A primary aliphatic amine on reaction with nitrous acid in cold...

A primary aliphatic amine on reaction with nitrous acid in cold gives a diazonium salt, but diazonium salt of aliphatic amines are not much stable, so, they dissociate on increasing temperature slightly and gives alcohol with water.

$R - {NH}_{2}\mathop{\to}_{273 ° C}^{{HNO}_{2}\left(aq\right)}{{RN}_{2}}^{+}\mathop{\to}_{{H}_{2}O}^{283 ° C}R - OH + {N}_{2}$