Scientia Sinica

46 ; SCIENTIA SINICA Vol, V

The denominator is a sum of two terms and here we may disregard the small difference between fB% and B,, noting that the isothermal partial compressibility 6% — B; is due to volume change in chemical reaction alone. This approximation reduces equation (42) to

a

il GLA po) wT "a0 * BF ) itor: Ce) which is just Liebermann’s equation, equation (14) of reference [12]. From this derivation it becomes apparent that Lieberman’s equation can be a good approximation only for the.case of liquids.

In any case in which chemical reaction takes place so fast that 7, is smaller than the time taken to establish thermal equilibrium, ic., when 1, due to chemical change is less than 1,,, we have to put Bf = B; and only the heat capacity term remains. In this case, equation (43) reduces to”

GIA w? T2 ~ 2002 1-40? 3° _ (44)

VI. Note on THE DEFINITION OF THE COEFFICIENT OF

VoLuME ViscosIry

Our definition for the coefficient of volume viscosity implies that the relaxational processes make the mean pressure p increase above the effective pressure p’ = po +s/B, by an amount that is assumed to be proportional io

; : ds 5 the rate of relaxational compression Ez vis

ot a) Pie) 2 DA)

ds dasa . a2) rea a (45)

It is this added stress that gives rise to the extra dissipation of energy as discussed in reference [4]. When there is no relaxational compression, the dilatational process will, as stated in § I, reduce to a reversible one, the volume

1) This is similar in form to the corresponding Bourgin-Kneser equation for the case of thermal relaxation, viz.,

_ c®# (Cp—Cv) W? T. 200% Gy COGS ae ° CLG; F

which is obtained by substituting (26) into @=p/2A=po/4zv.