5.10 Liquid Geiger–Müller Counter
79
Fig. 5.15 A schematic graph
showing the exponential
variation in the activity of
same quantity of long-lived
radioactive isotope measured
in liquids of different
density, keeping the total
amount of liquid same in a
liquid G.M. counter
D 1
D 2
A 1
A 2
Density of liquid
Activity of sample
liquid. Such density correction is done in the following manner. Same quantity of
a radioactive substance (either liquid or solid) is added to the different solvents
of different densities, but the total volume of mixture is maintained to 10.0 ml, in
each case. These solutions are counted in the liquid G.M. counter. Activity (i.e.,
count rate) is plotted against density of the liquid (Fig. 5.15). It is observed that
the activity of the sample is not similar for all solutions, instead it decreases with
increase in density of liquid.
The graph shown in Fig. 5.15 suggests that whenever the activity of a radioactive
material present in more than two solutions are to be compared, one should either
use a specific solvent so that there is no change in density or make necessary
corrections in the activity by normalizing the count rate to a fixed density value.
This type of correction is generally required in solvent extraction, where activities are distributed between two solvent phases (i.e., the activities in organic and
water phases). In such type of experiments, it is important to make the density
correction as discussed here.
A radioactive tracer of known specific activity is added equally into two liquids
(of different densities) having equal volume. Activities of both are measured by
a liquid G.M. counter. Let us assume that “A 1 ” is count rates, obtained with a
radioactive material in 10 ml of a liquid of density D 1 . Similarly, lets assume that
we get a count rate of “A 2 ” of same radioactive material of same quantity added
in 10 ml of another liquid of density D 2 . Since known amount of activity was
added to each solvent (A 0 ), the fractional loss of activities in each solvent are
calculated as follows:
79
Fig. 5.15 A schematic graph
showing the exponential
variation in the activity of
same quantity of long-lived
radioactive isotope measured
in liquids of different
density, keeping the total
amount of liquid same in a
liquid G.M. counter
D 1
D 2
A 1
A 2
Density of liquid
Activity of sample
liquid. Such density correction is done in the following manner. Same quantity of
a radioactive substance (either liquid or solid) is added to the different solvents
of different densities, but the total volume of mixture is maintained to 10.0 ml, in
each case. These solutions are counted in the liquid G.M. counter. Activity (i.e.,
count rate) is plotted against density of the liquid (Fig. 5.15). It is observed that
the activity of the sample is not similar for all solutions, instead it decreases with
increase in density of liquid.
The graph shown in Fig. 5.15 suggests that whenever the activity of a radioactive
material present in more than two solutions are to be compared, one should either
use a specific solvent so that there is no change in density or make necessary
corrections in the activity by normalizing the count rate to a fixed density value.
This type of correction is generally required in solvent extraction, where activities are distributed between two solvent phases (i.e., the activities in organic and
water phases). In such type of experiments, it is important to make the density
correction as discussed here.
A radioactive tracer of known specific activity is added equally into two liquids
(of different densities) having equal volume. Activities of both are measured by
a liquid G.M. counter. Let us assume that “A 1 ” is count rates, obtained with a
radioactive material in 10 ml of a liquid of density D 1 . Similarly, lets assume that
we get a count rate of “A 2 ” of same radioactive material of same quantity added
in 10 ml of another liquid of density D 2 . Since known amount of activity was
added to each solvent (A 0 ), the fractional loss of activities in each solvent are
calculated as follows: