Robin, > "There another possibility that keeps nagging at me.... It occurs to me that > perhaps there is something like CHy, with a strong bond between the Hy and > the C, which would have a mass of 13, and would pass for C13.
Well - the problem is that the (hypothetical) molecular ion 12C(Hy)+ would not have the identical mass of atomic 13C+, but in fact would be slightly less. The instrument used - so I am told - should be of a precision to be able to differentiate the two if it were calibrated to do so, and if the operator was so instructed to look for it. Apparently two different instruments were used, and the results with the most precision was done by an outside contractor and specialist who perhaps should have noticed a variance. This is not clear however. The circumstances and the identity of this carbon residue, fully half of it, leans toward it really being 13C -- but OTOH it would be very reassuring to know that Mizuno was aware of this possibility and made the necessary calibrations - since the small difference might not be apparent if one were not expecting it. Either way it is a miracle - minor miracle (Mills) or major miracle (13C)... Jones
