1892.] on Metallic Carhonyls. 671 



important and interesting compounds called aromatic compounds, 

 including all the coal-tar colours, which have furnished us with an 

 undreamt of variety of innumerable hues and shades of colour, as 

 well as many new substances of great value to suffering humanity as 

 medicines. Surely a startling result, which alone would have fully 

 justified Liebig's prediction of 1834 ! 



Speaking of coal-tar colours, everybody will be reminded of the 

 great loss the scientific world has recently sustained by the death of 

 August Wilhelm Hofmann, their first discoverer, Liebig's greatest 

 pupil. Hofmann will ever be remembered in this Institution, where 

 he so often delighted the audience by his lucid lectures, and in whose 

 welfare he took the greatest interest, of which he gave us a fresh 

 proof only last year, in the charming letter he wrote on the occasion 

 of his election as an Honorary Member. 



Looking back upon the wonderful outcome of Liebig's idea I have 

 referred to, it seems surprising indeed that others should not have fol- 

 lowed up his work by attempting to obtain other metallic carbonyls. 



A very few experiments were made with other alkaline metals. 

 Sodium, otherwise resembling potassium so closely, has been shown 

 not to combine with carbonic oxide ; lithium and calcium are stated 

 to behave similar to potassium. But metals of other groups received 

 little or no attention. The very important role which carbonic 

 oxide plays in the manufacture of iron did lead to a number of 

 metallurgists (among whom Sir Lowthian Bell and Dr. Alder 

 Wright are the most prominent) to study its action upon metallic 

 iron and other heavy metals, including nickel and cobalt at high 

 temperatures. They proved that these metals have the proj)erty to 

 split up carbonic oxids into carbon and carbonic acid at a low red heat, 

 a result of great importance, which threw a new light upon the chemis- 

 try of the blast furnace. None of these investigators, however, turned 

 their attention to obtaining compounds of these metals with carbonic 

 oxide, and, owing to the high temperature and the other conditions 

 under which they worked, the existence of such compounds could not 

 come under their observation. In order to obtain these compounds, 

 very special conditions must be observed, which are fully described 

 in the papers I have published during the last two years in conjunc- 

 tion with Dr. Danger and Dr. Quincke* 



The metals must be prepared with great care, so as to obtain 

 them in an extremely fine state of division, and must be treated with 

 carbonic oxide at a low temperature. The best results are obtained 

 when the oxalate of the metal is heated in a current of hydrogen at 

 the lowest temperature at which its reduction to the metallic state is 

 possible. I have in the tube before me metallic nickel prepared in this 

 way, and over which a slow current of carbonic oxide is now passing. 

 The carbonic oxide before entering the tube burns, as you see, with 

 a blue non-luminous flame. After passing over the nickel it burns 

 with a highly luminous flame, which is due to the separation of me- 

 tallic nickel from the nickel carbonyl formed in the tube, which is 



