602 



BRIDGMAN. 



The interesting features of the diagram, apart from the two new 

 modifications, are the pronounced curvature of the II-III hne, and 

 the great proximity of the I-II-III triple point to atmospheric pres- 

 sure. It suggests itself that it might be possible under the proper 

 conditions to realize III at atmospheric pressure as an unstable form, 

 and as a matter of fact Wallerant has found an unstable form on 



23456789 

 Pressure, kgm./cm.^ x 10^ 

 Potassium Nitrate 



Figure 12. Potassium Nitrate. The computed heats of transition and 

 the changes of internal energy. 



cooling I l)elow the triple point to al)out 114°. This unstable form is 

 uniaxial, but Wallerant was not able to further characterize its crystal- 

 lographical system. 



There are a large number of determinations at atmospheric pressure. 

 For the transition temperature Bellati and Romanese ^° give the 

 limits 128.7° and 121.7° on heating and cooling, Bellati and Lussana ^^ 

 give 127.76°, Schwarz ^ gives the limits 121.5° to 129.5° by a thermal 



10 M. Bellati and R. Romanese, R. 1st. Ven. 3, 653-669 (1884-85). 



11 M. Bellati and S. Lussana, R. 1st. Ven. 2, 995-1023 (1890-91). 



