_
EXPERIMENT 11—4
'
257
—
say
ten small divisions, repeating as rapidly as possible for fteen
minutes.
Be sure torecord the total time from “
zero
”
to the
center
of the activity time at each point. 11. Measure the
_
natural leak.
12. Continue readings every ve minutes for two
hours.
The activity Will be found to be more nearly that of the
natural leak than in the formation curve of experiment 11—2.
_
13. Correct all activities for the natural leak, using the value
'
measured at the end of fteen minutes.
This leak Will probably
_
be large, due to contaminations (perhaps a trace of thoron gas).
Plot activities as ordinates and times as abscissae.
Also plot on
semi—logarithmic paper, With activities on the logarithmic scale
and times on the linear scale.
14. Note and record on this graph
the half life of thorium C and compare With the accepted value.
15. If desired, or if necessary, the experiment_may be repeated,
using the solution of step
7.
The solution Will be su'iciently
active for a second trial for about one day.
EXPERIMENT 11—4
‘
DECAY OF THORIÜM EMANATION
'
,
Charge an emanation electroscope, gure
,
and observe the
.
natural leak.
'If it is too large, the chamber must be opened, sandpapered and cleaned With alcohol or ether” to remove active
deposits. Partially evacuate the chamber, charge theleaf and then.
”introduce a small amount of thorium emanation, stopping as soon
as the leaf begins to fall rapidly. Since the half life of thorium
emanation is comparatively short, observations of
activity
g
must be made quickly. Observe the time
of fall over a small
number of divi‘si0ns, allowing the leaf to continue for a second
—
observation at a different part of the scale. The relative current
_
.
.
changes for the various parts
of the scale maybe found, by observ—
the time required to pass
over theSpecied divisions With a
constant source of ionization‘.
=
_
.
.
.
'
Plot a curve showing the decay of the erhànationwith time
'
and deduce the half period of the thoriùmemanation.
.
—
EXPERIMENT 11—4
'
257
—
say
ten small divisions, repeating as rapidly as possible for fteen
minutes.
Be sure torecord the total time from “
zero
”
to the
center
of the activity time at each point. 11. Measure the
_
natural leak.
12. Continue readings every ve minutes for two
hours.
The activity Will be found to be more nearly that of the
natural leak than in the formation curve of experiment 11—2.
_
13. Correct all activities for the natural leak, using the value
'
measured at the end of fteen minutes.
This leak Will probably
_
be large, due to contaminations (perhaps a trace of thoron gas).
Plot activities as ordinates and times as abscissae.
Also plot on
semi—logarithmic paper, With activities on the logarithmic scale
and times on the linear scale.
14. Note and record on this graph
the half life of thorium C and compare With the accepted value.
15. If desired, or if necessary, the experiment_may be repeated,
using the solution of step
7.
The solution Will be su'iciently
active for a second trial for about one day.
EXPERIMENT 11—4
‘
DECAY OF THORIÜM EMANATION
'
,
Charge an emanation electroscope, gure
,
and observe the
.
natural leak.
'If it is too large, the chamber must be opened, sandpapered and cleaned With alcohol or ether” to remove active
deposits. Partially evacuate the chamber, charge theleaf and then.
”introduce a small amount of thorium emanation, stopping as soon
as the leaf begins to fall rapidly. Since the half life of thorium
emanation is comparatively short, observations of
activity
g
must be made quickly. Observe the time
of fall over a small
number of divi‘si0ns, allowing the leaf to continue for a second
—
observation at a different part of the scale. The relative current
_
.
.
changes for the various parts
of the scale maybe found, by observ—
the time required to pass
over theSpecied divisions With a
constant source of ionization‘.
=
_
.
.
.
'
Plot a curve showing the decay of the erhànationwith time
'
and deduce the half period of the thoriùmemanation.
.
—