Physical Chemistry of Foods

Table 5.2 also gives examples of the viscosity of some aqueous solutions. It
is seen that most solutes increase the viscosity, although the increase is quite
small for KCl. A 20%aqueous ethanol solution is seen to have a distinctly
higher viscosity than each of the pure liquids; this must be related to the
contraction—hence a decrease in free volume—occurring upon mixing of
the two liquids. Also for solutions it is useful to have a look at the effects of
dispersed particles (or molecules).

TABLE5.2 Viscosity of Some Fluids and Solutions

Material Temperature ( 8 C)

Z

mPa?s

ðZ=rÞa

mm^2 =s

Gases

Dry air 20 0.018 15

70 0.021 20

Liquids

Water 0 1.79 1.79

20 1.00 1.00

40 0.65 0.66

100 0.28 0.29

Diethyl ether 20 0.23 0.32

Ethanol 20 1.20 1.53

Glycerol 20 1760 1400

n-Pentane 20 0.24 0.38

n-Decane 20 0.92 1.26

n-Hexadecane 20 3.34 4.32

Triglyceride oil 10 125 135

20 75 82

40 33 37

90 8 9

Aqueous solutions,20%

Ethanol 20 2.14 2.21

Glycerol 20 1.73 1.66

Glucose 20 1.90 1.76

Sucrose 20 1.94 1.80

KCl 20 1.01 0.89

NaCl 20 1.55 1.35

Calculatedb 20 1.82

aThis is called the kinematic viscosity.

bAccording to Eq. (5.11), forj¼ 0 :2,jmax¼ 0 :65 and½ZŠ¼ 2 :5.