It can therefore be used to selectively stain mitotic cells (where the nuclear membrane has dissolved) with antibodies against chromatin[1] Zenker's fixative contains mercuric chloride ("corrosive sublimate"), potassium dichromate, sodium sulfate, water, and acetic acid.
Fixatives containing mercuric chloride or potassium dichromate are toxic, making disposal as hazardous waste costly.
Zenker is usually made with 50g of mercuric chloride, 25g of potassium dichromate, 10g of sodium sulfate (decahydrate) and distilled water to complete 1000 ml.
If the glacial acetic acid is replaced by 5 ml of formalin (37–40% formaldehyde), the resulting solution is Helly's fixative, also sometimes called "formol-Zenker".
Helly is stable for only a few hours because the formaldehyde and dichromate components react, producing formic acid and chromium(III) ions; the orange solution becomes greenish.