... Page 6. HELVETICA CHIMICA CTA - Vol. 74 (1991) 1747 ... NH, soln. and filtered. The volume of the filtrate was reduced to 30 ml and applied to an XAD-4 column (2 x 20 cm). H 2 0 (200 ml) removed inorg. ... Page 7. 1748 HELVETICA CHIMICA ACTA -Val. 74 (1991) ...