High-resolution measurements of the molar volume, V,
measured as a function of temperature at two different
pressures allowed the calculation of the isobaric thermal expansion
coefficient, α
p
(T), and
isothermal
compressibility coefficient,
β
T
(T). Critical exponents
for observed singularities in both thermodynamic
quantities were found. It was confirmed that the same critical
exponent α, usually assigned to heat capacity,
describes singularities of the thermal expansion and the isothermal
compressibility coefficients. Two
compounds from the two different homologous series, nCB and
m̄S5, were studied. V(T) and
βT(T) variations
in 8CB showed a continuous phase transition with the effective critical
exponent α = α‘ = 0.32 ± 0.02. For
S5 a weakly
first-order transition with a volume jump ΔV = 0.127 ±
0.001 cm3/mol (ΔV/V = 2.6 ×
10-4)
was observed and an exponent α = α‘ = 0.50 ± 0.02 was
found.
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