Hmm, we use the 2.22e12 for cpm to curie calculations. I'm not sure where the 3.7e10 fits in. I've gotten lazy though - I've been doing it so long I just stick the numbers in a calculator without thinking about the unit conversions. But you know, I think we assume that cpm to dpm counting is efficient, and that is not the case for all nuclides. In some cases, cpm=/=dpm, it's cpm=N*dpm, where N=some coefficient to describe efficiency of the counter. That might be where the 3.7e10 comes in.

We usually use a set amount of curies per fixed volume in a reaction tube, then calculate from that how many nanomoles are consumed in a catalytic reaction.