Division 1 Procedure

Weigh out 10 g tomato powder or flakes to within 0,01 g into a 300-ml beaker. Add 200 ml water. Mix well. Leave to settle for 10 minutes. Carefully pour off supernatant. Repeat the operation a second time. Collect solid residue on an ashless ultra-fast filter. Roast in a porcelain incineration dish. If necessary, mix with a little distilled water and return to furnace until the ash is white.

Mix with 10 cm³ nitric acid (d = 1,4) diluted to half. Heat very gently and collect precipitate on an ashless pleated filter, dry and roast in a tared crucible (m°). If necessary mix as before with a little distilled water and roast once more if ash is not white. Weigh crucible (m).