568 BRIDGMAN. 



Only one sample of the substance was used, 75 gm. in amount, and 

 both the high and low pressure determinations were made with it. 

 It was hammered dry into an open steel shell, and pressure was trans- 

 mitted directly to it by kerosene. Two determinations were made at 

 low pressures; one by ^•arying temperature at constant pressure to 

 give Av, and one by varying pressure at constant temperature to give 

 the transition point. Four points at higher pressures, all by the 

 isothermal method, ere sufficient. 



The domain of indifference is nowhere wide, but it varies greatly at 

 (liferent temperatures, a rather unusual effect. i\.t 100 kgm. it was 

 possible to shut the equilibrium pressure within limits only 11 kgm. 

 apart; at 177° the limits were 8 kgm., at 164° 17 kgm., and 189° 

 70 kgm., and at 202°, 125 kgm. It is unusual that the limits at 177° 

 were narrower than at 164°, but it is to be noticed that the 177° point 

 was determined fh-st; possibly the transition may have developed 

 fissures in the solid which would account for the wider limits at 164°. 

 It might be thought natural that along with the narrowness of the 

 bund of indifference at the lower temperatures would go a high rate of 

 reaction, but this was not so. The reaction velocity was distinctly 

 slower than for most solids; at 100 kgm. about 90 minutes were 



TABLE III. 



Caesium Nitrate. 



