Eosin 1% alcoholic 70%, acetic acid 0.5% is a solution containing the synthetic dye eosin (tetrabromofluorescein, molecular formula: C_20H_8Br_4O_5) at a 1% concentration, dissolved in 70% ethanol and 0.5% acetic acid. This eosin solution is widely used in histology and cytology to stain cell structures and the extracellular matrix. Eosin has a high affinity for basic structures such as proteins and typically stains them pink or red.

The use of 70% ethanol has several advantages, as it allows for faster staining while providing better fixation of cells during the staining process. The addition of 0.5% acetic acid in the solution has two main functions. First, it allows better diffusion of the dye into the tissue, resulting in more uniform staining. Second, the acetic acid promotes the decolorization of excess eosin, resulting in improved differentiation of cellular and extracellular structures.

Eosin 1% alcoholic 70%, acetic acid 0.5% is therefore a good choice for histological and cytological applications where rapid and uniform staining and improved differentiation of cellular and extracellular structures are important. The use of ethanol and acetic acid provides optimal staining that preserves the morphological characteristics of cells and tissues and allows adequate differentiation of cellular and extracellular structures.