Hydrochloric acid alcohol (0.3% / 70%) has similar properties and applications to the 1% / 70% version, but with a lower concentration of hydrochloric acid. This is used in histology and microscopy, where it is also used for decolorization and differentiation.

In staining protocols such as Ziehl-Neelsen staining, hydrochloric acid alcohol (0.3 % / 70 %) is used as a decolorizer. Here, it removes excess dye from non-specifically bound areas, allowing clearer visualization.

However, the lower hydrochloric acid concentration gives this solution a difference in application. With only 0.3% hydrochloric acid, it has a milder effect than the 1% / 70% version and therefore could be less aggressive on sensitive tissue samples. However, it remains effective in decolorizing and differentiating stains.