895 



How great llio ,iimi|) niiiLi,lil Ik\ was iincortaiii, owing lo tlie absence 

 of a batli which would keep liie (einperalure constant at wiiich tliis 

 cliange takes place. We wore therefore obliged to draw our conclnsions 

 from what we observed during a gradual heating, at which the 

 temperature can be only im[)erfectly estimated. A further investigation 

 was therefore necessary. Moreover, in repeating our determinations, 

 we encountered the difdcult}', that we found a different value for 

 the susceptibility of solid oxygen at the temperature of liquid hydiogen, 

 than in our lirst experiments, which were conducteil according to a 

 different method. Although we thought we were justified (Comm. N". 

 124) in considering that we had obtained reliable results only by 

 the second method, and that in the meantime we need not attach 

 any value to those obtained previously, it was still very desirable to 

 confirm tiie more recent value for the jump by new measurements. 

 Finally, in our experiments we came upon another problem that 

 recpiired to be solved. We had noticed (see Comm N". 122a May 

 1911) as Wahi/j also observed later, that solid oxygen, besides 

 appearing in the blue-grey opaque form that it usually presents, also 

 occurs in a transparent vitreous form. This modification can optically 

 be very clearly distinguished from the liquid state. We conjectured 

 that the transition from the transparent condition to the other one 

 might be accompanied by a second jump in the magnetic condition, 

 followirg on that which took place on freezing. We wished to 

 ascertain the truth of this also. 



§ 2. Armmienient of the e.vperiinents. For the magnetic determi- 

 nations, as in previous investigations, we made use of the method 

 of measuring the attraction which the magnetic field e.>:erls upon a 

 rod of the experimental substance placed at right angles to the field 

 in the interferrum of an electro-magnet, and held suspended there 

 by a carrier with hydrometer-arrangement. 



More specially the arrangen»ent of the apparatus was in the main 

 the same as that used for our investigations of the liquid mixtures 

 of oxygen and nitrogen, of which we shall give a complete description 

 in the next paper i^Comm. N". J39</). We do not give it here, 

 because the investigation treated in this paper, is of a much more 

 preliminary character than our investigation of mixtures, confining 

 ourselves here in the main to that wiiich is peculiar to our experiments 

 on solid oxygen. At the outset it should be mentioned that the way 

 in which the temporary connection was made between the carrier 



') Zeitschrift fur physikal. Chemie. Bd. 8-t (1913). 



