Question

Which one of the following cation will give a blue coloured ash when a piece of filter paper dipped in a solution containing its salt and `Co(NO_3)_2` is burned?
A. `Cu^(2+)`
B. `Mg^(2+)`
C. `Al^(3+)`
D. `Zn^(2+)`

Answer 1

The filter paper ash test is substitute for cobalt nitrate charcoal cavity test. Double oxide `Al_(2)O_(3).CO O` formed is blue in colour.