82 



BRIDGMAN. 



runs were made with the pressure transmitted directly by kerosene, 

 while for the third run, the compacted mass was submerged under 

 mei'cury, by which the pressure was transmitted to it.^ Probably 

 none of the attempts to remove the moisture was entirely successful; 

 the KNO2 was always different in texture from any of the other sub- 

 stances. When hammered, it compacted into a coherent semitrans- 

 lucent mass, in texture like celluloid when cut with a knife. ^ 



The pressure limits within which the equilibrium was shut varied 

 from 40 to 360 kgm.; in general the limits were wider at the lower 

 temperatures, but the variations were very irregular. The irregularity 

 is partly mixed up with the varying quantity of impurity at different 

 stages of the reaction. The AT isothermal curves showed the effect 

 of impurity by being rounded at the corners. The rounding took place 



9 80 



5 6 7 8 9 10 



Pressure, kgm./cm.^ x 10^ 



Potassium Nitrite 



Figure 13. Potassium Nitrite. The observed equilibrium pressures^and 

 temperatures and the changes of volume. 



at both corners; this is very unusual, and is the only case of it that I 

 have found. It means that both of the phases form mixed crystals 

 with the impurities, and that the impurity which is miscible with one 

 phase is different from that miscible with the other. As one would 

 expect from the rounding of both corners, no lag of the reaction was 

 noticed in either direction from the transition line, at least beyond the 

 region of indifference. 



Beside the unusual rounding of both corners of the isothermals, 

 KNO2 is unique in that the reaction velocity is greater with rising 



