Graham D. Foster Jessica A. Hopple 1995 <p>Bright-orange floating matter (possibly algae) has been observed in the United States supply&nbsp;of some ampoules and in one of two 10-L primary glass storage flasks of the isotopic&nbsp;reference water VSMOW (Vienna Standard Mean Ocean Water). Within experimental error,&nbsp;ampoules with and without this orange matter are identical in stable hydrogen and oxygen&nbsp;isotopic composition. Thus, the North American supply of VSMOW has not been altered in&nbsp;isotopic abundance and remains fully functional as a primary isotopic reference material.</p> application/pdf en Audit of VSMOW distributed by the United States National Institute of Standards and Technology text