von Orth's Fluid

Stock von Orth's base
Potassium dichromate   22.4 g
Potassium sulphate 9 g
Distilled water 900 mL
Working von Orth's fluid
Stock von Orth's base   90 mL
Formalin, concentrated 10 mL

Make solution just before use.

Dichromate formalin mixtures such as Orth's fluid are unstable and deteriorate, so they must be made just before use. This is conveniently done by keeping a stock solution and adding formalin to it immediately before the tissue is placed into it. Gray recommends thet fixation be carried out in the dark and that the dichromate be washed out with a dilute formalin solution, also in the dark. Presumably, this is because dichromate can be photosensitive under some circumstances.

Generally, one or two day's fixation for normal slices of tissue should be satisfactory.

Wash well with running tap water or dilute formalin in the dark to remove excess dichromate.


Gray, Peter. (1954)
The Microtomist's Formulary and Guide.
Originally published by:– The Blakiston Co.
Republished by:– Robert E. Krieger Publishing Co.
    Orth, (1896)
    Zietschrift für wissenschaftliche Mikroskopie und für mikroskopische Technik, Leipzig




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