The Collaborative International Dictionary of English v.0.48:

Dulcify \Dul"ci*fy\, v. t. [imp. & p. p. Dulcified; p. pr. &
   vb. n. Dulcifying.] [L. dulcis sweet + -fy: cf. F.
   dulcifier.]
   1. (Pharm.) To sweeten; to free from acidity, saltness, or
      acrimony. --Wiseman.
      [1913 Webster]

   2. Fig. : To mollify; to sweeten; to please.
      [1913 Webster]

            As she . . . was further dulcified by her pipe of
            tobacco.                              --Hawthorne.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dulcify
    v 1: make sweeter in taste [syn: sweeten, dulcify,
         edulcorate, dulcorate] [ant: acetify, acidify,
         acidulate, sour]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "dulcify":
   allay, appease, calm, calm down, candy, compose, conciliate, cool,
   cradle, defuse, ease, edulcorate, even out, gentle, glaze, honey,
   hush, lay, lay the dust, lull, mollify, mull, pacify, placate,
   pour balm into, pour balm on, propitiate, quell, quiet, rest, rock,
   rock to sleep, saccharify, smooth, smooth down, smooth over,
   smoothen, soothe, stabilize, steady, still, subdue, sugar,
   sugar off, sugarcoat, sweeten, tranquilize