66 BRIDGMAN. 



it is certain, however, that the reaction with falHng pressure is the 

 more rapid, and that in general the reaction becomes slower at the 

 higher pressures. This seems natural w^hen we recall that this tran- 

 sition is of the ice type, higher pressures corresponding to lower 

 temperatures. The band of indifference is very narrow, too narrow 

 to accurately measure. It seems, however, to increase regularly in 

 width with increasing pressure, from about 15 kgm. at a pressure of 

 6S0 kgm. to 40 kgm. wide at 3080 kgm. 



Carbon Tetrabromide.* — Observations at only two temperatures 

 were made, on the II-III curve. At 176.6° the accelerations from 

 above and below were 0.00076 and 0.00038 parts per minute per kgm. 

 respectively, and at 152°, 0.00052 and 0.00069. The reversal in 

 order of magnitude is probably not genuine; because of decomposi- 

 tion these results can at best give only the order of magnitude. The 

 band of indifference was 50 and 90 kgm. wide at the two temperatures 

 respectively; as is normal, the width is greater at the lower tempera- 

 ture and lower pressure. 



Urethan.^ — ^Measurements were made at only one point, at 0° 

 for the transition I-III. The accelerations were 0.000088 from above 

 and 0.000060 from below, rather slower than the usual. In the pre- 

 ceding paper mention has already been made of the curious behavior 

 of the band of indifference, that it is wider on the I-II and III-II 

 curves at temperatures above the triple point than it is on the I-III 

 curve below the triple point. 



Camphor. — The transition data of this substance has not yet been 

 published^; it is fairly complicated and contains six modifications. 

 The only one of the transitions with a change of volume large enough 

 so that the time rate could be measured is II-III. The transition line 

 runs from approximately 23° and 2800 kgm. to 115° and 11900 kgm. 

 with little curvature. The accelerations on this curve are showTi in 

 Figure 9. The reaction is more rapid with falling than with rising 

 pressure (the reversal at 6000 is probably not genuine) and grows more 

 rapid at the higher pressures. The breadth of the band of indifference 

 is shown in Figure 10; the band becomes rapidly wider as the pressure 

 increases. It is remarkable that the reaction velocity should increase 

 at the same time that the limits of indifference become wider. 



Caesium Nitrate. '^ — There are two modifications, the transition 



4 E, p. 90. 



5 E, p. 118. 



6 See, however, F for the general nature of the phase diagram. 



7 G, p. 587. 



