Pressure-Volume-Temperature Relations in Liquid and Solid Tritium

PVT relations in liquid and solid T(2) 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(m) 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 k(1) = 6−9×l0(−2)h(−1). By extrapolation, the ortho and para forms differed by ΔP(m)~6 bar and ΔV(lm)~0.5%. Measurements of the volume change on melting and the thermal expansion and compressibility for liquid T(2) were consistent with those for H(2) and D(2). Impurities such as H(2), HT, DT, and (3)He were removed by a technique using an adsorption column of cold activated alumina. Corrections for (3)He growth during an experiment were adequate except near the triple point.