Abstract: Novel sizing comprising an aqueous mixture of ammonia, an ammonium salt of formic acid, and a rosin that is modified with from about 5 to 50 percent, based on the weight of the rosin, of an organic acidic compound selected from the group consisting of an .alpha.,.beta.-unsaturated organic acid, an anhydride thereof, and their mixtures. In one embodiment, the ammonia and ammonium salt are produced as the reaction product of urea and formic acid. A method of making the sizing compositions and paper which is sized with the sizing compositions are also provided.

Abstract: Novel sizing compositions comprise an aqueous mixture of the reaction product of urea with selected Lewis acid, and a rosin that is modified with from about 5 to 50 percent based on the weight of the rosin, of an organic acidic compound selected from the group consisting of an .alpha.,.beta.-unsaturated organic acid, an anhydride thereof, and their mixtures. The selected Lewis acids which can be employed are sulfuryl chloride, chlorosulfonic acid, thionyl chloride, benzenesulfonyl chloride, benzenesulfonic acid, ortho- or para-toluenesulfonyl chloride, and ortho- or para-toluenesulfonic acid. Methods for making the sizing compositions and paper which is sized with the sizing compositions are also disclosed.