ii8 



BRIDGMAN. 



No other modifications of the solid were found to 12000 at 25"^ 

 to 12500 at 200°. 



or 



Urethan. This was obtained from Eimer and Amend, and further 

 purified by crystalhzation at constant temperature in the thermostat. 

 Beautiful, colorless, transparent crystals were obtained, columnar in 

 form, some of them 2 or 3 inches long. The melting isothermals 

 showed very little rounding of the corners, so the purity must have 

 been fairly high. A remarkable property of the crystals is their 

 great flexibility; they may be bent in the fingers like paraffine. It is 

 possible that this may be due to twinning, as in the case of calcite; 



160' 

 140" 

 120" 



|p!|liSr|aruJffipfli]Mxl^^ 



wm 



3450789 10 11 12 

 Pressure, kgrn./cm.^ x 10* 

 Urethan 



Figure 31. Urethan. The observed equilibrium temperatures and pressures. 



it would be an interesting subject for investigation. Two fillings of 

 the apparatus were used. The first gave the low pressure point and 

 nine points at higher pressures. After this, the splitting of the steel 

 shell necessitated the using of another sample, with which twelve 

 points at high pressures were obtained, completing the phase diagram. 

 The quantities used were 17 and 13.5 gm. The urethan was melted 

 into the inverted nickel steel shell and pressure transmitted to it by 

 mercury. 



Two new solid modifications were found; these are so situated in 

 the phase diagram that all the triple points and equilibrium lines 



