Early American photography manuals often include Acetic acid, No.8, in their formulas.

I have found two 19th. century references to its strength.

One from a formula given by Charles W. Hull, “New York Correspondence,” Philadelphia Photographer, 1869, this states that 32 drachms of No.8 are equivalent to 4 drachms of Glacial Acetic acid. i.e. No.8 is one eighth of the strength of Glacial Acetic.

However, Waldack and Neff in their ‘Treatise Of Photography On Collodion’, 1858, page 89 state: "The acetic acid known as No.8 is generally used in its place. It contains 25 to 35 per cent.pure acid".

i.e. No.8 is one quarter to one third of the strength of Glacial Acetic acid.

I have been using the one eighth dilution quite successfully in my interpretation of Carey Lea's recipes.

Does anyone know of other references to No.8's strength?

28% It what is known as 'stop bath'

Some have said the no 8 refers to 8 baume but that is 50% acetic acid.