Treat this with excess of Bisulphate of sodium, then saturate with sulphuretted hydrogen until metals are thrown down as sulphides.
"Aids to Forensic Medicine and Toxicology"
W. G. Aitchison Robertson
Some are best dyed from a bath containing Bisulphate of soda.
"The Dyeing of Woollen Fabrics"
Franklin Beech
The process, working on these lines, becomes as follows: The wool is first dyed in an acid bath with the addition of Glauber's salt and Bisulphate of soda or sulphuric acid, the goods are then washed with water containing a little ammonia to free them from the acid and afterwards dyed with the direct colour in an alkaline bath.
"The Dyeing of Woollen Fabrics"
Franklin Beech