Sulfonamide is also called p-aminobenzene sulfonamide, sulfonamide, p-aniline sulfonamide and p-sulfonamide aniline. The precipitates from the ethanol aqueous solution are white leaf shaped crystals or crystalline powders, odorless, slightly bitter first and then sweet, and discolor when exposed to light. The relative molecular weight is 172.22. The relative density is 1.08. The melting point is 165-166 ℃. It is insoluble in benzene, ether and chloroform, but soluble in water (g/l): 2.6 at 10 ℃, 7.5 at 25 ℃, 17.0 at 40 ℃, 40.0 at 60 ℃, 477 at 100 ℃. Chemicalbook is also soluble in ethanol. It is soluble in 1g per 37ml of ethanol, 1g per 5ml of acetone, glycerin, propylene glycol, hydrochloric acid and sodium hydroxide (potassium hydroxide) solutions. Sulfonamide water solution litmus test paper is neutral, and 0.5% of water solution pH=5.8~6.1. The color darkens under light.