Cubic expansion coefficient negative values

At constant concentration, when the temperature dependence is examined, usually a m, T)>a m. -,T) if T >T but the difference between them decreases rapidly with increasing T and sometimes the inverse behaviour is observed at high temperatures, as for example in the case of disodium Itydrogen citrate (Fig. 5.23). Differences in cubic expansion coefficients, A a nf,T)= o vr, )- a J T), have positive values, but they strongly decrease with T. Above temperature of about 60 °C, Aa(m T) values can be negative or positive, but if positive they are nearly constant (Fig. 5.24). The apparent molar volumes having the con-... 

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