Eosin 0.5 %, in ethanol 70 %

Eosin 0.5% in ethanol 70% is a solution containing the synthetic dye eosin (tetrabromofluorescein, molecular formula: C_20H_8Br_4O_5) in a 70% alcohol solution with a concentration of 0.5%. This eosin solution is mainly 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 a 70% alcohol solution has implications for staining kinetics and quality. Compared to other concentrations of alcohol in the eosin solution, a 70% solution allows a good balance between staining kinetics and color intensity. It is not as concentrated as a 90% alcohol solution, which results in slower staining, but also less risk of overstaining. At the same time, it is more concentrated than a 50% alcohol solution, which allows for faster staining and better penetration of the dye into the tissue.

Eosin 0.5% in ethanol 70% is thus a versatile and balanced option for histological and cytological applications. The moderate concentration of alcohol and eosin achieves good staining kinetics, maintains color intensity and sharpness of staining, and allows sufficient differentiation of cellular and extracellular structures.