Müller's colloidal iron solution, consisting of finely dispersed iron(III) chloride in water, has numerous applications in life sciences and medical diagnostics. One of its most prominent applications is in histology, where it is used to stain specific cell structures, particularly mucin.

The high specific affinity of iron ions for these substances allows precise and effective visualization of cell structures that would otherwise be difficult to detect. This special aptitude makes it an indispensable tool in microscopy and for the examination of tissue samples.

Chemically, the solution is iron(III) chloride, which is finely distributed in the solution due to its high solubility in water. This colloidal nature ensures a uniform and effective reaction with other substances.

When used as a reagent, the solution binds to specific biochemical compounds, allowing direct visualization or characterization. In medical diagnostics, for example, it is used to visualize mucin structures in tissue samples, allowing disease processes to be better understood and diagnosed.