• A blue color is indicative of copper. • Any bismuth will precipitate as Bi(OH) 3 . • Centrifuge and decant, saving both precipitate and decantate. 7. Identification of Copper and Bismuth • Add several drops of 0.3M K 4 [Fe(CN) 6 ] to the decantate from Step 6. • A pink ‐ to ‐ red precipitate of Cu 2 [Fe(CN) 6 ] confirms the presence of copper. • Add 4 drops of 3M NaOH and 1 drop of 0.5M SnCl 2 to the precipitate from Step 6. • The formation of a black residue of metallic bismuth confirms the presence of bismuth. Bismuth hydroxide 8. Analysis of Subgroup IIB; Identification of Antimony • To the solution from Step 3 (labeled Group IIB) add 10 drops of 12M HCl and heat in a water bath for about 2 minutes (some precipitation of Sb 2 S 3 may be observed at this point). • Add 10 more drops of 12M HCl and boil gently until all the H 2 S has been expelled, about 5 minutes. • Any precipitate formed from the first addition should now redissolve. • If a yellow (sulfur) residue remains , centrifuge and discard the precipitate. • Add 5 mL of water to this solution, and then add 10 drops of thioacetamide and heat in a water bath for a few minutes. • Formation of an orange precipitate of Sb 2 S 3 confirms the presence of antimony. Positive Sb test Positive Bi test Actual photos from lab
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- Fall '09
- drops, Group II Cations