Sulfanilic acid:
Sulfanilic acid, also known as 4-aminobenzenesulfonic acid, is an organic compound with the molecular formula C6H7NO3S. It is a white crystalline solid that is highly soluble in water. Sulfanilic acid is widely used in various industries, including pharmaceuticals, dyes, and cosmetics, due to its versatile properties.

Structure and Properties:
Sulfanilic acid consists of a benzene ring attached to both an amino group (-NH2) and a sulfonic acid group (-SO3H). The amino group is located in the para position with respect to the sulfonic acid group. This chemical structure gives sulfanilic acid its unique properties.

Uses:
Sulfanilic acid has numerous applications across various industries:

1. Pharmaceuticals: It is commonly used as an intermediate in the synthesis of various pharmaceutical drugs. It serves as a starting material for the production of sulfa drugs, which are antibiotics used to treat bacterial infections.

2. Dyes: Sulfanilic acid is widely employed in the dye industry for the production of azo dyes. Azo dyes are synthetic dyes that contain an azo group (-N=N-). Sulfanilic acid acts as a diazonium salt precursor in the synthesis of azo dyes, imparting color to fabrics, plastics, and other materials.

3. Cosmetics: Sulfanilic acid is utilized in the formulation of various cosmetic products, including hair dyes and colorants. It provides vibrant and long-lasting color to cosmetic formulations.

4. Chemical Analysis: Sulfanilic acid is used as a reagent in various chemical tests and analyses. It is commonly employed in the detection and determination of nitrites and nitrates. The reaction between sulfanilic acid and nitrites produces a diazonium salt, which can be further coupled with other reagents to form a colored compound.

5. Photography: Sulfanilic acid is sometimes used in photographic developing solutions. It helps to stabilize the developing process by preventing oxidation reactions and preserving the integrity of the image.

Overall, sulfanilic acid is a versatile compound with a wide range of applications in various industries. Its unique chemical structure and properties make it an important ingredient in the synthesis of pharmaceuticals, dyes, cosmetics, and chemical reagents.

It is an off-white crystalline solid which finds application in quantitative analysis of nitrate and nitrite ions. It exists as a zwitter ion.
Formula: C6H7NO3S