Chloropicrin is prepared by heating chloroform with concentrated nitric acid.
$\mathrm{CHCl}_3+\mathrm{HONO}_2 \rightarrow \mathrm{CNO}_2^{-} \mathrm{Cl}_3+\mathrm{H}_2 \mathrm{O}$
chloropicrin
Related Theory
Chloropicrin (Trichloro(nitro)methane) is also prepared by the reaction of nitromethane with sodium hypochlorite.