It's not clear if you are only focused on SCN-, because there's ferrocyanide and sulfuric acid...it is said that Erlenmeyer said (haven't looked it
up) something about quantitative reaction of aq. KSCN with permanganate/sulfuric acid (it's a nice balanced reaction to KCN, water, and sulfates,
theoretically), but I'm unsure of the ease of quantitative recovery of KCN or HCN there. |