(b) Sulfur
1. Dilute 1 drop of the alkaline solution with 1 mL of water, and add a drop
of sodium nitroprusside; a purple coloration indicates the presence of sulfur.
2. Prepare a fresh solution of sodium plumbite by adding 10% sodium hydroxide
solution to 0.2 mL of 0.1 M lead acetate solution until the precipitate
just dissolves, and add 0.5 mL of the alkaline test solution. A black precipitate
or a colloidal brown suspension indicates the presence of sulfur.