( 164 ) 



hour to 900° in an atmosphere of pure nitrogen by means of an 

 electrical furnace, on which it appeared that under these circum- 

 stances nothing was to be detected of a conversion of diamond into 

 graphite. 



When this favourable result had been obtained, a china dish filled 

 with diamond powder was placed in a china tube which was slowly 

 heated in an electrical furnace, a current of pure CO s passing through 

 the china tube. 



The escaping gas was led through a very sensitive solution of 

 PdCl t , so that the presence of CO in it was at once to be detected. 



The experiment showed that under these circumstances the reduc- 

 tion of CO, by diamond begins to be noticeable only at about 750°, 

 and proceeds rapidly at 850°. 



So after the conversion 



CO, + C^2CO 



had been shown in this way, we had to ascertain whether the reverse 

 reaction 



2CO^>CO, + C 



had taken place in the course of this process. 



For this purpose the CO, stream was suddenly broken while the 

 temperature was still increasing, and the gas-mixture in the china 

 tube was expelled rapidly and completely by means of pure nitrogen. 

 Only then the temperature was lowered, and the furnace cooled 

 down to the temperature of the room. 



The contents of the boat showed in an unmistakable way that the 

 latter reaction had really taken place, for the colour had become 

 grayish, in consequence of the depositing of graphite, which had 

 taken place throughout the mass. 



On repetition of the experiment the same result was obtained, so 

 that we think that we have given in this way for the first time a 

 direct proof of the correctness of the dynamic conception of a reversible 

 reaction. 



. 7 , Af\f\a Anorq. chem. Laboratorium 



Amsterdam, June 1908. ^ ^ University 



