Potassium metabisulphite 0.5 % consists of 1000 ml distilled aqua. / deionized water and 5 g potassium disulphite. This chemical mixture is frequently used in medical diagnostics, in histology and in scientific laboratories, where it is mainly used in staining kits, such as the etchant according to Lichtenegger and Bloech. The product plays a crucial role in the preparation of microscopic specimens by enabling clear visualization of tissue structures. Chemically, water (H₂O) is the solvent and potassium metabisulfite (K₂S₂O₅), also known as potassium disulfite, is the active ingredient. K₂S₂O₅ acts as a reducing and bleaching agent, whereby it splits off oxygen under the influence of light and heat and reacts to form potassium sulphate (K₂SO₄) and sulphur dioxide (SO₂). This reaction helps to stabilize the sample by preventing oxidative processes and fixing the structure of the tissues. The results resulting from this application include improved staining contrasts and increased detail in histological sections, which is important for correct diagnosis and research studies. Uses in medical diagnostics and research.