heating the covered tube for 1 h at 858C in a water
bath, then the cover was removed and the volume
reduced to a few ml. A further aliquot (10 ml) of
solution C was added. The tube was heated again
(858C for 1 h) then the watch glass was removed and
the volume reduced to a few ml. 50 ml of solution D
was added to the cool residue, which was extracted as
described above.