406 



NATURE 



[June 19, 19 13 



humidity, and wind in his discussion. He finds that 

 the change in the loss by evaporation under different 

 conditions is proportional to the product of the abso- 

 lute temperature and the absolute dryness or satura- 

 tion deficit, and he makes the interesting suggestion 

 that sufficient observational results should be obtained 

 to give normal values for the constants for different 

 sexes, races, &c. Incidentally the paper emphasises 

 the importance of the wet-bulb temperatures as a 

 climatic factor, especially in tropical or semi-tropical 

 regions. It may be noted that experiments on the 

 effect of different meteorological conditions on the 

 human body are being conducted by Dr. J. R. Milne 

 at Edinburgh, a preliminary account being given in 

 the recently issued Journal of the Scottish Meteoro- 

 logical Society. 



The Meteorological Institute of the Netherlands 

 has issued copies of thirteen of the principal mag- 

 netic disturbances of the year ign, as recorded at 

 de Bilt, and the director of the institute, Prof, van 

 Everdingen, intimates that in future it is intended 

 to publish each year copies of the chief disturbances, 

 as indicated on the international lists compiled under 

 his auspices. The time scale adopted is 15 mm. to 

 the hour, and the curves — declination, horizontal 

 force, and vertical force — are very clearly reproduced. 



We have received a copy of an address delivered by 

 Dr. Wolfgang Ostwald before the eighty-fourth Ver- 

 sammlung Deutscher Naturforscher on " Die neuere 

 Entwicklung der Kolloidchemie " (pp. 23, T. Stein- 

 kopf, Dresden, price 1 mark). Colloid-chemistry is a 

 branch of science which has made striking progress 

 during the past few years, and has now not only a 

 distinct terminology of its own, but a journal, the 

 Kolloid-Zeitschrift, to chronicle its advances. The 

 brief review given by Dr. Ostwald of recent develop- 

 ment of the science should prove of interest to many 

 workers in the numerous fields of science and industry 

 in which a knowledge of colloids is of importance. 



We have received a copy of the Compte Rendu of 

 the Geneva Physical and Natural History Society for 

 the year 1912. The society has sixty-eight ordinary 

 and forty-two honorary members, and admits twenty- 

 eight associates free. The Compte Rendu extends to 

 more than eighty pages, and contains articles on 

 physics, chemistry, botany, geology, and zoology of 

 considerable interest. Amongst the most important 

 of these articles are Prof. Guye's on the internal 

 friction of metals at high and at low temperatures, 

 and M. Tommasina's surveys of Ritz's theories of 

 the asther and of gravitation. 



The June number of Terrestrial Magnetism and 

 Atmospheric Electricity contains a list of the deter- 

 minations of declination made on the magnetic survey 

 ship Carnegie during its voyage across the Pacific 

 from Tahiti, Society Islands, to Chile, and thence vid 

 Cape Horn to the Falkland Islands. Comparisons are 

 made between the values obtained and those given 

 on the United States, the German, and the British 

 charts. So far as the latter is concerned, the cor- 

 rections to be applied to the charted values are in most 

 NO. 2277, VOL. 91] 



cases less than one degree, but exceed that amount 

 at nine points off the coast of Chile and Patagonia, 

 where the chart shows the easterly declination too 

 small. 



In a paper recently published in the Bulletin of the 

 Imperial Academy of Sciences of St. Petersburg, Prof. 

 P. Walden brings forward additional evidence in 

 favour of the view that the degree of dissociation of 

 a given solute is independent of the nature of the 

 solvent if each solution is at the saturation point. 

 This was demonstrated previously for tetramethyl- 

 ammonium iodide, N(C,H 5 ). 1 I, in fourteen solvents, 

 but is now shown to be true for tetramethylammonium 

 iodide, N(CH 3 ),I, in ten solvents (a = o-666), for tetra- 

 propylammonium iodide, NfC^H,).,!, in five solvents 

 (0 = 0-26), and, finally, for potassium iodide, KI, in 

 three solvents (0 = 0-423). 



In the May issue of the Chemical Society's Journal 

 Dr. Scott describes some new methods for the pre- 

 paration of pure bromine. The first method depends 

 on getting rid of iodate and iodide by boiling potass- 

 ium bromide with a little potassium metabisulphite 

 and sulphuric acid, then twice adding saturated 

 bromine water and distilling off the bromine, and 

 finally neutralising with potassium carbonate and 

 evaporating to dryness. The bromide was then fused 

 with potassium dichromate in quantity insufficient to 

 decompose any chloride that might be present ; the 

 fused mass was decomposed by sulphuric acid with 

 the addition of a little permanganate to decompose 

 organic matter. A quantity of 3250 grams of pure 

 bromine was prepared in this way, together with an 

 additional 185 grams, which should contain all the 

 chlorine, but this was found to amount only to 4 or 5 

 milligrams. The halogen impurities were separated 

 by extracting the bromine with caustic soda ; this 

 appears to provide a very simple and a most effective 

 way of purifying bromine, the chlorine being removed 

 as chloride, and the iodine as iodate. By this method 

 the whole of these halogens can be removed from 

 10 c.c. of bromine by extracting once with 5 c.c. of 

 normal sodium hydroxide. 



OUR ASTRONOMICAL COLUMN. 



Observatories and Cities. — Modern astronomical 

 research work, which necessitates the long exposure 

 of photographic plates and the observation of faint 

 stars, is gradually separating old observatories from 

 their historic surroundings and creating new build- 

 ings in more favourable situations. The Hamburg' 

 Observatory is now settled in its new site in Berge- 

 dorf, some distance away from the city, and the new- 

 ground is bristling with domes of the latest construc- 

 tion. Berlin Observatory is now on the move, taking 

 up its new position in Neu Babelsberg, not very far 

 from its astrophysical confrere at Potsdam. At the 

 present time the question is being considered as to the 

 removal or part removal of the Paris Observatory, 

 as the conditions on the site now occupied are not 

 conducive to the best observational work. Those un- 

 familiar with the present locality can obtain a good 

 idea of it in relation to Paris from the excellent re- 

 production of a photograph by M. Baillaud which is 

 given in the current number of The Observatory (June, 

 No. 462). 



