Newton, MA-based Morehouse-Cowles has announced the addition of several new representatives to sell its line of dissolvers, dispersers, media mills and mixers to the eastern U.S. and Canada.      The new representatives are: Armac (ME, NH, MA, RI, VT, CT, NY); Chemaction (Quebec); Chemi International, Inc. (FL); Divtech Equipment Co. (OH, PA, WV, IN); The Fluid Equipment Group (NC, SC); GEMCO (AL, GA, NC, SC, MS, TN, VA; J&B Meter and Pump Service, Inc. (MI); LDC Incorporated (AL, GA, KY, ...