Identifying Lead Minerals
- Charcoal Test. Any lead mineral when powdered and mixed with sodium carbonate will yield a metallic globule when the mixture is heated on charcoal in the reducing flame. The globule is bright lead color when hot, but becomes covered with a dull oxide coating on cooling. It is very malleable and can be hammered out into la thin sheet. A coating on the charcoal of lead oxide, PbO, will also form, which varies in color from yellow next to the fused mass to white at a distance. It will lbe best obtained by removing the lead globule to a fresh piece of charcoal and heating it in the oxidizing flame.
- Iodide Tests. When lead minerals are mixed with a mixture of potassium iodide and sulfur and heated on either charcoal or plaster they yield a chrome-yellow coating.
- Acid Tests. Lead minerals as a rule are only slowly at-tackeld by acids. Dilute nitric acid is the best solvent to use. If to a nitric acid solution a few drops of hydrochloric or sulfuric acid are added, white precipitates will form, which are respectively lead chloride, PbCI2, and lead sulfate, PbSO4. The latter is quite insoluble.