Ferric Chloride 32% is a concentrated aqueous solution of ferric chloride (FeCl3) that is commonly used as a stock solution to prepare dilute solutions for various applications, including histology.

In histology, ferric chloride is commonly used to stain tissue specimens by diluting it from the stock solution to the required concentration. In particular, it is used for the Perls reaction, in which it is used to identify hemosiderin in tissue specimens, an iron-containing pigment that acts as an indicator of iron overload and hemochromatosis.
To prepare the desired working solution for the Perls reaction or other histological procedures, the 32% iron(III) chloride solution is diluted according to the requirements of the particular method. Dilution is important to achieve optimal staining results and to reduce the corrosiveness of the solution.

Iron(III) chloride 32% is not only widely used in histology, but also finds application in metallography and etching of printed circuit boards.
In metallography, iron(III) chloride is used to etch metals and alloys to reveal their microstructures. By treating the surface with iron(III) chloride, different phases and structures within the material are selectively attacked and thus highlighted. This allows the quality of the metal or alloy to be assessed and material properties such as grain boundaries, phase boundaries or inclusions to be investigated.

When etching printed circuit boards, iron(III) chloride is used as an etchant to remove unwanted copper from the surface of the board. In this process, the PCB is first coated with a light-sensitive layer (photoresist) and then subjected to a photolithography process in which the desired circuit pattern is exposed. The exposed areas of the photoresist cure and protect the underlying copper, while the unexposed areas can be removed. The circuit board is then immersed in a solution of dilute ferric chloride, which selectively dissolves the exposed copper, leaving the desired pattern on the circuit board.