The Magnetic Susceptibilities of Several Organic Gases

Abstract

A method for measuring the magnetic susceptibilities of gases similar in principle to that used by Wills and Hector but simpler in operation was developed. The following results given in molecular susceptibility ×${10}^6$ were obtained: methane (C${\mathrm{H}}_4$), -12.2; ethane (${\mathrm{C}}_2$ ${\mathrm{H}}_6$), -27.3; propane (${\mathrm{C}}_3$ ${\mathrm{H}}_8$), -40.5; butane (${\mathrm{C}}_4$ ${\mathrm{H}}_{10}$), -57.4; isobutane (${\mathrm{C}}_4$ ${\mathrm{H}}_{10}$), -56.3; ethylene (${\mathrm{C}}_2$ ${\mathrm{H}}_4$), -12.0; acetylene (${\mathrm{C}}_2$ ${\mathrm{H}}_2$)-12.5; using as standards ${\mathrm{H}}_2$, -3.94 and ${\mathrm{N}}_2$, -11.8. These values are in error by less than 4 percent relative to each other. It is shown that the results cannot be reconciled with the assumption that the susceptibility of one of these molecules is equal to the sum of the susceptibilities of the atoms of which it is made up. The hypothesis is suggested that the susceptibilities of these substances are determined by the binding electrons, and it is shown that this assumption leads to a satisfactory interpretation of the observations if the two C${\mathrm{H}}_2$ groups of ethylene are supposed held together by electrostatic forces, and the two CH groups of acetylene by a bond similar to the ordinary C-C bond, such as in the ${\mathrm{C}}_{\mathrm{n}}$ ${\mathrm{H}}_{2\mathrm{n}+2}$ molecules. It is shown that among the previous measurements of the susceptibility of ${\mathrm{H}}_2$ and ${\mathrm{N}}_2$ those made by Wills and Hector are probably the most nearly correct.