POLYMORPHIC TRANSFORMATIONS OF SOLIDS. ^\f 



only 130°. Both his transition lines are straight. His II-III transi- 

 tion point at atmospheric pressure is 41.8° and his II-III line lies at 

 pressures from 30 to 50 kgm. higher than mine. The agreement in 

 both these cases is better than is usual between his results and mine. 

 On the I-II line, his atmospheric transition point is at 67.3°, and at 

 130°, his transition line is about 30 kgm. higher than mine. There 

 are apparently no other determinations of AV or the latent heat at 

 atmospheric pressure, and Tammann gives no values at high pressures. 

 Four measurements of the difference of compressibility between II 

 and III were made. There can be no doubt that III is less compressi- 

 ble, but there may be considerable question as to the numerical value 

 of the difference. On account of the decomposition between I and II, 



TABLE VIII. 

 Carbon Trichloride. 

 Differences between II and III. 



no good values for the difference of compressibility between these 

 forms could be obtained. The values of Aj3 and ACp computed from 

 the experimental values of Aa are shown in Table VIII. The numeri- 

 cal accm'acy is probably great enough so that one may say without 

 question that II is more expansible; it is however, questionable 

 whether the difference of expansion increases with rising pressure as the 

 table shows. On the average, the specific heat of II is also greater 

 than that of III ; one may well doubt whether the difference is negative 

 at atmospheric pressure as the table would show. 



The crystalline forms of the several modifications has been deter- 

 mined by Lehmann.^ The high temperature form is regular, the 



9 O. Lehmann, ZS. Krj^st. 6, 580-589 (1882). 



