Tools

Alloy Analysis (Brass)

Materials Required:

  • Electronic balance
  • 250 mL beaker
  • Conical flask
  • Watch glass
  • Desiccator
  • Sintered and silica crucible
  • Funnel
  • Whatman filter paper
  • Bunsen burner
  • Electric burner
  • Kipp's apparatus
  • Butter paper
  • Tissue paper
  • Tongs
  • Tile
  • Oven

Reagents :

  • Brass powder
  • conc. HNO₃
  • 10 N HNO₃
  • dil. HNO₃
  • conc. H₂SO₄
  • 1% H₂SO₄
  • conc. HCl
  • dil. HCl
  • 10% ammonium thiocyanate
  • NH₃
  • NH₄Cl
  • 10% ammonium hydrogen phosphate
  • Distilled water

Procedure:

Estimation of Tin

  1. Weigh accurately about 1.0000 g of Brass powder
  2. Transfer brass into 250 mL beaker
  3. Add 15 mL of 10 N HNO₃ using measuring jar
  4. Wait for stannic acid precipitate to form, let it settle
  5. Add 2 drops of dil. HNO₃ along the side of the beaker
  6. Evaporate on a water bath nearly to dryness
  7. Take out from the water bath
  8. Dilute with 50 mL water, stir and heat for 25 min
  9. Add 1–2 paper pulps and stir
  10. Cool and filter through Whatman filter paper, wash with dil. HNO₃
  11. Weigh a silica crucible from desiccator
  12. Transfer precipitate with paper into the crucible
  13. Ignite at 900–1000°C to get constant weight of SnO₂
  14. Cool, place in desiccator for 5 minutes, then weigh

Estimation of Lead

  1. Concentrate above filtrate to 50 mL
  2. Cool and add conc. H₂SO₄, evaporate until fumes evolve
  3. Cool, dilute to 100 mL, and heat again
  4. Filter through pre-weighed sintered crucible
  5. Wash precipitate with 1% H₂SO₄
  6. Dry at 130°C and weigh as PbSO₄

Estimation of Copper

  1. Evaporate filtrate to 50 mL
  2. Add 5 mL dil. HCl, dilute to 100 mL
  3. Add 3 g sodium thiosulfate
  4. Boil and add 10 mL 10% ammonium thiocyanate
  5. Boil and filter through weighed sintered crucible
  6. Wash, dry, and weigh as CuSCN

Estimation of Iron

  1. Add 35 mL conc. HNO₃ and 15 mL conc. HCl to filtrate
  2. Evaporate to dryness, then add 3–5 mL conc. HCl
  3. Warm and dilute to 50–75 mL, boil
  4. Add NH₄OH with stirring until faint ammonia smell persists
  5. Boil 2–3 min to precipitate Fe(OH)₃
  6. Filter, ignite in weighed crucible, cool and weigh

Estimation of Zinc

  1. Add 10 mL conc. HCl to final filtrate and heat
  2. Pass H₂S gas using Kipp’s apparatus, filter and discard precipitate
  3. Boil filtrate to remove H₂S
  4. Add 3 g NH₄Cl and conc. HNO₃, boil and add NH₃
  5. Boil, filter, and collect filtrate
  6. Add methyl red and 5 mL conc. HCl, then neutralize with 5 mL NH₃
  7. Add 15 mL 10% ammonium hydrogen phosphate
  8. Filter, wash, ignite in weighed crucible and weigh as Zn₂P₂O₇

Points to Remember while Performing the Experiment in a Real Laboratory:

  • Always wear lab coat and gloves
  • Turn on exhaust fan and check reagent availability
  • Use a proper Bunsen flame (small blue cone)
  • Clean all apparatus with chromic acid and distilled water
  • Calibrate the electronic balance before use
  • Ensure desiccator has sufficient silica gel
  • Clean crucible with chromic acid, heat, cool, and use tongs/tissue
  • Set oven to 130°C and wear cotton gloves
  • Clean Kipp's apparatus, ensure enough iron sulfide and acid
  • Recap reagents, turn off gas, oven, lights before leaving lab
  • Discard used gloves in a waste bin