We have measured a change in specific volume of (0.5 ± 0.2) × ${10}^{-4\mathrm{}}$ ${\mathrm{cm}}^3$/g at the nematic-smectic-$A$ transition of $\mathrm{N}-p-\mathrm{cyanobenzylidene}-p-\mathrm{octyloxyaniline}$. The order of this transition has recently been subject to dispute. On the basis of our data, we conclude unambiguously that it is of first order as is expected from theoretical analysis.

• Received 25 March 1974

DOI:https://doi.org/10.1103/PhysRevLett.32.1406