104 



BKIDGMAN. 



indications are that the difference of specific heat between I and II 



changes sign along the transition line; at atmospheric pressure I has 



the smaller specific heat, but at the triple point that of II is the smaller. 



It must be insisted, however, that all these values are exceedinglv 



, dAV , clAH 

 rough ; 



and 



are not given at all accuratelv bv the above 



dp dp 



data. 



No other modifications were found to 12000 kgm. at either 20° or 

 200°. 



The form of I is cubic and that of II hexagonal, but the two forms 

 are very little different. 



Mercuric Iodide. This substance is the only one found so far 

 which shows a maximum transition temperature between two solids, 

 a result both unexpected and important. A great deal of time was 

 spent on this substance in order to exhaust every other possible ex- 



23456789 

 Pressure, kgm. /cm. ^ x lO"* 

 Mercuric Iodide 



10 U 



Figure 24. Mercuric Iodide. The observed equilibrium temperatures and 

 pressures. It was not possible for this substance to shut the equilibrium 

 conditions within narrow limits, and in the figure the limits of the reaction 

 are shown. The text should be consulted for further particulars. 



planation of the effects, and to establish this result beyond doubt. 

 It is particularly difficult to get accurate results for this substance, 

 because of the unusually wide region of indifference. The interpreta- 

 tion of the earlier results was also obscured liy occasional leaks through 

 a minute flaw in the cylinder; this flaw was due to amalgamation 



