438 Some Physical Properties of Nickel Carbonyl. [Mar. 3, 



but did so at 100° C, and, after heating for a few hours at this tem- 

 perature, no nickel carbonyl could be detected in the tube. After 

 standing for a few days, however, nickel was deposited when a clean 

 portion of the tube was heated with a pointed flame, thus sho wing- 

 that nickel carbonyl had been regenerated. In the 100 mm. tube 

 nickel was still deposited after heating for two days at 100° C. ; all 

 "the nickel carbonyl was found to have disappeared after the tube had 

 been heated for some time to 130° C. Nickel was deposited in the 

 tube at 226 mm. pressure at 130° C, in the 301 mm. tube at 158° C, 

 and in the other tubes at slightly higher temperatures. In the two 

 tubes at the highest pressures there was a considerable quantity of 

 the carbonyl present after heating for an hour at 160° C. All the 

 tubes in which the nickel carbonyl had been so far destroyed that no 

 visible deposit of nickel could be obtained on heating a clean portion 

 of the tube with a small flame, after standing for a few days 

 contained enough of the carbonyl to be readily detected by the 

 .above test. 



Another form of experiment suitable for demonstration proved 

 the reaction proceeded rapidly at the ordinary temperature, and 

 with a measurable velocity at low temperatures, even when the 

 pressure of the carbonic oxide atmosphere was below 200 mm. A 

 large bulb of about 200 c.c. capacity was connected to a mercury 

 manometer of small bore (so that the movements of the mercury in 

 the manometer were proportional to the changes of gas concentration 

 in the bulb). The bulb was highly exhausted and then filled with pure 

 .nickel carbonyl vapour to a pressure of 51 mm. of mercury at 15° C. 

 After heating for about an hour to 100° C. the pressure, measured after 

 cooling, had risen to 143 mm., corresponding to a decomposition of 

 about 60 per cent, of the nickel carbonyl present. Heated in a 

 glycerine bath to 154° C. the pressure reached 198 mm., corresponding 

 to practically complete decomposition, which ought to clevelope a total 

 pressure of 204 mm. 



On rapidly cooling the bulb and allowing it to stand at the ordinary 

 temperature the pressure fell, at first, about 3*2 mm. in an hour, then after 

 two days it had fallen to 120 mm., or about 55 per cent, had recom- 

 bined, after four more clays the pressure was 97 mm., or about 60 per 

 cent, had recombined, after standing four weeks some of the deposited 

 nickel remained unattacked. 



The bulb was again heated to 150° C, so as to deposit all the 

 nickel on the lower part of the tube, and the pressure now rose again io 

 200 mm. The lower part of the bulb where the nickel had deposited, 

 was now immersed in liquid air, when it was observed that still a 

 small but distinct diminution in pressure took place after some hours. 

 Liquid carbonic oxide did not, however, appear to react with nickel 

 reduced from the oxide by hydrogen. 



