Smith & McNulty zirconyl hematoxylin is a solution used in medical diagnostics, histology and scientific laboratories. It is mainly used for the detection of acidic mucins, and it can replace Alcian blue at a pH of 2.5.

The solution consists of several ingredients: distilled water, anhydrous glycerol, ethanol, sodium iodate, hematoxylin and zirconyl chloride octahydrate. Zirconyl chloride octahydrate (ZrOCl₂-8H₂O) is a water-soluble derivative of zirconium and is a major component of this solution. Hematoxylin, a natural dye molecule, is converted to its active form, hematoxylin, by sodium iodate. When combined with zirconyl chloride octahydrate, it forms strongly colored complexes that provide intense staining.

Application of this solution results in specific staining: Cell nuclei are stained green and acid mucins are stained purple. The intensity of the staining can be controlled by the duration of contact of the tissues with the solution, and excess staining can be removed with a solution of dilute ethanol and hydrochloric acid.