A few notes for the Na-Complexation lab:

  - As D2O is somewhat pricey, use a (nominally) 10:1 H2O/D2O mixture
    when making your solutions, rather than pure D2O.  The NMR
    spectrometer will still be able to lock and shim on this mixture
    if you choose "H2O/D2O" from the solvent menu when locking.

  - Rather than weighing the 18-Crown-6 for each sample, try to
    prepare the samples by serial dilution.

  - A typical NMR sample is about 0.75 mL.