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Alloy Analysis (Brass)
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Materials Required:

 

  1. Electronic balance
  2. 250 mL beaker
  3. Conical flask
  4. Watch glass
  5. Desiccator
  6. Sintered and silica crucible
  7. Funnel
  8. Whatman filter paper
  9. Bunsen burner
  10. Electric burner
  11. Kipp's apparatus
  12. Butter paper
  13. Tissue paper
  14. Tongs
  15. Tile
  16. Oven

 

Reagents :

 

  1. Brass powder
  2. conc. HNO3
  3. 10 N HNO3
  4. dil. HNO3
  5. conc. H2SO4
  6. 1% H2SO4
  7. conc. HCl
  8. dil. HCl
  9. 10% ammonium thiocyanate
  10. NH3
  11. NH4Cl
  12. 10% ammonium hydrogen phosphate
  13. Distilled water

 

Procedure:

 

Estimation of Tin

 

  1. Weigh accurately about 1.0000 g of Brass powder
  2. Transfer brass into 250 mL beaker
  3. To that add 15 mL of 10 N HNO3 using measuring jar.
  4. The precipitate (stannic acid ) will form, and keep it for settling. After settling the precipitate ensure the complete precipitation of all stannic acid by adding two drops of dil. HNO3 along the side of the beaker)   and it was evaporated on a water bath nearly to dryness
  5. Taken out from the water bath.
  6. Dilute with 50 mL water, stirred using glass rod and heat for 25 min
  7. Add some paper pulp (1 or 2) and stirred using glass rod
  8. Taken out from the burner and allow to cool
  9. Filter through whatmann filter paper and wash the precipitate with dil. HNO3
  10. Take silica crucible from desiccator and weighed
  11. Transfer the precipitate with filter paper into weighed silica crucible
  12. Ignite the precipitate at 900-1000 oC up to getting constant weight of SnO2 (Tin dioxide)
  13. Taken out from the electric burner and cool it and keep it in desiccator (5 min) using tongs.
  14. Taken out from the desiccator and weighed

 

Estimation of Lead

 

  1. Concentrate the above filtrate to 50 mL
  2. Cool and add conc. H2SO4  and evaporate the solution until fumes evolved 
  3. Cool it and dilute to 100 mL using distilled water and again heat the solution
  4. Filter through a previously weighed sintered crucible
  5. Washed the above obtained precipitate with 1% H2SO4
  6. Dried at 130 oC and weighed it as PbSO4 (Lead(II) sulfate)

 

Estimation of Copper

 

  1. Evaporate the filtrate (obtained above after complete separation of Lead) to 50 mL
  2. Add 5 mL dil. HCl and diluted to 100 mL using water
  3. Add 3 g sodium thiosulfate to the solution
  4. Heated to boiling and added 10 mL 10% ammonium thiocyanate
  5. Boiled and filtered through a previously weighed sintered crucible
  6. Washed with water and dried and weighed as CuSCN (copper(I)thiocyanate)

 

Estimation of Iron

 

  1. To the filtrate obtained after the complete separation of copper add 35 mL conc. HNO3 and 15 mL conc. HCl
  2. Evaporate to dryness and the add 3-5 mL of conc. HCl
  3. Warm it and dilute to 50-75 mL water and heated to boiling.
  4. To the boiling solution, add ammonium hydroxide solution carefully with constant stirring untill a faint,but distinct, smell of ammonia persists over the solution.
  5. Boil further for 2-3 minutes.
  6. Precipitate iron as Fe(OH)3 iron(III) hydroxide)
  7. Filter it through Whatmann filter paper and ignite on previously weighed silica crucible
  8. Cool and weighed

 

Estimation of Zinc

 

  1. To the final filtrate add 10 mL conc. HCl
  2. Heat the filtrate
  3. Taken out and pass H2S  using Kipp's apparatus
  4. Filter and  wash with water)
  5. Collect the filtrate (discard the precipitate)and boil off H2S
  6. Taken out and add 3 g NH4Cl and conc. HNOboil and add NH3
  7. Again boil and filter using filter paper
  8. Collect the filtrate
  9. Add methyl red and 5 mL conc. HCl
  10. Neutralize with 5 mL NH3
  11. Add 15 mL 10% ammonium hydrogen phosphate
  12. Filter, wash with water ignite on previously weighed silica crucible and weighed as Zn2P2O7 (Zinc Pyrophosphate)

 

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

 

  1. Always wear lab coat and gloves when you are in the lab. When you enter the lab, switch on the exhaust fan and make sure that all the chemicals and reagents required for the experiment are available. If it is not available, prepare the reagents using the components for reagent preparation.
  2. Properly adjust the flame of the Bunsen burner. The proper flame is a small blue cone; it is not a large plume, nor is it orange.
  3. Make sure to clean all your working apparatus with chromic acid and distilled water and ensure that all the apparatus are free from water droplets while performing the experiment.
  4. Make sure to calibrate the electronic weigh balance before taking the measurements.
  5. Ensure that the desiccator  has sufficient amount of desiccant; Silica gel
  6. Use chromic acid to clean the crucible, then heat it and make sure to cool it and before placing in the desiccators. Ensure that you are handling the crucible, with cleaned tongs or with tissue paper .Never touch it with your hand.
  7. Switch on the oven and adjust the temperature to 1300 C. Make sure to use a cotton glove while working with a hot air oven.
  8. Make sure to clean the Kipp's apparatus tube with water and ensure that it has sufficient solid material; iron sulfinide and acid, H2SO4 for producing H2S gas.
  9. Clean all glass wares with soap and distilled water. Once the experiment completed recap the reagent bottles. Switch off the light, exhaust fan, hot air oven and Gas cylinder before leaving the lab.
  10. Discard the used gloves in a waste bin.

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