Effects of Pressure on Proton Spin-Lattice Relaxation in Several Degassed Organic Liquids

Abstract

The hydrogen nuclear magnetic relaxation time (T₁) for degassed samples of several organic liquids has been measured, by a transient method, at pressures up to 1400 kg/cm², primarily for comparison with results obtained without degassing. Certain of the liquids were investigated, without degassing, by Benedek and Purcell, who concluded that T₁ decreases under pressure less rapidly than the rates of translational processes (fluidity and diffusion). The present results confirm this for degassed methyl iodide and n‐heptane, in both of which the effect of degassing is to increase T₁ less than 20%. For benzene and toluene, degassing causes T₁ to increase by several hundred percent, and the preceding conclusion ceases to apply, but instead, in the degassed samples, the relative rate of decrease of T₁ under pressure is comparable to that of the fluidity; in benzene, at low pressures, it is greater. Additional pressure studies are reported for purified cyclohexane, for purified 1,1,1‐trichloroethane, and for chloroform, which was not successfully purified.