148 DR. W. WAHL: PHYSICO-CHEMICAL DETERMINATIONS AT HIGH PRESSURES. 
are those which, according to the formula of Lindemann, determine the “molecular 
frequency ” of the atoms. It seems therefore probable that the relation between the 
“ molecular frequency ” of the two crystalline forms determines the entire relationship 
between the pliysical constants of one form as compared with those of the other. 
As a general result of the intersection of the melting-point curves at the absolute 
zero, we thus find that the physical properties of the two modifications—which 
apparently behave like two distinct crystalline substances—would, when the absolute 
temperature is lowered, change gradually, and in a similar way, and become identical 
at the trij^le-point, the absolute zero, which thus also would represent a “ critical- 
point ” between these two modifications of the a^-bibrompropionic acid. 
2 k 
