72 BRIDGMAN. 



temperatures, and becomes inappreciable above 80°. In Figure 16 

 the point obtained at 75° with the restrained carbamide has been 

 included; this is legitimate if this point is regarded merely as setting 

 an upper limit. 



It has already been mentioned that carbamide was the substance 

 which shows a reaction velocity of a smaller order of magnitude at 

 points within the extrapolated region of indifference. This phenome- 

 non was observed at 0°. It was possible to detect motion at points 

 only 65 kgm. apart, whereas the extrapolated width of the indifferent 

 band was 435 kgm. 



AcETAMiDE. — The results are to be published in the following 

 paper. ^ Measurements of the rate were made only with a speci- 

 men which was afterwards found to be impure. The results are 

 too irregular for graphical representation. The acceleration with 

 falling pressure is throughout about twice as great as that with rising 

 pressure, and increases markedly with rising temperature along the 

 transition line. The width of the indifferent band falls greatly with 

 increasing temperature from about 700 kgm. at 25° to about 70 kgm. 

 at 100°. Above 100°, although no measurements were made on the 

 pure specimen the band of indifference remained of appreciable width, 

 perhaps of the order of 50 kgm. 



Potassium Chlorate. — A large number of measurements were 

 made on this substance, ^"^ but it does not pay to reproduce them in 

 detail because the effects were different in character than for other 

 substances. It has already been stated that at the lower temperature 

 the region of nucleus formation was so extensive as to cover the entire 

 region of observation, so that the pure surface growth could not be 

 observed. At higher temperatures, however, the phenomena become 

 like those for normal substances. The acceleration with falling pres- 

 sure is greater than with rising, and both accelerations become greater 

 at higher temperatures. There is a well defined band of indifference 

 which becomes narrower at the highest temperature. That there 

 should be a band of indifference at all shows that the effect of rising 

 temperature is much less in increasing the facility of nucleus formation 

 than in increasing surface transition velocity. 



10 E, p. 78. 



