Fuming sulfuric acid

Type of fuming sulfuric acid: including pyrosulfuric acid (H2S2O7), dimerized sulfuric acid (H4S2O8) tripolysulfuric acid (H6S3O12), and the like.

Basic traits: colorless or slightly colored thick liquid, capable of emitting asphyxiating sulfur trioxide fumes, which is a sulfuric acid containing excessive sulfur trioxide. 50% or more of sulfur trioxide containing cold crystals. Has a strong water absorption. When it is mixed with the aqueous phase, sulfur trioxide is combined with water to form sulfuric acid. The relative density is about 1.9 (including 20% sulfur trioxide). The freezing point varies greatly with concentration, showing a tendency to rise first and then fall. The freezing point of fuming sulfuric acid containing 20% free sulfur trioxide is 2.5 °C. With the increase of free sulfur trioxide content, when the free sulfur trioxide is 45%, the freezing point reaches 35.0 °C, and then the free sulfur trioxide content is gradually increased. The freezing point will decrease rapidly. Water, organic matter and oxidants are prone to explosions. Very corrosive.

Physical characteristics

Main use: It is used as a sulfonating agent and is also widely used in the manufacture of dyes, explosives, nitrocellulose and pharmaceuticals.

Stability: Extremely unstable, volatile to form sulfuric acid and sulfur trioxide.

Incompatible materials: alkalis, flammable or combustible materials, active metal powders, water, strong reducing agents.

Conditions to avoid contact: reducing agent, metal

Volatilization principle: not only because of the high concentration, but also because the fuming sulfuric acid contains more electrophile sulfur trioxide