  We have investigated the chemistry of dense interstellar clouds and found new
bistable solutions in the nitrogen and carbon chemistries. We identify the
autocatalytic processes that are present in the pure, reduced, chemical
networks and, as previously found for oxygen chemistry, that He$^+$ plays an
important role.
  The applicability of these results to astronomical environments is briefly
discussed. The bistable solutions found for carbon chemistry occur for low
densities and high ionization fractions that are not compatible with that found
cold, dense clouds. Bistability in the pure nitrogen chemistry occurs for
conditions that are relevant for prestellar cores in which significant CO
depletion has taken place. We conclude that several autocatalyses are embedded
in gas-phase interstellar chemistry and that many more are potentially present.
