EFFECTS OF PRESSURE ON NITRATES. 013 



temperature form are of great interest. Wallerant was able to find 

 that its crystalline system was the same as that of II, and he suggested 

 that it was in fact the same modification. This appearance of the 

 same phase in two isolated parts of the phase diagram is unique, if it 

 should be proved, but seems to be not contrary to any of the thermo- 

 dynamic necessities. Behn has subjected the question to a very 

 careful experimental examination, measuring the various thermal and 

 crystallographical properties of II and V to see whether it is possible 

 to state an indentity. His data did not allow of a definite answer to 

 the question, but seem to suggest that II and V are not the same 

 phase. I did not make any measurements on this transition for the 

 reasons already stated, but did investigate one questionable point. 

 One might expect, since the transition IV-V is of the ice type, that at 

 higher pressures another phase would exist, so that the falling transi- 

 tion curve between IV and V would be replaced by a rising curve 

 between IV and the new modification. I did not find any such new 

 modification out to 12500 kgm. at room temperature. 



The following transition temperatures are found in the literature. 

 For I-II Lelimann ^^ gives 127°, Bellati and Romanese ^* give the 

 limits 124° to 125°, Lussana ^^ found the limits 124.9° and 125.6°, and 

 Schwarz ^ has found the value 125.6° by one method, and the limits 

 123.5° to 125.5° by another. In the table I have given 125.5° as 

 agreeing best with my own data and the best results of other observ- 

 ers. For the transition II-III Lehmann ^^ gives 87°, Behn ^^ gives 

 83°, Bellati and Romanese ^* give the limits 82.5° to 86°, Schwarz ^ 

 gives the limits 82.5° to 86.5° by one method, 82.8° to 82.7° by another, 

 and 83° by a third, Wallerant ^ gives 82°, Tammann ^^ gives by 

 extrapolation from his measurements at higher pressures the value 

 84.6°, and Lussana ^^ finds that the transition takes place at 85.85° 

 on heating, but does not give the value on cooling. I have adopted 

 the value 82.7° as agreeing best with my own data and those of 

 others. For the transition III-IV Lehmann ^^ gives 36°, Bellati and 

 Romanese^* give the limits 31° to 35°, Schwarz^ gives the limits 31° 

 to 35° by one method, 32.4° (best) by another, and 35° by a third, 

 Wallerant ^ gives 32°, Behn ^^ 32°, Tammann ^^ finds by extrapola- 

 tion from his high pressure measurements 31.8°, and Lussana ^^ finds 

 the limits 35.45° and 30.55° on heating and cooling. I have adopted 



U M. Bellati and R. Romanese, R. 1st. Ven. 4, 1395-1420 (1885-86). 



15 S. Lusgana, Nuov. Cim. (4), 1, 97-108 (1895). 



16 G. Tammann, Kristallisieren unci Schmelzen, Barth, Leipzig (1903), 

 p. 299. 



