Disambiguation:
This page decribes a holographic recording material that is a gelatin layer made light sensitive by the introduction of one the dichromate family of chemicals, described here. A type of stock image hologram produced using this process, that was most popular in the late 1970's and early 1980's, which was affectionately termed "A Dichromate" in the trade, is described here.
There are 2 chromates in the molecule, hence dichromate, the prefix di- meaning 2; sometimes this family is called bichromate, with the prefix bi-also meaning 2. Photographers are the ones that usually call them that, hearkening back to their nomenclature of gum bichromate. Chromate is
Chromate salts contain the chromate anion, CrO2−
4. Dichromate salts contain the dichromate anion, Cr
2O2−
7.
The most likely dichromates to be found in a holographer's chemical storage are ammonium and potassium dichromate. They can be used to make