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Along a first-order coexistence curve,At a critical point the two phases merge, their entropy jump vanishes, and the latent heat tends to zero.

Molar mass is mass per amount of substance, commonly expressed in $\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$. For chain counts $n_i$ and chain molar masses $M_i$, the number average is $M_n={\sum }_i{n}_i{M}_i/{\sum }_i{n}_i$. Relating it to a degree of polymerization requires a defined unit-mass convention and end-group accounting.

Size-exclusion chromatography separates dissolved molecules using porous columns. Elution depends on molecular size in the chosen solvent; calibration supplies an estimate of molar mass. A trace calibrated with another polymer does not automatically give absolute molar masses or a number-count probability distribution.