424 



NA TURE 



[August 31, 1893 



upon the meteorological instrumentsat the exhibition, and though 

 there was a difficulty in comparing objects in the same class, 

 owing to their being distributed over an immense area, it was 

 satisfactorily overcome. Meteorologists will be glad to know 

 that Mr. Retch's report has been extracted from the second 

 volume of the Reports of the U.S. Commissioners to the 

 Universal Exposition at Paris, and is now issued separately. 



The report on the operations of the Department of Land 

 Records and Agriculture, Madras Presidency, for the official 

 year 1891-92 has been received. From it we learn that ex- 

 periments made by the Madras railway companies in the use 

 of eucalyptus leaves to prevent incrustation in locomotive 

 boilers have turned out very satisfactory, and are therefore being 

 continued. The chief feature of the year was the comparative 

 immunity from serious disease which the cattle enjoyed. The 

 total reported losses (87,000) were only fifty-eight per cent, of 

 the average losses, and fifteen per cent, less than in 1890-91. 

 The losses from snake-bite decreased from 2,698 to 1,751, and 

 the decrease was spread over the whole Presidency, except 

 Ganjam and Vizagapatam. Losses by wild animals also de- 

 creased by 345 head. No reason is given to account for this 

 singular reduction. 



The Royal Society of Tasmania issued in June last the re- 

 ports of its proceedings in 1892, and the volume has just 

 reached us. Among other papers printed in full occurs one by 

 Mr. G. M. Thomson on Tasmanian Crustacea, with descriptions 

 of new species, and another on new species of Tasmanian 

 aranes, by Mr. A. T. Urquhart. The Rev. F. R. M. Wilson 

 contributes a paper on the climate of Eastern Tasmania, indi- 

 cated by its lichen flora, in which he gives facts which "sug- 

 gest to the medical faculty what probably their experience has 

 already proved, that the climate of East Gippsland and the 

 eastern coast of Tasmania must be pre-eminently beneficial to 

 invalids. Lichenological observations indicate that both of 

 these places are favoured by a much milder winter, as well as a 

 cooler summer,than the other parts of their respective colonies." 

 Mr. Wilson also gives a description of Tasmanian lichens, and 

 Mr. John Shirley a list of those now known. 



Dr. D. S. Jordan showed in 1889 that, in every case where 

 the waters of Yellowstone Park were destitute of fish, the cause 

 was topographical, that is to say, there was some physical 

 barrier to the entrance of fishes from below. This being so, it 

 seemed possible to stock these waters permanently with game- 

 fish, so the U.S. Commissioner of Fish and Fisheries sent 

 Prof. S. A. Forbes to Yellowstone Park in 1890 to investigate 

 the variety and abundance of the lower animal life of the Ashless 

 waters, since upon this the fishes introduced would chiefly have 

 to depend for food. Prof. Forbes has prepared his " Prelimin- 

 ary Report on the Aquatic Invertebrata Fauna of the Yellow- 

 stone National Park, Wyoming, and of the Flathead Region of 

 Montana." In it he presents .1 summary review of the inver- 

 tebrate life of the waters of Wyoming and Montana in the mid- 

 summer season, with descriptions and determinations of such 

 new or particularly abundant kinds as have thus far been made 

 o'tit. A detailed discussion of the results will be published as 

 soon as the mass of material collected during the expeditions 

 has been examined. 



The organometallic compounds of magnesium form the sub- 

 ject of a communication to the current number of Liebig's 

 Annalen by Dr. Fleck of Tubingen. The di-methyl, di-ethyl 

 and di-propyl compounds of magnesium were obtained by Dr. 

 Lohr in the same laboratory in 1890. Dr. Fleck has continued 

 the work, and now describes the di-phenyl compound and gives 

 further details concerning the mode of preparation and pro 

 perties of the fatty alkyls above mentioned. The magnesium 

 NO. 1244. VOL. 48] 



alkyls are of a somewhat similar nature to the well-known zinc 

 methide and ethide. They differ, however, in the nature 

 certain of their reactions, and their chemical activity is consider, 

 ably superior to that of the zinc alkyls, which have hitherto been 

 regarded as exceptionally active substances. Not only are the 

 magnesium compounds spontaneously inflammable in the air, 

 but the methyl compound was described by Dr. I.ohr as ignit- 

 ing spontaneously and burning in a very beautiful manner in 

 carbon dioxide gas, being capable of extracting the oxygen from 

 its combination with carbon. The three fatty alkyls are best 

 prepared by the action of the alkyl iodides upon magnesium 

 amalgam. When an attempt, however, is made to prepare the 

 diphenyl compound by heating in a closed and previously 

 exhausted tube a quantity of magnesium amalgam and brom- 

 benzene, instead of obtaining magnesium diphenyl decomposition 

 occurs, and the resulting product is merely a mixture of bromides 

 of magnesium and mercury with diphenyl itself (CgHs)^. Dr. 

 Fleck has at last succeeded in preparing magnesium diphenyl 

 by heating a mixture of magnesium filings and mercury diphenyl, 

 Hg(C6HB)2, within a narrow range of temperature. About ten 

 grams of mercury diphenyl and a little more than the calculated 

 quantity of magnesium in fine powder are placed in a tube of 

 soft glass, which is then exhausted by means of the air pump 

 and sealed. Upon heating the tube and contents to ::oo a 

 violent reaction suddenly occurs, with production of a voluminous 

 white mass occupying at least three times the space of the 

 original mixture. Above 210° this white substance commences 

 to carbonise, so that the tube is maintained for four or five hours 

 at a temperature of 200 — 210°, not exceeding the latter limit. 

 The product is spontaneously inflammable in air, so that it is 

 necessary to open the tube under benzene. Any excess of 

 mercury diphenyl is dissolved out by warming with benzene 

 over a water bath, the residue is then treated with a mixture of 

 ether and benzene, in which alone of all the organic solvents 

 tested magnesium diphenyl is soluble ; upon decantation from 

 the residual amalgam and evaporation of the clear liqu d in a 

 stream of nitrogen, pure magnesium diphenyl is obtained as a 

 grayish-white solid. Analyses of ihe product agree with the 

 formula Mg(CjH5)2. 



Magnesium diphenyl, like the dimethyl, diethyl and diprop^ 

 compounds, reacts in a most violent manner with water. EveB 

 when the substance is first covered with ether, and then smalt 

 pieces of ice are slowly added, the reaction still occurs almost 

 explosively. Magnesium hydrate and benzene are the products 

 of the reaction as indicated by the equation 



Mg(CeH.,), -f 2H2O = Mg(OH), + zC^W^. 



Magnesium diphenyl is consequently extremely hygroscopis^ 

 attracting moisture from the air with great rapidily when covereJ 

 wilh a layer of benzene. When freely exposed to the air it at 

 once burns to magnesium oxide and a carbonaceous mas5. If, 

 however, the compound is covered with benzene and exposed 

 to perfectly dry air for some days, an oxy-compound, Mg(OC5H5)j 

 is formed as a brown solid. Bromine reacts with great enei^y 

 to form bromides of magnesium and phenyl, even when largely 

 diluted with ether, and so does not form an intei mediate com- 

 pound, 



yBr :' 



Mg: 



CaH. 



corresponding to the well-known zinc iodoethide, 



"\ 



C0H5 



Indeed, this incapability of forming mixed halogen alkyl?, owing 

 to greater activity, is one of the most characteristic distinctions 

 between the magnesium and the zinc alkyls generally. Benzal 



