TRANSACTIONS OF SECTION B. 605 



According to Gladstone's formula this leads to the specific refraction of "3437 

 and the molecular refraction of 58'63. Under the supposition that the group CO 

 had the same value in this compound which results from the sum of the atomic re- 

 fraction of carhon and that of the divalent oxygen molecule in organic compounds, 

 which is the more probable, as the group GO shows ver}^ nearly the same molecular 

 refraction in compounds of the most different constitution, such as oxalic acid, 

 ketones, and carbonyldichloride, the atomic refraction of nickel would come out 

 equal to 2502. This figure is very much higher, nearly two and a half times as 

 high as it is in nickel salts, in which it has been found by Gladstone to be about 

 10 ; and about four times as high as the atomic refraction of metallic nickel as 

 determined by Kundt and Dubois and Rubens, viz., about 6. 



This difference of the atomic refraction of nickel in this compound and in its 

 ordinary combinations is by far greater than that found in any other element. 

 According to the generally accepted view, such differences are due to the element 

 possessing a large number of valencies, and are proportional to the number of 

 valencies of each compound. Nickel is generally bivalent. Its very high atomic re- 

 fraction in nickel carbon oxide would thus lead to the conclusion that in this 

 compound the nickel exercises a considerably higher valency than two, and that 

 it has probably reached its maximum of saturation foreseen by Mendeleeff, who 

 placed this metal in the eighth group of his Periodic System, to be equal to 

 eight ; so that the constitution of our compound would be a simple combination of 

 one oetovalent equivalent of nickel with four bivalent equivalents of carbonic oxide, 

 or that of nickel tetracarbonyl. 



All that we definitely know of the chemical properties of the compound is in 

 accord with this view of its constitution. 



A determination of the magnetic rotary power of the compound kindly made 

 by Dr. W, H. Perkin has shown this to be quite as exceptional as its refraction, 

 and, with the exception of phosphorus, greater than any substance he has yet 

 examined. 



Professor Quincke, of Heidelberg, has had the kindness to investigate the 

 magnetic properties of the liquid, lie found the constant of diamsignetism, at 

 1G° G., /fc= -3-131 X lO-io for magnetic fields of 6,000 to 14,000 G.G.S. units. 

 This is nearly the same as the constant for ethylic ether = — 3'218 x 10~'°. 



The liquid is an exceptionally bad conductor of electricity. Up to 40 volts no 

 current was observed to pass, the electrodes of 1 sq. cm. area being 1 cm. apart. 



The highly interestiug properties of nickel carbon oxide naturally led the 

 author to try whether he could not obtain similar compounds of other metals. 

 It seemed a foregone conclusion that cobalt, in every respect so much like nickel, 

 must give an analogous compound. It seemed probable that oth-^r metals of the 

 eighth group and those standing near to nickel in other groups would also 

 combine with carbonic oxide. A large number of elements were tried, including 

 osmium, palladium, ruthenium, rhodium, iridium, and manganese by acting upon 

 them in the finely divided state with carbonic oxide gas over a wide range of 

 temperature. The author tried it by double decomposition with numerous com- 

 pounds, including zinc ethyl and mercury methyl, but, with one sole and single 

 exception, without success. 



This sole exception is iron. This metal, too, had for a long time given 

 negative results ; but by preparing it at the lowest possible temperature by 

 reduction of the oxalate in a current of hydrogen, and by acting upon this at 

 about 80° G. with a very slow current of very pure carbonic oxide, the author 

 succeeded at last, in conjunction with Dr. F. Quincke, in obtaining evidence that a 

 volatile compound of this element with carbonic oxide exists. The gas obtained 

 imparted a yellow tinge to a Bunsen flame and yielded slight metallic mirrors 

 composed of pure iron. The quantity of the iron compound in the gas was, 

 however, extremely small. By passing the gas through heavy tar oils, in which 

 the compound is soluble, but from which it cannot be separated by fractionation, 

 as on heating it decomposes the solution into iron and carbonic oxide before it 

 volatilises, and by determining the iron and carbonic oxide so obtained, it was 

 ascertained, as far as the very small quantities of the substance available would 



