Pressure-Volume-Temperature Relations in Liquid and Solid Tritium

PVT relations in liquid and solid T₂ near the melting curve were measured over 20.5 K-22.1 K and 0 MPa-7 MPa (0 bar-70 bar) with a cell that used diaphragms for pressure and volume variation and measurement. Because of ortho-para self conversion, the melting pressure P and the liquid molar volume V_lm increased with time. The rates were consistent with a second order reaction similar to that for c the J = odd concentration: [Formula: see text]where k₁ = 6-9×l0^-2h^-1. By extrapolation, the ortho and para forms differed by ΔP ~6 bar and ΔV ~0.5%. Measurements of the volume change on melting and the thermal expansion and compressibility for liquid T₂ were consistent with those for H₂ and D₂. Impurities such as H₂, HT, DT, and ³He were removed by a technique using an adsorption column of cold activated alumina. Corrections for ³He growth during an experiment were adequate except near the triple point.