Regardless of whether you find a photographic use for it keep your stock bottle out of the darkroom.
No matter how tightly you think you have stoppered the bottle, it will emit fumes which will build up in the air and eventually destroy anything in your darkroom that comes into contact with it. Best store it in the garage or some place ventilated. Put the lid on tight then put it in a plastic bag and tie a knot.
As for an application for it, I have used it as an etchant to make gobos (pattern stencils) for spotlights used on the stage.
Sheets of roofing flashing are cut into pieces 3 or 4 inches square. They are sprayed with two coats of Krylon spray paint and dried thoroughly, at least an entire day. Best for a couple of days.
The pattern you want for your gobo is traced onto the painted metal then, using an Exacto knife or similar tool, scrape away the paint where you want the negative space (holes) to be.
Drop the pattern into a tray of diluted muriatic acid (half-and-half with clean water) until the exposed metal is eaten away. Observe closely and be on the lookout for the acid creeping under the paint lest you get ragged edges on the finished product.
Remove from the acid, using tongs (chopsticks) and rubber gloves. Neutralize the acid with a solution of baking soda and water then rinse clean with running water.
Use paint thinner or stripper to remove the paint. Rinse away all traces of chemicals or paint or else, when it goes into the hot spotlight, it will burn. (Ask me how I know this!
)
Use a jeweler's file or an Exacto knife to clean up any ragged edges or sharpen the corners then you are ready to go!
Sometimes, when the students at my school are putting on a reprise of a famous play, they like to use that show's logo as a curtain warmer. Using this method, anything you can print on paper and transfer to the stencil can be made into a gobo. Other times, we need a dozen of a certain gobo (like a full-stage foliage breakup pattern) but we only have a budget for one or two. Etching copies out of roofing tin is a good way to cut costs.
I don't know what use muriatic acid would have as an ingredient in developing chemistry but I don't see why it can't be used as an adjunct or alternative method to producing other photograpically oriented things. (e.g. Etching plates or something like that.)
