[There were also recipes in the 70s that used it as a coloring agent in making salt/sugar crystals.]
I remember it as being (something) Blue - "Prussian" sounds right. It used to be used as an antibiotic sort of thing. It came in a small bottle; in liquid form. Itd stain your fingers purple for a week or more.
Our horses would scrape their leg on the fence and wed have to drain the infected wound, give an antibiotic shot and dress the wound with the purple liquid. I thought it was Prussian Blue. I could be wrong
I know its a dumb question, I'm just trying to figure out if it's the same stuff I saw as a kid... it's interesting to see the various uses of different things.
BTW...Blu-Kote is reported to be one of the few OTC items that will 'kill off' tetnus 'germies'.