|MadSci Network: Environment & Ecology|
Marie- One approach would be to put an inverted pyrex funnel above the candle and to then vent the smoke through a piece of Tygon tubing attached to the funnel stuck into a glass of deionized or distilled water in which some sodium sulfide had been dissolved. The idea would be to have the soot from the candle ultimately reach the aqueous sodium sulfide solution. If the soot contained lead, it should react with the sulfide ion and form a precipitate which would then make the solution turbid. Another approach would simply be to hold a glass plate above the burning candle such that soot deposits on the glass. The soot could then be brushed into a test tube containing a dilute nitric acid solution. The nitric acid would assure that all of the Pb would go into solution. Then put a drop or two of this solution on one of the test strips. If the drop darkens the test strip, this is indicative of the presence of Pb as shown by the presence of the dark PbS (lead sulfide).
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