Abstract
Requirements of a suitable ref. material are listed and natural and synthetic forms reviewed. Assessments of various methods of preparing homogeneous specimens demonstrates the applicability of physical techniques, such as sifting or mixing with a wetting agent if the constituents are in fine-powder form, and of dry ball-milling for coarser materials. Sorption on Al203 and co-precipitation from a solution on an appropriate substrate are also considered. Preparation and analyses of refs. for Zr--Hf, U, Au, Th, and lanthanide and other elements are particularly described and discussed. 8 ref.--J.R.