Friday, December 31, 2021

Assay of sodium bicarbonate

Learn about the assay of sodium bicarbonate through a laboratory experiment or practical.

Aim:

To determine the percentage purity (assay) of sodium bicarbonate in a given sample using standard 1 N HCl.

Reference: USP Pharmacopoeia, USP31–NF26 Page 3240

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.

Chemicals: Sodium bicarbonate (NaHCO3), methyl red TS, and hydrochloric acid (HCL), etc.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
  • Take 03.00 gm of sodium bicarbonate and pour it into a conical flask, and mix with 100 ml of water.
  • Then, as an indicator, add 2-3 drops of methyl red TS and properly mix it.
  • Titrate the sample solution with standardized 1 N hydrochloric acid until the endpoint is reached.
  • Add the HCl slowly, with constant stirring, until the solution becomes faintly pink.
  • Bring the solution to a boil, then cool and repeat the titration until the faint pink color no longer fades after boiling.
  • Properly record the readings of the burette.
  • To get accurate results, repeat the titration three times.
  • Take their mean and calculate the percentage purity of sodium bicarbonate.
  • Each mL of 1 N hydrochloric acid is equivalent to 84.01 mg of NaHCO3.

Observation table:

Sr. No.

Content in conical flask

Burette reading

Volume of titrant used (ml)

Initial

Final

1

 

 

 

 

2

 

 

 

3

 

 

 

 

Mean:
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Assay of magnesium sulphate

Learn about the assay of magnesium sulphate through a laboratory experiment or practical.

Aim:

To determine the percentage purity of magnesium sulphate using standard 0.1 N EDTA (Direct titration).

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.

Chemicals: Magnesium sulphate heptahydrate (MgSO4), disodium edetate (EDTA), ammonia (NH3), calcium chloride (CaCl2), ammonium chloride (NH4Cl), and solochrome black-T indicator or mordant black II, etc.

Reaction Involved:

The assay of MgSO4.7H2O is based upon the reactions designated by the following equations:
Mg2+ + [H2X]2‑→ [MgX]‑ + 2H+

Preparation and standardization of 0.05 M EDTA solution:
Click here to get the procedure.

Preparation of strong ammonia-ammonium chloride solution:
Click here to get the procedure.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
  • Take 0.3 gm of magnesium sulphate and pour it into a conical flask, and dissolve in 50 ml of warm water.
  • Using a pipette, add 10.00 ml of strong ammonia-ammonium chloride solution.
  • Then, as an indicator, add 2-3 drops of mordant black II mixture and properly mix it.
  • Titrate the sample solution with standardized 0.05 disodium edetate until the endpoint is reached.
  • The actual endpoint is indicates by the pink color is discharged from the blue.
  • Properly record the readings of the burette.
  • To get accurate results, repeat the titration three times.
  • Take their mean and calculate the percentage purity of magnesium sulphate.
  • Each ml of 0.05 M disodium ethylene diamine tetracetate is equivalent to 0.00602 g of MgSO4.

Observation table:

Sr. No.

Content in conical flask

Burette reading

Volume of titrant used (ml)

Initial

Final

1

 

 

 

 

2

 

 

 

3

 

 

 

 

Mean:

Result:

The percentage purity of the magnesium sulphate (MgSO4) sample was found to be_____.


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Thursday, December 30, 2021

Assay of calcium carbonate

Learn about the assay of calcium carbonate through a laboratory experiment or practical.

Aim:

To determine the percentage purity of calcium carbonate using standard 0.1 N EDTA (Direct titration).

Reference: Indian Pharmacopeia (IP)

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.

Chemicals: Calcium carbonate (CaCO3), hydrochloric acid (HCl), disodium edetate (EDTA), and calcon indicator mixture, etc.
Preparation of dilute hydrochloric acid:

Preparation of 0.05 M EDTA solution:

Click here to get the procedure.

Preparation of sodium hydroxide solution:

Take properly weighed 10.00 gm of oxalic acid and dissolve in 50 ml of distilled water in a volumetric flask, and properly mix it. Once it has completely dissolved, make up the volume to 100 ml.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
  • Take properly weighed 01.00 gm of calcium carbonate and dissolved in 10.00 ml water and 03.00 ml dilute hydrochloric acid.
  • Boil for 10 minutes, then cool and dilute with water to 50.00 ml.
  • Titrate with 0.05 M EDTA to within a few ml of the predicted end-point, then add 08.00 ml of NaOH solution and 100 mg of calcon mixture as an indicator, and keep titrating until the color of the solution changes from pink to a blue.
  • To get accurate results, repeat the titration three times.
  • Properly record the readings of the burette.
  • Take their mean and calculate the % purity of calcium carbonate.

Observation table:

Sr. No.

Content in conical flask

Burette reading

Volume of titrant used (ml)

Initial

Final

1

 

 

 

 

2

 

 

 

3

 

 

 

 

Mean:

Calculation:

Each ml of 0.05M EDTA is equivalent to 0.005004 g of calcium carbonate.

% Assay = V x M x F / 0.05 x W x 100 / (100-LOD)

Where,
V is blank reading- sample reading
M is the molarity of 0.05M disodium Edetate
F is factor
W is the sample weight

Result:

The percentage purity of the calcium carbonate (CaCO3) sample was found to be_____.
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Assay of boric acid

Learn about the assay of boric acid through a laboratory experiment or practical.

Aim:

To determine the percentage purity (assay) of boric acid in a given sample using standard 0.1 N NaOH.

Reference: Indian Pharmacopeia (IP)

Principle of assay of boric acid:

The alkalimetry method is used to perform an assay of boric acid. Since it is such a weak acid, it cannot be accurately titrated with a strong base. It behaves like a strong monobasic acid when dissolved in a mixture of water and glycerol, and it may then be titrated with a standard alkali solution using phenolphthalein as an indicator.

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.

Chemicals: Boric acid (H3BO3), glycerol (C3H8O), phenolphthalein indicator, sodium hydroxide (NaOH), and oxalic acid (C2H2O4), etc.

Preparation of 1N NaOH solution:

Take properly weighed 04.00 gm of sodium hydroxide and dissolve in 50 ml of distilled water in a volumetric flask, and properly mix it. Once it has completely dissolved, make up the volume to 100 ml.

Preparation of 1N oxalic acid solution:

Take properly weighed 06.30 gm of oxalic acid and dissolve in 50 ml of distilled water in a volumetric flask, and properly mix it. Once it has completely dissolved, make up the volume to 100 ml.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
For standardization of sodium hydroxide:
  • Pipette out 10.00 ml of 0.1 N oxalic acid into a conical flask and add 1-2 drops of phenolphthalein indicator.
  • Titrate the solution against the NaOH solution until it turns pink in color.
  • Repeat the titration to get concurrent values.
For assay:
  • Take properly weighed 02.00 gm and dissolved in 50.00 ml water and 100 ml glycerol solution previously neutralized to phenolphthalein solution.
  • Add 2-3 drops of phenolphthalein indicator.
  • Titrate the sample solution with 1N NaOH until the endpoint is reached.
  • The actual endpoint of the titration is indicated by a faint pink color.
  • Properly record the readings of the burette.
  • To get accurate results, repeat the titration three times.
  • Take their mean and calculate the % purity of boric acid.

Observation table:

Sr. No.

Content in conical flask

Burette reading

Volume of titrant used (ml)

Initial

Final

1

 

 

 

 

2

 

 

 

3

 

 

 

 

Mean:

Calculation:

I.P. factor: Each ml of 1 N NaOH is equivalent to 0.016183 g of H3BO3.

Formula:
Percent purity of H3BO3= Volume of NaOH x I.P. Factor x 100 x N of NaOH (actual) / weight of H3BO3 x N of NaOH (exp)

Result:

The percentage purity of the boric acid (H3BO3) sample was found to be_____.



Frequently Asked Questions (FAQ):

Why Glycerin is used in the assay of boric acid?

Glycerin is used in the assay of boric acid because boric acid is a weak monobasic acid that does not easily react with sodium hydroxide because of its low tendency to give hydrogen ions in its solution. When glycerol and boric acid are combined, the boric acid becomes more acidic and can readily act as a monobasic acid.

Assay of boric acid is done by which titration?

The assay of boric acid is performed using acid-base titration (alkalimetry), in which acidic substance-using a standard base.


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Wednesday, December 29, 2021

Preparation and standardization of 0.1 M potassium hydroxide

Learn about the preparation and standardization of 0.1 M potassium hydroxide solution through a laboratory experiment or practical.

Aim:

To prepare and standardize 0.1 M potassium hydroxide solution using HCl.

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.

Chemicals: Potassium hydroxide (KOH), hydrochloric acid (HCl), and phenolphthalein indicator, etc.

Preparation of 0.1 M potassium hydroxide solution:

Take properly weighed 06.00 gm of potassium hydroxide and add in 500 ml of distilled water, Once it has completely dissolved, make up the volume to 1000 ml with water.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
  • Titrate 20.0 ml of the solution with 0.1 M hydrochloric acid using 0.5 ml of phenolphthalein solution as an indicator,
  • The actual endpoint is indicated by the appearance of a violet color to blue.
  • To get accurate results, repeat the titration three times.
  • Properly record the readings of the burette.
  • Take their mean and calculate the molarity of the potassium hydroxide solution.
  • 1 ml of 0.1 M HCl is equivalent to 0.005611 g of KOH.

Observation table:

Sr. No.

Content in conical flask

 

Burette reading

Volume of titrant used (ml)

Initial

Final

1

 

 

 

 

2

 

 

 

3

 

 

 

 

Mean:

Result:

The strength of the prepared potassium hydroxide solution was found to be_____M.
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Preparation and standardization of 0.1 N potassium dichromate

Learn about the preparation and standardization of 0.1 N potassium dichromate solution through a laboratory experiment or practical.

Aim:

To prepare and standardize 0.1 N potassium dichromate solution using standard sodium chloride (volumetric solution).

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.

Chemicals: Potassium dichromate (K2Cr2O7), potassium iodide (KI), hydrochloric acid (HCL), sodium thiosulphate (Na2S2O3), and starch solution, etc.

Preparation of 0.1N potassium dichromate solution:

Take properly weighed 06.00 gm of potassium dichromate (It should be previously dried at 1200 C for 4 hours and cool in a desiccator) and add in 100 ml of distilled water, Once it has completely dissolved, make up the volume to 1000 ml with water.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
  • Take 40.00 ml of water and add 40.00 ml of prepared potassium dichromate solution in a stoppered flask.
  • Add 03.00 gm of potassium iodide and 05.00 ml of HCl.
  • Stopper the flask immediately, swirl to ensure even mixing, and then let stand for 10 minutes in the dark.
  • Rinse the stopper and interior walls of the flask with water, and titrate with freshly standardized 0.1N sodium thiosulphate solution until the solution becomes yellowish green.
  • Add 02.00 ml starch solution and continue the titration until the blue color disappears.
  • To get accurate results, repeat the titration three times.
  • Properly record the readings of the burette.
  • Take their mean and calculate the normality of the potassium dichromate solution.
  • 1 ml of 0.1 M sodium thiosulphate is equivalent to 0.0049 g of potassium dichromate.

Observation table:

Sr. No.

Content in conical flask

 

Burette reading

Volume of titrant used (ml)

Initial

Final

1

 

 

 

 

2

 

 

 

3

 

 

 

 

Mean:

Calculation:


A = B X C / D

Where,

A =normality of K2Cr2O7 solution
B = Na2S2O3 solution (ml) required for titration
C = Normality Na2S2O3 solution
D = K2Cr2O7 solution used


Result:


The strength of the prepared potassium dichromate solution was found to be_____N.


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