a 12 percent ferric iron content are needed to set one pound of dry rosin size this corresponds to 0 29 pounds of ferric iron per pound of dry rosin size as compared with 2 pounds dry alum per pound of rosin size for increased freeness of the stock 0 6 2 4 pounds of ferric iron per ton of paper were evaluated corresponding to a feed rate of 10 40 pounds of ferriclear per ton of paper this evaluation demonstrated substantial increases in freeness of the stock the iron salt may be added to the stock as a solution a solid or in a stream of water that is added to the stock as will be shown from the examples below the sequence for combining the rosin size and the retention agent with the stock is unimportant in general either the retention agent or the rosin size may be added to the stock first without deleterious effect upon the water repellence and other characteristics of the resulting paper specific modified rosin sizes however may have characteristics that require that either the size or the retention agent be added first to produce the desired retention and other effects and certain equipment may also require or prefer a given sequence of addition the point at which the iron salt will be added will vary depending upon the particular paper being made and the fabrication process employed but should in all cases be prior to the sheet forming area factors related to this determination include the type of size being used the presence of substances that interfere with the retention of size other desired effects the type of paper being manufactured the type of stock being used and the equipment employed tests examples i vi were run on ultrex 300 austell box.