A technique whereby the element to be analysed is quantitatively separated and transformed to a well defined and very pure chemical compound which is accurately weighed and related to the stoichiometric quantity of the element to be analysed in the compound. At the Safeguards Analytical Laboratory, ignition gravimetry is used for determining U and Pu concentrations in oxides by converting them to stoichiometric U₃O₈ for U and PuO₂ for Pu