A 5% sodium tetraborate or borax solution is an aqueous solution containing 5% sodium tetraborate (Na2B4O7 - 10H2O). Sodium tetraborate, also known as borax, is a white crystalline salt and an important boron compound. In histology and cytology, borax solution is commonly used as a buffer solution to maintain pH within a certain range, typically between 8 and 10.

The use of borax solution in histology includes various applications, such as:

1. Buffer solution:Borax is commonly used as a buffer solution in histological staining protocols. It helps to keep the pH stable during staining for optimal staining results.
2. Solvent: borax solution can serve as a solvent in certain staining protocols to keep dyes such as toluidine blue or azure blue in solution.
3. Staining method:In some staining methods, such as Gomori trichrome staining, borax solution is used as a component of the staining procedure to facilitate binding of dyes to tissue.

The use of 5% borax solution in histology offers advantages such as good pH stability, ease of handling, and inexpensive preparation.