NA TURE 



[December 8, 1892 



full vigour of youthful energy, and therefore he treated with 

 contempt a rumour that had reached him that the director was 

 in his eighty-fourth year. They would join with him in wishing 

 Prof. Pritchard a long continuance of the health and strength 

 which were turned to such splendid account. The second of 

 these medals was awarded to Dr. Langley, of the University of 

 Cambridge, for the long-continued and very valuable physiolo- 

 gical researches. There was a familiar phenomenon observable 

 before sitting down to dinner, and known as watering of the 

 mouth. If it were possible to determine the exact condition of 

 that operation in physiology the exact knowledge would be a 

 key to an immense range of the secrets of Nature. It was these 

 problems that Dr. Langley had been investigating, and he had 

 come nearer lo their solution than any one else. The Davy 

 medal was awarded to a distinguished French j-az/aw^, M. Raoult, 

 whose work was considered of the highest importance ; and he 

 rejoiced that the recipient of the medal was present. The Dar- 

 win medal was instituted in honour of one of his best and dearest 

 friends, and it was now conferred upon a man who was one of the 

 stanchest friends he had had for the last forty years. He might 

 fairly appeal to Sir Joseph Hooker's present activity, put him 

 down also among the young men, and thereby save the credit of 

 the council in the matter of its own regulation. To those who 

 knew the " Life and Letters of Darwin," talk about Sir Joseph 

 Hooker's right lo the Darwin medal was as futile as the attempt 

 to judge Manlius in sight of the Capitol. He knew no more 

 remarkable example of life-long devotion, of stores of informa- 

 tion laid open, of useful criticism, and of still more useful en- 

 couragement, by one man to another, than that exhibited by Sir 

 Joseph Hooker in this picture. It might be that even the man 

 whose motto was " It's dogged as does it," and who so pa- 

 tiently laboured for half a lifetime at the great fabric of the 

 origin of species, might have fainted by the way without this 

 friend's aid. And assuredly Hooker's great study of geogra- 

 phical distribution was a most important factor in Darwin's work. 

 It lay in the eternal fitness of things that Wallace and Hooker 

 should receive the Darwin medal ; and that these oid young-men 

 should give it a heightened value for the young young-men to 

 whom it would hereaiter pass. 



Prof. Raoult returned thanks, speaking in French. 

 Dr. Langley responded for the other medallists and himself. 

 Sir James Paget briefly proposed "The Guests." 

 The Swedish Minister, in responding, said — The honour to 

 be your guest and to participate with you in the celebration of 

 this interesting day cannot be more thankfully felt than by me, 

 who still has to consider this favour, above all, as a compliment 

 to the country where you have selected this year your Rumford 

 medallist. This distinction to my fellow-countryman. Prof. 

 Duner, v\hose meiits Prof. Huxley has so eloquently explained 

 to you, is a new link in the long chain of tokens of sympathy and 

 appreciation from this society to scientific Scandinavians, a 

 chain of which one of the oldest links is the creation of the Linnean 

 Society. More than a hundred years have passed since, and in the 

 meantime many systems have been altered ; and, especially in 

 the last twenty years, those alterations have so closely followed 

 the one upon the other that we laymen have been accustomed 

 to believe we were entitled to ask every new morning, " What 

 great discovery will this day bring ?" In one departcuent, how- 

 ever, scientific men as well as laymen cannot admil the possi- 

 bility of any alteration, and that is in our convjction and belief 

 that this country occupies a prominent place in the universal 

 scientific movement — a proof of which, among many others, is 

 the fact that no other institution in the world encourages as 

 much as does this society other countries' scientific researches. 



Mr. Alma-Tadema also responded, remarking in the course 

 of his speech that there v\ as no art without science, neither was 

 there any science without art : and that art coloured life as the 

 sun colours the flowers of nature. 



from the singular compound prepared somewhere about the year 

 1866 by the late Dr. Peter Griess, and which has hitherto been 



known as diazobenzene imide, CgHg — N 1| . This com- 



\n 



pound is now recognised as the phenyl ester of azoimide. It is, 

 however, a substance of very considerable stability, and success- 

 fully resists the attack of concentrated alcoholic potash, even 

 under pressure. Although thus stoutly resisting direct attack, 

 Drs. Noelting and Grandmougin have shown that by under- 

 mining its constitution by the introduction of a couple of nitro 

 groups in the place of two hydrogen atoms, it becomes weakened 

 so greatly as to be no longer capable of withstanding the action 

 of the alkali, and is decomposed with production of the 

 potassium salts of azoimide and dinitro-phenol — 



CeH3(NOo)2N3 + 2KOH = CgH3(NO.^)20K -f- N.,K + H^O. 



This interesting result is now supplemented by showing that it 

 is not necessary to introduce two nitro groups in order to render 

 diazobenzene imide sutificientiy negative in character as to be 

 susceptible to the attack of alcoholic potash, that one. such group 

 suffices, provided it be introduced in the para or ortho position. 

 A nitro group introduced in the meta position appears to exert 

 much less weakening power, quite inadequate for the purpose. 

 N = N 



AZOIMIDE. 



A FURTH ER communication concerning azoimide, the interest- 

 ing compound of hydrogen and nitrogen, N3H, discovered two 

 years ago by Prof. Cuitius, is contributed to the current number 

 of \\\tBerichte by Drs. Noelting and Grandmougin of Miilhausen, 

 in conjunction with Herr O. Michel. As described in our note 

 of vol. xliv. p. 600, Drs. Noelting and Grandmougin have pre- 

 viously shown that azoimide may be obtained by indirect means 



NO. 1206, VOL. 47] 



Para nitro diazobenzene imide. 



N 



NO, 



is a substance crystalliz- 



ing well in colourless tabular crystals. When these crystals are 

 allowed to fall slowly into a cold solution of one part of caustic 

 potash in ten parts of absolute alcohol, they instantly dissolve 

 and the liquid becomes coloured a deep red. If this red solution 

 is warmed for a couple of days over a water bath, and the larger 

 portion of the alcohol subsequently distilled off, upon acidifica- 

 tion of the residue with dilute sulphuric acid, and again dis- 

 tilling, azoimide, N3H, passes over along with the vapours of 

 water and alcohol. In order to free the azoimide from alcohol 

 it is only necessary to neutralize the distillate with soda, and 

 evaporate the solution to dryness, when the sodium salt of 

 azoimide, NjNa, is obtained ; the sodium salt is then dissolved 

 in water, the solution acidified with sulphuric acid, and sub- 

 jected to distillation, when an aqueous solution of azoimide is 

 obtained. The yield of azoimide is usually only about 40 per 

 cent, of the theoretical, owing to secondary reactions which 

 occur simultaneously with the main one. The ortho compound, 

 N = N 



NO., 



treated in a similar manner, also furnishes azoimide 



to the extent of about 30 per cent. A very much larger yield, 

 about 85 per cent., is afforded by the dibrom derivative of 



N=N 



\/ 



N 



the para compound, Br ( \ Br, a substance which is readily 



NO2 

 obtained in the form of long colourless prisms. Azoimide has 

 also been obtained to the extent "f 30 per cent, of the theoretical 

 amount by the decomposition of a nitro toluene derivative of 



N=N 



\/ 



N 



azoimide of the constitution 



CH3. 



NO, 



