Thank you for your response. That is the only info about vitriolic acid I have ever been able to find either. I keep thinking there must have been some other household use for it. Not everyone would be doing their own hide tanning, especially in a city/town and the volumes required don't mesh with widespread use and the smaller apothecary type jars of the time. I don't know if the vitriolic acid just had some sort of symbolism in the movie I referred to. Just one of those things...thought I would ask it here. Thank you for your response.