Ilya Bindeman's stable isotope lab
Jim Watkins' or one of the other second floor labs
TSA's various shops, hanging with mi paesani
Isotope ratio mass spectrometry
† Bringing us to 55 of 82‡ stable elements in the Soltherm basis set. The other items being metastable acetate, oxalate, succinate, malonate, aqueous CH4, H2, N2, and NH3, radioactive UO2+ and Pm+3, and alternate redox component O2 - redox state is defined by either paired sulfate-sulfide or H2O-O2. A legacy from the era of 16-bit operating systems, when use of sulfide for an oxidizing system, or O2 for a reducing system, might cause an array underflow — or that was claimed to be the case but will never be verified. Since water must be present and sulfate is so common, basis components sulfide and O2 were hard coded to be mutually exclusive. Pick one.
‡ Bismuth-209 undergoes α-decay to 205Tl with a half-life of 2.01x1019 years, or, ~1.46x1009 times the 1.38*1010 or so year age of our observable universe. To not be a pedant but only in this one case, bismuth is deemed stable. So 82 rather than 81.