9-6. A 131I standard solution was obtained from the National Bureau

of Standards (NBS). The following information was supplied concerning

the solution: assay of 131I at 8 A.M., January 1, 2.09 ×

104 dps/mL } 2%. On January 15 at 8 A.M., a sample of 131I was

counted. This sample had been obtained from a shipment of 131I

in the following manner: 20 λ (I λ = 1μL) of the shipment was

diluted in a volumetric flask to 25 mL; 100 λ of this solution

was diluted to 10 mL; and 50 λ of this solution was withdrawn,

mounted on Mylar, dried, and counted. The dried sample provided

a count rate of 4280 cpm corrected for background. At the same

time (8 A.M., January 15), a 50-λ sample of the NBS standard 131I

solution was mounted, dried, and counted in the same manner.

The count rate for the standard sample was 1213 cpm corrected

for background.

a. What was the specific activity (millicuries per milliliter) of the

131I shipment at the time the sample from the shipment was

counted?

b. What was the total correction factor between the count rate and

the activity of the system used to count 131I mounted on Mylar?