Pipet 50 ml bath in a 100 ml PE-cup, adjust with sodium hydroxide
to pH 7 (heavy metals precipitate as hydoxydes and do
not disturb anymore). Prepare two 50 ml comparison samples,
which have the same content as the bath, with chromic acid.
Add 1 ml and 4 ml of the 50 % solution of SurTec 871 II to comparison
sample À and sample Á respectively. Adjust both comparison
samples with sodium hydroxide to pH 7. Put all three
samples quantitatively in each time a 100 ml PE measuring
flask, put them in cold water and cool down to room temperature.
Fill up with demineralised water and mix well.