t is the decay time. (This is the number of hours from the time the sample was removed from the reactor to the time it was counted, or 5 hours.)
Therefore, A₁, the activity of arsenic-76 produced in the sample at the time of removal from the reactor,
=
| 4.4 counts per second |
| 0.010 × 0.41 |
= 1200 disintegrations per second
3. Calculation of arsenic concentration in the sample.
We use the equation:
Concentration in parts per million =
| A₁ |
| A₀ × W |
where A₁ and A₀ were determined above and W is the weight of sample analyzed or 300 micrograms (0.0003 gram).