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220
Sample c
(mg/ml)
c
(g/ml)
t
(sec)
h
sp
/c
(ml/g)
0
0
192.0 -
1
0.2
0.0002 240.1 1 252.6
2
0.4
0.0004 296.2 1 356.8
3
0.6
0.0006 360.1 1 459.2
4
0.8
0.0008 432.0 1 562.5
First,
η
sp
/c is calculated for each concentration and results are plotted as a
function of c:
According to Huggins’ equation the data should form a straight line, with the
intrinsic viscosity as intercept and k’
[η]
2
as slope. In practise, a linear
regression is used. In the example above
[η]
= 1150 ml/g, and Huggins’
constant (k´) becomes 516059/1150
2
= 0.39. Knowing Huggins’ constant
allows the calculation of [
η
] for a single concentration. This will be used in the
laboratory course.
6.1.3.
Intrinsic viscosity of
solid
spheres
The first insight into the intrinsic viscosity comes from Einstein’s (yes, him!)
studies of the dilute solution properties of microscopic, solid spheres
dispersed in a liquid. He found for very low concentrations (dilute solutions)
that:
y = 516059x + 1149.7
0
500
1 000
1 500
2 000
0 0.0002 0.0004 0.0006 0.0008 0.001
Kons. (g/ml)
η
sp
/
c