No. of Trials

Reagent volumes (mL) HNO₃:HClO₄

Digestion

temperature (˚C)

Digestion time (min)

Observation

1

3:1

120

60

Deep yellow solution

2

2:3

150

90

Deep yellow solution

3

3:2

180

100

Yellowish solution

4

2:4

200

120

Yellowish solution

5

4:1.5*

210*

150*

Clear colorless solution

7

5:2

210

170

Clear colorless solution

8

6:1

240

170

Clear colorless solution

9

5:3

250

200

Clear colorless solution