676 Mr. Ludwig Mond [June 3, 



The ferro-carbonyl is prepared in a similar manner to the nickel 

 compound. The iron used is obtained from the oxalate at the very- 

 lowest temperature possible, and is in a high degree pyrophoric. It 

 immediately catches fire on coming into contact with air, as I will 

 show you. 



This carbonyl forms, however, with such great difficulty, that we 

 overlooked its existence for a long time, and great precautions have to 

 be taken to obtain even a small quantity of it. It forms an amber- 

 coloured liquid, of which I have a small quantity before me. It 

 solidifies below — 21° C. to a mass of needle-shaped crystals. It distils 

 completely at 102^. Its specific gravity is 1*466 at 18^ C. On 

 heating the vapour to 180° it is completely decomposed into iron and 

 carbonic oxide. The iron mirrors before me have been obtained in 

 this way. Its chemical composition is Fe(C0)5. 



It is interesting that, within a short time after we had made known 

 the existence of this body, Sir Henry Roscoe found it in carbonic oxide 

 gas which had stood compressed in an iron cylinder for a considerable 

 time, and expressed the opinion that the red deposit which sometimes 

 forms in ordinary steatite gas-burners is due to the presence of this 

 substance in ordinary illuminating gas. Its presence in compressed 

 gas used for lime-lights has been noticed by Dr. Thorne, whose 

 attention was called to the fact that this gas sometimes will not 

 give a proper light because the incandescent lime becomes covered 

 with oxide of iron. 



M. Gamier, in a paper communicated to the French Academy of 

 Science, supposes even that this gas is sometimes formed in large 

 quantities in blast-furnaces when they are working too cold, and 

 refers to some instances in which he found large deposits of oxide 

 of iron in the tubes leading away the gas from these furnaces ; 

 but I find it difficult to believe that the temperature of a blast 

 furnace could ever be sufficiently reduced as to give rise to the 

 formation of this compound. On the other hand, it is highly pro- 

 bable that the formation of this compound of iron and carbonic 

 oxide may play an important role in that mysterious process by 

 which we are still making, and have been making for ages, the 

 finest qualities of steel, called the cementation process. 



The chemical behaviour of the substance towards acids and 

 oxidising agents is exactly the same as that of the nickel compound, 

 but to alkalies it behaves differently. The liquid dissolves without 

 evolution of gas. After a while a greenish j^recipitate is formed, 

 which contains chiefly hydrated-ferrous oxide, and the solution 

 becomes brown. On exposure to the air it takes up oxygen ; the 

 colour changes to a dark red, whilst hydrated-ferric oxide separates 

 out. 



We have so far not been able to obtain from this solution any 

 compound fit for analysis, and are still engaged upon unravelling 

 the nature of the reaction that takes place, and of the compounds 

 that arc formed. 



