What is diazotisation

Explanation

The reaction/process of converting aromatic primary amines into diazonium salts by treatment with a solution of nitrous acid (produced, in situ, by the action of dilute HCl on sodium nitrile) at 273-278 K is called diazotisation, for example,
`NaNO_(2)+HCl to HNO_(2)+NaCl`
`underset("Aniline")(C_(6)H_(5)-NH_(2))+underset("Nitrous acid")(HNO_(2)) +HCl underset(("Diazotisation"))overset(273-278K)to underset("Benzenediazonium chloride")(C_(6)H_(5)-overset(+)(N)-=NCl^(-))+2H_(2)O`