Calorimetric search for a tricritical point in mixtures of water, 3-methylpyridine and sodium bromide

Autor:	Jan Thoen, Guido Pitsi, B. Van Roie
Rok vydání:	2003
Předmět:	Phase transition Sodium bromide chemistry.chemical_compound Tricritical point chemistry General Physics and Astronomy Thermodynamics Ising model Calorimetry Physical and Theoretical Chemistry Heat capacity Critical exponent Critical point (mathematics)
Zdroj:	The Journal of Chemical Physics. 119:8047-8051
ISSN:	1089-7690 0021-9606
DOI:	10.1063/1.1607954
Popis:	We investigated the specific heat capacity near the demixing transition of ternary mixtures of water, 3-methylpyridine and sodium bromide as a function of salt concentration. In this system, a crossover from Ising to tricritical behavior caused by the appearance of a new “microheterogeneous” phase was reported from light-scattering measurements [Jacob et al., Phys. Rev. E 58, 2811 (1998)]. We used adiabatic scanning calorimetry, a very sensitive technique for detecting and characterizing phase transitions, to investigate this system and found no specific heat anomaly to be associated with the formation of a new phase. In the one phase region, the critical exponent α is consistent with the Ising value and is incompatible with the tricritical value for all the investigated samples. In the phase-separated region, the values of the exponent are substantially lower and even negative. This is probably caused by the change in salt concentration of the two phases close to the critical point.
Databáze:	OpenAIRE
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