Abstract: An H-type ceramic resonator having two resonating leaves, a connecting leaf for bridging the two resonating leaves to form an H-shape, and electrodes disposed on at least both surfaces of the resonating leaves. The resonator has a dimensional relationship which falls within the following equities:B.sub.2 /B.sub.3 =4 to 6,B.sub.1 /B.sub.3 =2 to 4, andL/B.sub.1 =5 to 6wherein L is a length of each of the resonating leaves, B.sub.1 is a width of each of the resonating leaves, B.sub.2 is a distance between the two resonating leaves, and B.sub.3 is a width of the connecting leaf.

Abstract: A method for economically concentrating an acrylamide aqueous solution by catalytic hydration without substantial deterioration in the product. According to the method, an acrylamide aqueous solution obtained from catalytic hydration, is concentrated by distillation while maintaining the solution in good contact with at least 0.1 mole. or more of air per mole of water distilled from the acrylamide aqueous solution.

Abstract: There is disclosed a method for handling acrylamide aqueous solutions with safety wherein acrylamide aqueous solutions obtained through catalytic hydration reaction of acrylonitrile are handled using utensils made from phenol resin, polyethylene, polypropylene, polyvinylchloride resin or fluorine-containing resin or glass or using such utensils that are provided with linings formed by these materials.