  We have measured the reaction rates of trapped, buffer gas cooled Th$^{3+}$
and various gases and have analyzed the reaction products using trapped ion
mass spectrometry techniques. Ion trap lifetimes are usually limited by
reactions with background molecules, and the high electron affinity of multiply
charged ions such as Th$^{3+}$ make them more prone to loss. Our results show
that reactions of Th$^{3+}$ with carbon dioxide, methane, and oxygen all occur
near the classical Langevin rate, while reaction rates with argon, hydrogen,
and nitrogen are orders of magnitude lower. Reactions of Th$^{3+}$ with oxygen
and methane proceed primarily via charge exchange, while simultaneous charge
exchange and chemical reaction occurs between Th$^{3+}$ and carbon dioxide.
Loss rates of Th$^{3+}$ in helium are consistent with reaction with impurities
in the gas. Reaction rates of Th$^{3+}$ with nitrogen and argon depend on the
internal electronic configuration of the Th$^{3+}$.
