1892.] 071 Metallic Carhonyls. 673 



nate of nickel is slowly formed of varying composition, which is 

 yellowish- white if perfectly dry air is used, and varies from a light 

 green to a brownish colour if more or less moisture is present. 



We have found all these precipitates to dissolve easily and com- 

 pletely in dilute acid, with evolution of carbonic acid, leaving ordinary 

 nickel salts behind, and can therefore not agree with the view pro- 

 pounded by Professor Berthelot in a communication to the French 

 Academy of Science, that these precipitates contain a compound of 

 nickel with carbon and oxygen, comparable to the so-called oxides of 

 organo-metallic compounds. In the same paper Professor Berthelot 

 has describod a beautiful reaction of nickel carbonyl with nitric oxide, 

 which Dr. Langer will now show you. You will notice the intense 

 blue coloration which the liquid solution of nickel carbonyl in 

 alcohol assumes by passing the nitric oxide through it. Professor 

 Berthelot has reserved to himself the study of this body, but has so 

 far not published anything further about it. 



The chemical properties of the compound I have just described to 

 you are without parallel ; we do not know a single substance of 

 similar properties. It became, therefore, of special interest to study 

 the physical properties of the compound. 



Professor Quincke, of Heidelberg, has kindly determined its 

 magnetic properties, and found that it possesses in a high degree the 

 property discovered by Faraday, and called by him dia-magnetism, 

 which is the more remarkable, as all the other nickel compounds are 

 para-magnetic. He also found that it is an almost perfect non-con- 

 ductor of electricity, in this respect differing from all other nickel 

 compounds. 



The absorption spectrum, and also the flame spectrum of our com- 

 pound are at present under investigation by those indefatigable spec- 

 troscopists, Professors Dewar and Liveing, by whose kindness I a,m 

 enabled to bring before you, in advance of a paper they are sending 

 to the Eoyal Society, some of the interesting results they have ob- 

 tained. We have here a photograph of the absorption spectrum, 

 obtained by means of a hollow prism through quartz plates filled 

 with nickel carbonyl, through which the spark spectrum of iron is 

 passed, which is photographed on the same plate. You see that the 

 whole of the ultra-violet rays of the iron spectrum have disappeared, 

 being completely absorbed by the nickel carbonyl, which is thus 

 quite opaque for all the rays beyond the wave-lengths 3820. 



The spectrum of the highly luminous flame of nickel carbonyl, 

 which I have shown you before, is quite continuous ; but if the nickel 

 carbonyl is diluted with hydrogen, and the mixture burnt by means of 

 oxygen, the gases burn with a bright yellowish-green flame without 

 visible smoke ; and the spectrum of this flame shows in its visible 

 part, on a background of a continuous spectrum, a large number 

 of bands, brightest in the green, but extending on the red side beyond 

 the red line of lithium, and on the violet side well into the blue. 

 These bands cannot be seen on the photograph which I will now 



