I'm a book and paper conservator, and a few years ago had four books to restore. Their endpapers were this gorgeous green silk, but they were badly dry rotted, and needed to be removed. I suspected the fabric of having the dye Scheele's Green (copper hydrogen arsenite), and tried to see if my local university would test it for me, but they stopped communicating. I'd like to confirm or refute these steps, so that I can close out this project, and let the customer (a large library) know if their collections house/housed fabric dyed with Scheele's Green.
From the Scientific American, 5 Feb 1881:
EASY TEST FOR ARSENIC IN FABRICS Immerse the suspected paper in strong ammonia on a white plate or saucer; if the ammonia becomes blue, the presence of a salt of copper is proved; then drop a crystal of nitrate of silver into the blue liquid, and if any arsenic be present, the crystal will become coated with yellow arseniate (sic) of silver, which will disappear on stirring.
This is the extent of instruction provided. It makes sense for it to have been published like this, as this was the period in which much of the Scheele's Green cleanup happened (it was everywhere, but once they understood what was killing people, they tried to rid their houses of it. It was most notoriously used in clothing and wallpaper).
Can anyone confirm these steps? Is it safe (with PPE)? Is there an easier method? I know silver nitrate is caustic, but aside from those handling concerns? And would Ammonia at the common household dilution do the job?