looi 



iron is attended witli a, variation of volume, as in tiiis way an 

 important support nii^lit l)e given to (lie supposition of an internal 

 transformation. 



In a dilatometer constructed specially for the purpose FejOj was 

 reduced with hydrogen under such circumstances (temp, and time) 

 thai on the ground of experiments, previously taken, the iron could 

 certainly be assumed to be pyrophoric. Then the apparatus was 

 exhausted and filled with mercury, which had been boiled at the 

 airpump ^). 



In connection with the experiments in sealed to glass tubes it 

 was to be expected that in case of one or two days' heating nothing 

 could be observed until the neighbourhood of 300° is reached. In 

 agreement with this the following was found : 



Temperature 



Duration of 

 heating 



Change of position of 

 the mercury meniscus 



Accordingly it appeared most convincingly from the dilatometric 

 investigation that a considerable increase of volume lakes place 

 exactly in the temperature region where the pyrophoric property of 

 the iron vanishes with such rapidity that it can no longer be 

 demonstrated after ± 48 hours. In virtue of these preliminary 

 experiments it may, therefore, be considered as certain that the 

 transition of pyrophoric iron to ordinary iron is accompanied with 

 an increase of volume. The supposition that pyrophoric iron is iron 

 that is not in internal equilibrium, has thereby greatly gained in 

 probability. In a subsequent communication it will be demonstrated 

 why pyi'ophoric iron must not be considered as a new modification 

 of iron. 



Amsterdam, Febr. 27, 1914. Anon/. Chein. Lab. of tke 



University . 



^) Iron and mercury were examined after llio experiment v.-as over, when the 

 mercury appeared to contain only exceedingly small traces of iron, and the iron 

 to be perfectly free from mercury. 



-) At the end of the experiment the iron appeared to be no longer pyrophoric. 



