How `3^(@)` amine reacts with nitrous acid ?

Explanation

`3^(@)` aliphatic amines react with nitrous in cold to form salts which decompose on warming to give nitrosoamine and alcohol.
`R_(3)N+HNO_(2)rarrR_(3)NHNO_(2)overset("Warm")rarrunderset("Nitrosoamine")(R_(2)N-N=O)+underset("Alcohol")(ROH)`
`3^(@)` aromatic amines react with nitrous acid to give coloured substituted nitroso compounds.
These undergo electrophilic substitution of nitrosoanium ion at the p-position of the benzene ring.