5. Heat on 140 C hotplate until volume is reduced to about 0.5 mL.
6. Repeat two more times using 2 mL conc. HNO
3
and 1 mL 30% H
2
O
2
each time.
7. Heat on 140 C hotplate until ca. 0.5 mL liquid remains.
8. Whensample is dry, rinse the watchglass and walls of the beaker with 3 to 5 mL 10% HNO
3
.Allow
the solution to evaporate to dryness.
9. Cool each beaker and dissolve the residues in 1 mL conc. HNO
3
.
10. Transfer the solution quantitatively to a 10-mL volumetric flask and dilute to volume with distilled
water.