Method	Acid system			The solution color	Residue color	Dispelling effect
Method	HNO₃	HF	H₂O₂	The solution color	Residue color	Dispelling effect
1	5 mL	2 mL	1 mL	Light yellow	Light gray	Completely
2	3 mL	3 mL	1 mL	Light yellow	Gray	Incompletely
3	2 mL	5 mL	1 mL	Colorless	Gray and black	Incompletely