Nigrosin is used for negative staining of bacteria.
Nigrosin is a mixture of synthetic black dyes made by heating a mixture of nitrobenzene, aniline and aniline
hydrochloride in the presence of a copper or iron catalyst. Nigrosin is used for negative staining of bacteria, as well
as the capsule-containing fungus, Cryptococcus neoformans. The shapes and sizes of the organisms are seen as
colour-free outlines against the dark background. Nigrosin consists of a suspension of fine particles of carbon.
These forms a dark background, against which capsules are clearly seen as a result of displacement of the carbon
particles. An advantage of using this method, rather than regular positive stains like methylene blue or carbol
fuchsin, is that prior fixation by heat or alcohol is not needed, so the organisms are seen in more lifelike shapes.
Reagent /Contents:
| Nigrosin | 10.0 g |
| Formalin | 0.5 mL |
| Distilled water | 100 mL |
Appearance: Blackish Violet coloured solution.
