Comment on "Two New Carbonate Stable Isotope Standards"

Friedman et al (1) propose that NBS 19 calcium carbonate substitute for PDB. This is in apparent conflict with the recommendation of the September 1976 consultants' meeting convened by the International Atomic Energy Agency on stable isotope standards. Furthermore, Friedman et al suggest ɛ-values be adopted for NBS 19 that do not take into account the ɛ-values of NBS 20 (Solenhofen limestone). We believe that adoption of these proposals may lead to confusion in the stable isotope literature and to lack of correspondence between historic and future isotopic results.
In sharp contrast to the results of Friedman et al (1), we find NBS 20 to be a satisfactory reference material if it is handled properly.