Thank you for reporting, we will resolve it shortly
Q.
Lassaigne's test for the detection of nitrogen
fails in
AIPMTAIPMT 1994
Solution:
Lassaigne's test is given by only those
compounds which contain both carbon and
nitrogen. When compounds containing C and N
heated with sodium, then it form NaCN which is
easily detected by FeCl$_3$
$ \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, Or$
Some compounds live hydrazine (NH$_2$ . NH$_2$)
although contain nitrogen but they do not respond
Lassaigne's test because they do not have any
carbon and hence, NaCN is not formed.