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1. Carefully weigh out 0.1 g of lead sulphate into each of 2 plastic scintillation vials
2. Add 2 cm3 of 35S-labelled lead sulphate solution into each
3. Place caps on vials and shake vigorously for 15 min
4. Filter using a Buchner funnel and filter paper
5. Pipette 0.5 cm3 of each filtrate onto 2 aluminium planchettes
6. Carefully transfer the planchettes using a tray lined with absorbent tissue to the wooden block beneath the infrared lamp in the fume hood
7. Dry under the IR lamp taking care not to leave them too long in case of fire
8. Transfer the dried planchettes to the Geiger counter on a tray
9. Count both on shelf 2 of the Geiger counter – count for 1 min, repeat this 3 times and average the counts obtained
10. Pipette 0.5 cm3 of original 35S-labelled lead sulphate solution (without the addition of lead sulphate powder) onto 3rd planchette , dry and count as above
11. Calculate the surface area, which should give a value of 104 – 105 cm2 g-1