Redry and grind sample. If you want C and N measurements on the same sample, send a separate bottle with unleached sample. If no precipitate forms, raise the pH to 5 or 6 with NaOH additions, and repeat procedure. Sulfides dissolved in water . Let solution stand overnight at room temperature, siphon off supernatant.
Solid phase sulfides.
Sulfides in minerals and sediments are often separated from surrounding rock or organic matrix by chromium reduction and acid distillation. Treat the zinc sulfides from traps as described above for sulfides dissolved in water. Concentrate silver sulfides by filtration and scrape from filter. Label distinctly, provide accompanying data sheet with sample number, description, and your name and telephone number. A short description of your project and goals would be helpful, but is not necessary.