428 



Prof. J. Dewar and Mr. K 0. Jones. 



[Mar. 3„ 



nickel carbonyl vapour was decomposed. The reaction 2C0 = C0 2 + C 

 liberates 38*8 kilogramme calories, so that if the heat of formation 

 of nickel carbonyl is less than 77*6 kilogramme calories per molecule, 

 this explanation would be valid. This condition is satisfied since- 

 Mittasch* has shown that the heat of formation of nickel • carbonyl 

 is between 50*6 and 55 -6 cals. Hence the detonation observed 

 by Mond might result from the reaction : 



Ni(GO) 4 = Ni + 2C0 2 +JC. 



The fact that nickel carbonyl was thus reported to be explosive,, 

 together with the explanation of its explosibility offered by Berth elot,. 

 strengthened the belief in its great instability and deterred experi- 

 menters from working with it, in any case at temperatures above its. 

 boiling point. 



The authors observed that when nickel carbonyl was suddenly 

 heated in an atmosphere of some inert gas, such as hydrogen or 

 nitrogen, the vapour decomposed quietly with deposition of metallic 

 nickel ; there was no explosion or flash of light, and the quantity of 

 carbon dioxide produced was so small, in most cases, as to be almost 

 negligible. This was found to be the case even when the temperature 

 used was as high as 130° C. Mittasch* states that he could 

 detect no carbon dioxide when the compound decomposed below 

 100° C. 



The explosion " observed by Moncl, Langer, and Quincke must 

 therefore have been due to the presence of oxygen, and does not 

 occur in its absence. The amount of carbon dioxide produced by the 

 quiet decomposition is very small, so that the Berthelot reaction,, 

 though possible, only takes place to a very slight extent. 



It was therefore clear that vapour-density determinations of the 

 compound could be made in atmospheres of inert gases at temperatures 

 much higher than 50° C. As vapour-density determinations of such a 

 unique compound as nickel carbonyl under varying conditions would 

 have a special interest and might well be expected to repay careful 

 study, a large number of vapour-density determinations were made 

 by Victor Meyer's method at temperatures between 63° C. and the 

 boiling point of naphthalene (216° C), in order to ascertain the effect 

 of increasing temperature on the dissociation of the compound. The 

 vapour-density apparatus was filled in different experiments with 

 various dry inert gases, viz., hydrogen, nitrogen and ethylene, all care- 

 fully purified and especially freed from oxygen. 



In order to trace the effect of the rapidity of gaseous admixture 

 on the dissociation various forms of the vapour-density reservoir were 

 employed. An atmosphere of carbon monoxide was employed to 



* Loc ext. 



