Avoid environmental contamination by Pb.Store quartz crucibles in 20 % HNO3 and rinse with deionized water before use. When necessary, crucibles may be boiled with 20 % HNO3 before use.Heat platinum crucibles until red hot and boiled with 50% (v/v) HCl prior to use.Ash products with a high fat content ,e.g., margarine or lard, with great care to avoid self-ignition. Pre-ash such product according to D(c)(2),even if a programmable furnace is used.