RICHARDS. — SIGNIFICANCE OF CHANGING ATOMIC VOLUME. 601 



In seeking for quantitative verification of such an effect, the irregu- 

 larities themselves are the best guide to their cause, hence the alcohols, 

 already quoted as abnormal in their behavior, serve as useful examples. 

 Fortunately, too, the heats of formation of enough alcohols are known, 

 in order to provide a clue as to a change of the interual stress within 

 the molecule. Below is given a brief table typically illustrating the 

 point. 



The Effect of Internal Atomic Rearrangement on Density. 



In the case of the propyl alcohols given in this table, the usual relation 

 exists, — the density is greater where the boiling point is greater, — 

 but in the case of the aniyl alcohols, on the other hand, an anomaly 

 appears. In the latter case the densities of the two compounds given in 

 the table are identical, although their boiling points are 29° apart. 



The most plausible explanation of this circumstance lies in the as- 

 sumption of increased internal atomic compression, due to the peculiar 

 structure of dimethyl ethyl carbinol ; a compression which has nothing 

 directly to do with the cohesive attraction and the boiling point, because 

 these are concerned only with the superficial attraction of the molecules. 

 By causing decrease in volume this internal stress serves to conceal the 

 increase in volume due to a lesser pressure of cohesion in the lower- 

 boiliug liquid. This hypothetical inference is supported by the heats 



* These figures are due to Louguinine (Am. chim. phys., (5) 21. 139(1880)). 

 Thomsen e figures show similar differences, although in a mure exaggerated degree. 

 Qualitatively they would lead to the same conclusion. 



