the graft copolymerization of 4-vinylpyridine (4-vp) on to unmodified cellulose and partially carboxymethylated cellulose (pcmc) initiated by ceric ammonium nitrate (can) in dilute nitric acid was carried out. the grafting parameters, graft yield (g), total conversion (c//t) and grafting efficiency (ge), were studied as functions of the rate of stirring and of the total nitrate ion concentration. in the case of unmodified cotton, g and c//t curves were almost identical in shape; both curves recorded a maximum value at low revolutions per minute and then decreased steadily with increasing agitator speed. ge kept constant over the range studied when 4-vp was copolymerized on to pcmc, g showed a minimum at about 200 rpm. total conversion behaved similarly. ge reached greater values for copolymerization with pcmc than with cotton. the ce(iv) consumption during grafting was almost complete in both cases. it was shown for both cellulosic substrates employed that g and c//t decreased with an increase in the nitrate ion concentration by addition of sodium nitrate. the effect of other inorganic salts was also examined. (author abstract) 26 refs