It is a chemical standard designed to maintain a constant and stable pH value under acidic conditions, mainly used for the calibration of pH meters in laboratories, industrial processes, and applications such as hydroponics or quality control. It is commonly formulated with citric acid, salts, and buffering agents that ensure its accuracy within a range of ±0.01–0.02 pH units. It is usually traceable to international standards such as NIST or PTB, with a certificate of analysis that guarantees its reliability. It is available in different formats, such as ready-to-use liquid or sachets, and may include colorants to facilitate identification.