Congo Red stock solution, also known as Congo Red, is a concentrated solution of the azo-based dye used in biological and medical research for professional users. The characteristic application of Congo Red is in its ability to identify amyloid deposits in tissue preparations that occur in various diseases such as Alzheimer's and other neurodegenerative disorders.

Congo Red dye has a high affinity for amyloid structures and can make them appear red-birefringent under polarized light. This enables precise identification and localization of these deposits, which is critical for the diagnosis and study of amyloid-associated diseases.

The stock solution serves as a starting solution for the preparation of diluted, ready-to-use staining solutions that can be customized according to the desired intensity and application. When using Congo Red stock solution, it is important to select the correct dilution and staining parameters for the particular preparation and staining method chosen to ensure clear, differentiated visualization of amyloid structures.

In addition, Congo Red can be used as a pH indicator as it changes color depending on the pH of the medium. At lower pH values it appears red, while at higher pH values it is blue. It is commonly used in laboratory settings to quickly determine the pH of a solution. The concentrated Congo Red stock solution provides users with flexibility and efficiency in adjusting the dye concentration, allowing optimal use of the dye.