Search for a Discontinuity in the Density of LiquidHe3below 3 mK

The density of liquid ${\mathrm{He}}^3$ along the melting curve below 3 mK and through the transitions to the $A$ and $B$ phases has been studied using a parallel-plate capacitor in a Pomeranchuk cell. It is found that the density varies smoothly in this region with no discontinuity larger than $\frac{\Delta \rho }{\rho }=5\mathrm{}\times {10}^{-5\mathrm{}}$. The existence of a latent heat demonstrates that the $B$ transition is first order; however, the jump in density must be minute.