Reston stable isotope lab (RSIL): reference VSMOW

Photo of glass ampoules of reference material VSMOW. This reference material (RM) is an international measurement standard that defines the zero of the δ² H and δ¹⁸O Vienna Standard Mean Ocean Water–Standard Light Antarctic Precipitation (VSMOW-SLAP) isotope scales in water and in all other hydrogen-bearing substances and in selected oxygen bearing-substances.