The Cybotactic Condition of Isopentane in the Region of the Critical Point

X-ray diffraction-ionization curves have been obtained, at various values of pressure, volume and temperature, of isopentane near the critical point. The results are: (1) that, as is the case with ethyl ether, the specific volume is unique in determining the extent of cybotactic groups; (2) that the specific volume at which these groups disappear is ninety percent greater than the critical volume; (3) that the internal description of liquefaction above the critical pressure, as the fluid passes from gas to liquid, is the same for both isopentane and ethyl ether.