Yes, I was aware that picric acid has fabric dye applications. But what would hundred year old jars of it be doing in a primitive photo darkroom? Could someone have been experimenting with some color photography invention using it?
As for seeming over-reaction by the hazmat team, keep in mind that in this area multiple houses have burned down all at once due to exploding naughty artiste chemicals, including ether used in certain alt photo techniques (as well as meth labs). In this case, the basement darkroom was in a rather spiffy neighborhood of very expensive older homes. I once photographed the gardens one of those, and much earlier actually lived in one in exchange for restoration work - a lovely Julia Morgan classic home; she was America's finest woman architect ever, who was also behind Hearst Castle. Those kinds of houses simply cannot be replaced; and the twisty streets are hard to evacuate in an emergency.