Sulphoindigotic acid, also known as sulfindigotic acid, is a chemical compound widely employed in various industries. It serves as a reactive dye, imparting a rich blue color to fabrics, particularly in the textile industry. Additionally, it finds important applications as a pH indicator, with its hue changing from blue to colorless depending on the acidity of the solution. Synonyms for sulphoindigotic acid include indigo sulphonic acid, indigo carmine, and indigo blue. These alternative names refer to different forms or derivatives of the compound, highlighting its versatility and significance across different fields. Whether it's dyeing clothes, indicating pH levels, or conducting scientific experiments, sulphoindigotic acid remains a valuable compound with various synonyms in the scientific community.