Introduction & Profiles

Aim:

• To find out the strength in the degreasing tank

Apparatus Required:

• 25 ml graduated pipette 1nos, 2m1 pipette 1nos, Conical flask 2nos and White tile

Reagents:

• M ethyl orange indicator, Phenolphthalein indicator, N/10 Sulphuric acid

Procedure:

Total Alkali:

• Firstly clean all apparatus with weak acid and then with water and again with distilled water
• Take 2m1 from the bath and drain into a conical flask to the last drop. Add 10 drops of methyl orange indicator with constant stirring, care must be taken that the indicator does not fall on the inner walls of the flask. The color of the solution will immediately turn orange
• Now take N/10 Sulphuric acid in a 25ml pipette and titrated, by adding it drop by drop into the conical flask. Keep titrating till the orange color turns into pink color
• When the solution in the conical flask turns pink, stop the titration and note the ml consumed inside the pipette, this is your Total Alkali

Free Alkali:

• Firstly clean all apparatus with weak acid and then with water and again with distilled water
• Take 2m1 from the bath and drain into a conical flask to the last drop. Add 10 drops of Phenolphthalein indicator with constant stirring, care must be taken that the indicator does not fall on the inner walls of the flask. The color of the solution will immediately turn Pink
• Now take N/10 Sulphuric acid in a 25m1 pipette and titrated, by adding it drop by drop into the conical flask. Keep titrating till the disappearance of pink color or pale pink
• When the solution in the conical flask turns Pale pink to colorless, stop the titration and note the ml consumed inside the pipette, this is your Free Alkali

Formula:

• Total Alkali / Free Alkali  = 1.4- 1.8

 

Aim:

• To find out the Strength in the Phosphating tank

Apparatus Required:

• 25 ml graduated pipette 1nos, 10ml pipette 1nos, 2ml pipette 1 nos, Conical flask 2nos, White tile

Reagents:

• Phenolphthalein indicator, Bromocresol green indicator, N/10 (0.1N) Sodium hydroxide

Procedure:

Total acid:

• Firstly clean all apparatus with weak alkali and then with water and again with distilled water
• Take 5ml from the bath and drain into a conical flask to the last drop. Add 10 drops of Phenolphthalein indicator with constant stirring, care must be taken that the indicator does not fall on the inner walls of the flask. There shall be no significant change in the colour
• Now take N/10 Sodium hydroxide in a 25ml pipette and titrate, by adding it drop by drop into the conical flask. Keep titrating till the solution turns into pale permanent pink colour that shall be visible for atleast 20 seconds. When the solution in the conical flask turns pale pink, stop the titration and note the ml consumed inside the pipette, this is your Total Acid

Free acid:

• Firstly clean all apparatus with weak alkali and then with water and again with distilled water
• Take 10ml from the bath and drain into a conical flask to the last drop. Add 10 drops of Bromocresol green indicator with constant stirring, care must be taken than the indicator does not fall on the inner walls of the flask. The color of the solution will immediately turn yellow
• Now take N/10 Sodium hydroxide in a 2ml pipette and titrate, by adding it drop by drop into the conical flask. Keep titrating till the yellow color turns just green
• When the solution in the conical flask turns just green, stop the titration and note the ml consumed inside the pipette, this is your Free Acid

Legend Total acid:

• 14-18 Free acid 1.5-2

Check if the Total Acid and Free Acid are correct in the phosphating tank. Dip a strip of starch iodide paper in the bath, and take out immediately. Now observe the color change instantly. If the color changes to color of starch iodide paper.

• White - No accelerator
• Pale mauve - Insufficient accelerator
• Blue - Correct accelerator
• Blue black - Excess accelerator