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Toluidine blue
Introduction
Template:Chembox new Tolonium chloride (INN, also known as toluidine blue O) is a compound used in histology.
Test for lignin
Toluidine blue solution is used in testing for lignin, a complex organic molecule that bonds to cellulose fibres and strengthens and hardens the cell walls in plants. A positive toluidine blue test causes the solution to turn from blue to blue-green. A similar test can be performed with phloroglucinol–HCl solution, which turns red.
Toluidine Blue is often used to identify Mast cells. It is also used to stain proteoglycans and glycosaminoglycans in tissues such as cartilage.