of preparing chlorine from hydrogen chloride is still un- 

 certain, although many hypotheses have been put forward 

 to explain it. That which has been most generally adopted 

 assumes that cupric chloride is decomposed into cuprous 

 chloride and chlorine, and that the cuprous chloride then 

 undergoes re-conversion into the cupric salt under the in- 

 fluence of oxygen and hydrogen chloride, copper 

 oxychloride being formed as an intermediate product. In 

 an experimental investigation of the process published by 

 M. G. Levi and V. Bettoni in the Gazzetta (vol. xxxv. 

 p. 320) it is shown, however, that neither cuprous chloride 

 nor the oxychloride can be used with a successful result in 

 Deacon's process, and that the oxychloride is not con- 

 vertible by hydrogen chloride into cupric chloride under 

 the conditions in which chlorine is ordinarily formed. The 

 hypothesis of an intermediate product is rejected and a 

 purely catalytic action assumed, according to which the 

 NO. 1864, VOL. 72] 



velocity of the change 2HCI + -5 = H.O-l-Clj is greatly 



influenced by the presence of the copper salt. The catalyst 

 is supposed to help the action by its tendency to combine 

 with the water produced in the change. 



An interesting article by M. Albert de Ronieu on the 

 industry of the abrasive materials such as corundum, 

 emery, and carborundum appears in the Revue generate 

 dcs Sciences for June 15. 



No. 6 of vol. ii. of Le Radium contains a useful article 

 by M. G. H. Niewenglowski on the development of photo- 

 graphic plates which have been subjected to the action of 

 radio-active substances. 



Under the title " From the Borderland between 

 Crystallography and Chemistry," an address delivered 

 before the Science Club of the University of Wisconsin 

 by Prof. Victor Goldschmidt, of Heidelberg, is printed in 

 the Bulletin of the university (No. 108). Attention is 

 directed to the interesting results that have been obtained 

 by studying the etch-figures and dissolution bodies of 

 crystals and their significance in forming a mechanical 

 theory of dissolution. 



The sugar and cacao industries in the West Indies 

 formed the principal subjects of discussion at the agri- 

 cultural conference held in Trinidad in J'anuary ; the pro- 

 ceedings in connection with these matters are reported in 

 the first number of vol. vi. of the West Indian Bulletin. 

 The condition ot the sugar industry in Trinidad evoked 

 considerable discussion, the subject at issue being the 

 small amount of cane produced by the farmers per acre. 

 Dr. F. Watts gave some account of the establishment of 

 a well equipped central sugar factory in Antigua. The 

 question of shade trees for cacao was debated, but evidence 

 was not forthcoming to show why the shade that is con- 

 sidered necessary in Trinidad proves to be injurious in 

 Grenada. Mr. L. Lewton-Brain and Mr. H. A. Ballou 

 presented papers on the fungoid diseases and insect pests 

 of sugar canes and cacao trees. 



The route followed by Mr. B. Fedtschenko on his 

 botanical journey through the Pamirs, as described in the 

 Bulletin du Jardin imperial botanique de St. Petersbourg, 

 vol. v., lay along the river Pianj where it runs parallel 

 and a little to the north of the boundaries of Kashmir 

 and Chitral ; thence proceeding north the explorer returned 

 to Osch, in Turkestan. .inaphalis seravschanica and 

 Ferula gigantea were the most remarkable plants obtained 

 on these stages of the journey. A malformation of the 

 flowers of Tragopogon pratensii showing pedicelled florets 

 and phyllody of the caly.x is described by Mr. Dmitriew. 



Mr. p. H. Rolfs presented the first results of his in- 

 vestigations into the diseases of citrous plants and fruits 

 caused bv the fungus Colletotrichum gloeosporioidcs in 

 Bulletin No. 52 of the Bureau of Plant Industry, U.S.A. 

 It is there shown that wither-tip, leaf-spot, anthracnose, 

 and fruit canker are all due to the same fungus. Wither- 

 tip and leaf-spot can be controlled by pruning followed 

 by spraying with Bordeaux mixture, while spraying with 

 ammoniacal solution of copper carbonate is efficacious 

 against disease of the fruit. .\ later article in the Florida 

 Agriculturist (March) deals with the appearance of these 

 diseases on grape fruit. 



The Jamaica Bulletin of Agriculture (May) contains an 

 article by Mr. Fawcett on Raiffeisen agricultural banks, 

 prompted by conditions which suggest that such a system 

 could be advantageously introduced into the island. The 



