Mix 1000 mg of very finely powdered samp領(lǐng) material with 1.5 g magnesium oxide and 5 g sodium carbonate and heat at 900°C for about 30 minutes. Moist the cooled sinter cake with a little water GR, pulverise and transfer into a 150 ml glass beaker, with 50 ml of water GR and 1 drop of ethanol. Heat the mixture on the steambath for 30 minutes, cool to room temperature and filter through a fluted filter into a 100 ml standard volumetric flask. Fill up to volume with water GR and mix well.