EFFECTS OF PRESSURE ON NITRATES. 



587 



TABLE II. 



Silver Nitrate. 



difPerence of compressibility. On the low pressure end of the curve 

 the high temperature phase is the less expansible, but at the other 

 end of the cui"ve it becomes more expansible. The change in sign of 

 Aj3 occurs at a lower pressure than that of Aa. Just what the struc- 

 tural change in the crystal is which brings about these changes in sign 

 of Aa and Aj8 is difficult to say; it may be a compacting together under 

 pressure of the crystal framework of the low temperature form which 

 makes it less responsive to changes of temperature and pressure. 

 The compressibility of AgNOs (II) would be expected to show con- 

 siderable variations with pressure just as ice I does. 



The difference of specific heat at atmospheric pressure, calculated 

 with the above values of Aa and Aj8, is 0.0082 cal. per gm., which 

 agrees almost exactly with the directly determined value, 0.008, of 

 Guinchant.^ The difference of specific heat decreases at the higher 

 pressures. There is no change of sign, however, but the high tempera- 

 ture phase has throughout the greater specific heat. 



Caesium Nitrate. This substance was most kindly loaned by 

 Professor Baxter, by whom it had been purified for his atomic weight 

 work. Immediately before using it was dried in vacuum at 100° for 

 several hours. This is a rare substance, and I was very fortunate to 

 be able to get enough of it to work with; I take this opportunity of 

 expressing my gratitude for Professor Baxter's kindness. 



