Can anyone recommend a source of hydrogen reference gas with a del D SMOW reasonably close to 0? At the moment I'm using a reference gas with del D < -400. Thanks very much for your help. Jane ********************************************* Dr. Jane L Alexander Department of Earth and Planetary Sciences Harvard University 20 Oxford Street phone: (617) 496 5894 Cambridge fax: (617) 496 4387 MA 02138 e-mail: [log in to unmask]