A computer controlled system for controlling the chemistry of boilers operating on coordinated phosphate ehernistry is described. The salient features of this system is that it uses a feed forward system to compute the future state of the system combined with a unique algorithm for precisely controlling both phosphate level and sodium to phosphate molar ratios simultaneously. This addresses problems with existing systems, in which both phosphate and mole ratio may become seriously out of control. In addition, this system corrects the mole ratios to account for all common additives and expected impurities usually associated with high pressure utility boilers.