Avoid environmental contamination by Pb. Store quartz crucibles in 20% nitric acid and rinse with deionized water before use. When necessary, crucibles may be boiled with 20% nitric acid before use. Heat platinum crucibles until red hot and boil with 50% (v/v) hydrochloric acid prior to use. Ash products with a high fat content (≥40%), e.g., margarine or lard, with great care to avoid self-ignition. Preash such products according to D(c)(2), even if a programmable furnace is used.