604 KEPORT — 1891 



formula Ni (C0)[, viz., 34'33 aud 34:-26 percent, of nickel, the formula requiring 

 34'2S. The vapour density determined hj' Victor Meyer's method at 50° was found 

 equal to 6'01 ; the formula Ni (CO)^ requires 5-S9. 



The compound is chemically very inactive ; generally speaking, it only reacts 

 with substances having a considerable affinity for nickel, such as the halogens, sul- 

 phur, oxygen, and oxidising substances, which combine with the nickel and liber- 

 ate carbonic oxide. Chlorine and bromine when used in excess also enter into 

 combination with the carbonic oxide. Sulphur in the dry state forms a sulphide 

 of nickel corresponding to the formula Ni.iSj, and dissolved in bi-sulphide of carbon 

 it forms a sulphide containing more sulphur, but of varying composition. Selenium 

 acts similarly but very slowly. Tellurium shows hardly anj' action. Metals (even 

 potassium) are not acted upon. 



Alkalies and acids (even strong hydrochloric acid) produce no change except 

 they are oxidising agents, such as nitric acid and aqua regia. With metallic salts 

 no reaction is obtained unless they have oxidising properties as hypochlorites, 

 which form a higher oxide of nickel, or which are capable of giving oiF sulphur, such 

 as hyposulphites and bisulphites. 



The author has tried in vain to substitute other bivalent groups for the carbonic 

 oxide in this compound, or to introduce the carbonic oxide by means of this 

 compound into organic substances. Experiments in this direction have covered a 

 very wide range and have included, amongst others, the following : hydroxylamine 

 hydrochloride, phenylhydrazin hydrochloride hydroxylamine, dichloracetic acid, 

 tetrabromphenolbromiJe, ethylinechloride, and aceto-acetic-ether, but in no single 

 instance was the desired result obtained. 



On exposure to moist or dry air a tlocculent substance, which varies in colour 

 from a light green to a dark brown, is very slowly formed. This substance dis- 

 solves completely in dilute acids with evolution of carbonic acid ; numerous 

 analyses have not led to a definite proportion between Ni and CO., in this com- 

 pound. On heating it to dull red heat it turns black. Professor Berthelot, in a 

 paper recently communicated to the French Academy of Sciences, assumes that 

 this black colour is produced by the separation of carbon, and bases upon this an 

 argument that the compound is of a complex composition, and that the nickel car- 

 bon oxide, on exposure to air, behaves like a real compound radical analogous to 

 organo-metallic radicals. As, however, the black substance so obtained dissolves 

 in dilute acids without leaving any residue, aud as an exactly similar black sub- 

 stance is obtained by heating precipitated nickel carbonate, this argument does not 

 seem to be conclusive, since Professor Berthelot has not substantiated so important 

 a conclusion by a complete analysis of the black substance. 



Professor Berthelot describes in the same paper a very beautiful blue compound 

 obtained by treating nickel carbon oxide with nitric oxide. Unfortunately he does 

 not publish an analysis of this beautiful substance either, so that until he has done 

 so we are unable to judge of its bearing on the constitution of nickel carbon oxide. 

 AVith a view to elucidate this con.stitution the author has, in conjunction with 

 Professor R. Nasini, of Eome, studied the physical properties of the liquid, more 

 especially its refraction and dispersion. The details of this investigation have been 

 communicated to the Accademia dei Lincei at Rome, and have also been published 

 in the ' Journal fiir phj'sikalische Chemie.' 



The author has determined the freezing-point of a dilute solution in benzole 

 containing 4'8991 per cent., and has found the coefficient of diminution '2776, 

 corresponding to a molecular weight of 176'5 ; while nickel carbon oxide requires 

 170-6. The mean cubical coefficient of expansion between 0° and 3G° C. is equal to 

 •001853, which is one of the highest coefficients of expansion yet found for any 

 liquid, and is only slightly exceeded by ethylic ether, ethyl chloride, and silicium 

 tetrachloride. The indices of refraction and the dispersion for the lines a, (3, and y 

 of hydrogen, and for the lines of lithium, sodium, and thallium have been deter- 

 mined at three different temperatures, and are found to be very high. The dis- 

 persion is about the same as carbon disulphide. The refraction varies very much 

 with the temperature, the amount of variation being very nearly equal to that of 

 carbon disulphide. The index of refraction for the D line at 10° C. is 1-45843. 



