SH 



NATURE 



\Feb. 17, 1876 



condition. For the examination and description of these col- 

 lections I wish to employ the younger scientific men of eminence 

 in our country, and as the most of them cannot without too great 

 a sacrifice undertake year-long labours more or less foreign to 

 their proper employment, I have made an application to the 

 Government for a grant of 10,000 crowns (about 550/.) to defray 

 the expense of working up the collections. If this application 

 be granted, and the collections of the expedition of 1875 thus be- 

 come not a dead museum-material, but fructify for the purposes 

 of science, I hope that the sea visited by the expedition, for- 

 merly almost unknown, will soon be reckoned among those of 

 our globe which are well known in respect of their natural 

 history. 



Part of these scientific researches besides concern purely 

 practical questions, and I shall therefore, as they are concluded, 

 give you a short account of them. 



A. E. NORDENSKJoLD 



ON THE SPECTRUM OF NITROGEN AND 

 THAT OF ALKALINE METALS IN GEISS- 

 LER TUBES, BY M. SALET 



TN 1872 Mr. Schuster published the important statement that 

 " nitrogen, heated in a Geissler tube with metallic sodium, 

 ceased to give the characteristic channelled spectrum." He de- 

 scribed the bright lines he got in this case, and attributed them 

 to pure nitrogen, considering the band spectrum to be that of an 

 oxide of nitrogen, a compound destroyed by the alkaline metal. 

 These conclusions were afterwards disputed, for, in repetition of 

 the experiments, the channelled spectra were seen to disappear 

 after action of the sodium, but they were replaced by various 

 spectra, none of which belonged to nitrogen ; so that, after its 

 purification, this gas could not be detected by prismatic analysis. 

 The chemical compound really formed by the action of oxygen 

 on nitrogen is (as M. Salet pointed out) peroxide of nitrogen, a 

 very stable substance, whose spectrum does not coincide with 

 that, the appearance of which is to be explained. 



In a recent note to the French Academy, M. Salet affirms 

 (i) that the channelled spectrum may be produced with nitro- 

 gen heated in contact with sodium ; (2) that the disappearance 

 of the nitrogen spectrum is due to that of the nitrogen itself, 

 which is entirely absorbed by the sodium under the influence of 

 the electric discharge ; (3) that the spectrum described by Mr. 

 Schuster may probably be attributed to vapours of the alkaline 

 metal. 



He describes some of his more decisive experiments. A closed 

 tube of hard glass was procured, 12 cm. long and 2 cm. in diameter ; 

 at one end were introduced two aluminium electrodes, about 

 I era. apart ; to the other end was soldered a tubulure with an 

 enlarged part, into which was put a small piece of sodium, then 

 the tubulure soldered to the mercury pump, A vacuum having 

 been made, the sodium was heated ; it swelled and boiled, 

 parting with hydrogen ; the swelling at length ceased, and at a 

 higher temperature the sodium was slowly volatilised. Then the 

 apparatus was separated from the pump, with the blowpipe ; 

 and the bright liquid and globule of sodium was brought 

 into the tube. After cooling, the enlarged part was sepa- 

 rated, and the tube directly fused on to the pump. Then 

 exhaustion was recommenced, and the sodium volatilised, care 

 being taken that the condensation of the metallic vapour occurred 

 only in the half of the tube not holding the electrodes ; and nitro- 

 gen, pure and dry, was then admitted. A vacuum was produced 

 anew three times with the nitrogen, the alkaline metal being 

 volatilised each time. Lastly, the apparatus was closed, having 

 a pressure of about 5 mm. It was now possible to fuse the 

 globules, unite them, and volatilise them afresh a dozen times in 

 contact with the same mass of gas, without the appearance of 

 the spark between the electrodes being in the least degree modi- 

 fied. The Holtz machine was used, or an induction coil with a 

 Leyden jar ; the interpolar space was roseate violet, and gave 

 the channelled spectrum with the greatest distinctness. When 

 the disruptive spark of the Holtz machine is employed, the jet 

 of roseate violet light giving the channelled spectrum is instan- 

 taneous, as can be shown by a simple method (which M. Salet 

 described). By volatilisation the sodium may easily be brought 

 to the neighbourhood of the electrode. It there appears in the 

 form of brilliant globules of a very pure silver white ; but if the 

 tube be set in action, the portions subjected to the action of the 

 luminous discharge are at once tarnished. The metallic surface 

 quite disappears, and is replaced by a brownish black. At the 



same time one sees in the appearance of the electric jet changes 

 produced which are caused by a greater rarefaction. If the sur- 

 face of the sodium be renewed the action continues, and the 

 spectrum of nitrogen presently quite disappears ; the light is 

 yellowish, and due, for the most part, to sodium ; there are, in 

 general, slight impurities (from the electrodes and glass), which 

 give some strange lines. 



M. Salet made a direct experiment to show this absorption of 

 nitrogen by sodium under the influence of electricity. He made 

 a tube like the one that has been described, but bearing a trun- 

 cated barometer ; and introduced nitrogen at a pressure of 

 27 mm. The absorption of the gas was sufficient for one to be 

 able to follow with the eye the ascent of the mercurial column. 

 After a few minutes, having twice renewed the surface of the 

 sodium, no difference could be perceived between the mercury 

 surfaces in the two branches of the manometer. 



The author also sought to characterise this absorption chemi- 

 cally. He broke a tube and treated separately with water a por- 

 tion of the sodium remaining bright and a portion of the sodium 

 altered by electricity. Into the solution he poured Nessler's test. 

 One of the two liquids was strongly coloured yellow ; it was that 

 containing the altered sodium, the other was not altered in 

 aspect. There was formed, then, under the influence of elec- 

 tricity, nitride of sodium decomposable by water with production 

 of ammonia. This body is formed only at a temperature higher 

 than red, like nitride of magnesium ; or even is not produced 

 directly at any degree of heat, like ammonia. M. Salet proposes 

 to prepare and analyse it. 



NOTES 

 We hear with regret that the publications of the Geological 

 Survey of the Territories by Prof. Hay den are likely to be 

 stopped by the partisans of rigid economy in the U.S. House of 

 Representatives. If this step be carried out it will be a serious 

 loss to the scientific men of Europe, as well as of America, The 

 discoveries which have been made by the staif under Prof. 

 Hayden's direction are of the highest value, both from a scien- 

 tific and a commercial point of view, and the liberality vnth 

 which they have been circulated in Europe by the American 

 Government has earned the gratitude of all who care for the 

 advancement of knowledge. We trust that the rumour is untrue. 

 If it be true, we hope that a voice of remonstrance will go forth 

 from Europe. The possibility of a political change putting an 

 end to a great national work like that of Prof. Hayden illustrates 

 one of the worst flaws in the American Constitution, the can- 

 celling of all Government appointments at the election of a new 

 president. 



M. Leverrier was not present at the Anniversary Meeting 

 of the Astronomical Society to receive the medal which for a 

 second time has been awarded him for his valuable Planetary 

 Tables. Ill-health, caused by his recent; great labours, was, we 

 believe, the cause of his absence. 



The Annual Address of the President of the Geological 

 Society will be given at the Anniversary Meeting to-morrow. 



We are gratified by the statement contained in the Queen's 

 Speech, that the Government intend to introduce, in the course 

 of the session, measures relating to Primary Education and the 

 Universities. An important article on the subject appeared in 

 Monday's Daily Nrws, in which the defects of the present con^ 

 stitution of our Universities are forcibly pointed out. It is 

 also shown how important a bearing the composition of 

 the Commission would have in the character of its work, 

 and that it would be but a proper act of deference to the 

 valuable labours of the Science Commission if the new com- 

 missioners numbered some eminent representatives of science. 

 What the direction of the proposed University reforms is 

 likely to be may be to some extent gathered from the " in* 

 spired " hint dropped by the Dean of Christ Church, on Tuesday, 

 in connection with the proposal to retain the services of Prof. 

 Max Midler for Oxford, The Dean was authorised to state that 



