Eosin 2%, alcoholic 70% with 0.5% acetic acid, is an eosin solution used in histology and cytology for selective staining of basic structures such as proteins, especially cytoplasm and extracellular matrix. The solution consists of a concentration of 2% eosin, 70% alcohol and 0.5% acetic acid, making it suitable for various applications where moderate staining is desired.

The alcohol content in this solution acts as a solvent and allows faster diffusion of the dye into the tissue, resulting in a shorter staining time. The faster diffusion of the alcoholic solution allows for better penetration of the dye into the tissue and more even distribution of the dye. In addition, the alcohol content helps reduce cell swelling, resulting in sharper visualization of structures.

The acetic acid in the solution affects the pH of the staining solution, increasing the binding affinity of eosin to the basic structures in the tissue. This results in more intense and sharper staining of the structures examined. The addition of acetic acid can also help reduce nonspecific background staining and improve the contrast quality of the stained specimen.

The 2% eosin concentration in this solution provides a balanced staining that is well suited for the detection of cellular and extracellular structures in histological sections. The intensity of the staining can be further optimized by adjusting the exposure time and concentration of eosin. The alcoholic eosin solution with acetic acid is suitable for routine staining as well as for special staining techniques where stronger staining is desired.