In the early days of photography, a wide range of developing agents were used, including chlorohydroquinone, ferrous oxalate,[REF]:131 hydroxylamine, ferrous lactate, ferrous citrate, Eikonogen, atchecin, antipyrin, acetanilid and Amidol (which unusually required mildly acidic conditions).
The original lithographic developer was based upon a low sulfite/bisulfite developer with formaldehyde(added as the powder paraformaldehyde).