Sulfanilic acid
Sulfanilic acid is a grey crystalline solid produced from sulfonation
Aromatic sulfonation
Aromatic sulfonation is an organic reaction in which a hydrogen atom on an arene is replaced by a sulfonic acid functional group in an electrophilic aromatic substitution.-Mechanism:...

 of aniline
Aniline, phenylamine or aminobenzene is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane...

It readily forms diazo
Diazo refers to a type of organic compound called diazo compound that has two linked nitrogen atoms as a terminal functional group. The general formula is R2C=N2. The simplest example of a diazo compound is diazomethane...

 compounds and is used to make dyes and sulpha drugs
Sulfonamide (medicine)
Sulfonamide or sulphonamide is the basis of several groups of drugs. The original antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame...


Sulphanilic acid exists as a zwitterion
In chemistry, a zwitterion is a neutral molecule with a positive and a negative electrical charge at different locations within that molecule. Zwitterions are sometimes also called inner salts.-Examples:...

, and has an unusually high melting point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

. It is used as a standard in combustion analysis
Combustion analysis
Combustion analysis is a method used in both organic chemistry and analytical chemistry to determine the elemental composition of a pure organic compound by combusting the sample under conditions where the resulting combustion products can be quantitatively analyzed...

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