Ammonium citrate, a salt formed from citric acid and ammonia, is a compound characterized by its unique chemical and physical properties. Understanding these attributes is fundamental to appreciating its widespread use across various industries, from food and beverages to pharmaceuticals and industrial cleaning. This exploration aims to shed light on the core characteristics that make ammonium citrate such a valuable chemical entity.

Chemically, ammonium citrate is a salt of a weak acid (citric acid) and a weak base (ammonia). This composition contributes to its buffering capabilities, allowing it to maintain a relatively stable pH in aqueous solutions. The presence of carboxylate groups from the citric acid molecule also imparts chelating properties, enabling it to form stable complexes with metal ions. This dual functionality is key to its effectiveness as a pH regulator and a metal ion sequestrant.

In terms of physical appearance, ammonium citrate is typically a white crystalline powder or granules. It is generally odorless, though some forms may exhibit a slight ammoniacal odor. Its solubility in water is a significant advantage; it readily dissolves, forming clear solutions. The specific solubility can vary slightly depending on the exact composition and temperature, but its high water solubility facilitates its incorporation into liquid formulations.

The pH of ammonium citrate solutions is generally slightly acidic to neutral, depending on the ratio of citric acid to ammonia and the concentration. This characteristic makes it useful for pH adjustment in applications where a mild acidulant or buffer is required, such as in cosmetics, certain food products, and pharmaceutical preparations. The precise pH range it can effectively buffer is a crucial factor in its application as a pH regulator.

The molecular structure of ammonium citrate is derived from citric acid, which is a tricarboxylic acid with a hydroxyl group. The ammonium ions (NH4+) are associated with the deprotonated carboxylate groups. The ammonium citrate chemical formula is typically represented as C6H11NO7 for diammonium hydrogen citrate, reflecting the salt formation. Its molecular weight and other physical constants, such as melting point (often with decomposition), are important parameters for manufacturers and researchers.

Ammonium citrate is known to be hygroscopic, meaning it can absorb moisture from the air. Therefore, proper storage in tightly sealed containers is essential to maintain its quality and prevent caking. While generally considered safe, understanding its basic safety profile, including any potential irritant properties, is important for handling. The ammonium citrate CAS number, 3458-72-8, serves as a unique identifier for this compound, facilitating access to detailed safety and regulatory information.

In summary, ammonium citrate's combination of buffering capacity, chelating ability, water solubility, and stable physical form makes it a highly versatile chemical. These properties underpin its widespread adoption in diverse applications, highlighting the importance of understanding its fundamental chemical nature.