Preparation of Indicator Solutions

Preparation of Indicator Solutions

Preparation of Bromocresol Green Indicator:

Prepare 0.05% solution of Bromocresol greean by dissolving 50 mg of Bromocresol Green in 0.72 ml of 0.1M sodium hydroxide and 20 ml of ethanol (96%). Further add sufficient D/water to produce 100 ml.

Colour change:  At pH 3.6 it would have yellow color, by changing to pH 5.2 it would produce blue color.

Sensitivity test:

Prepare a mixture of 0.2 ml of the above solution and 100 ml of carbon dioxide-free water it will give blue color. Not more than 0.2 ml of 0.02M hydrochloric acid solution is required to change the color of the solution to yellow.

 

Preparation of crystal violet indicator:

Prepare 0.5% solution of crystal violet by dissolving 0.5g of crystal violet in 100ml of G. acetic acid.

Sensitivity Test:

Prepare a mixture of 0.1ml of the above solution and 50ml of the anhydrous acetic acid it will have bluish purple color. Now add 0.1ml of 0.1M per chloric acid to the mixture. The color of solution changes to bluish green.

Preperation of 1-naphthol benzein indicator:

Prepare 0.2% solution of 1-naphthol benzein by dissolving 0.2 g of 1-Naphthol Benzein in 100 ml of anhydrous acetic acid.

Sensitivity Test:

Prepare a mixture of 0.25ml of the above solution and 50ml of glacial acetic acid having brownish yellow color. Not more than 0.05ml of 0.1M HClO₄ is required to change the color of solution from brown to green.

Preparation of eosin y indicator:

Prepare 2.0% solution of eosin y indicator solution by dissolve 1g of Eosin Y in about 2ml of water and further add 50ml of alcohol.

Sensitivity Test:

N/A

Preparation of phenolphthalein indicator:

Prepare 0.1% solution by dissolving 100mg of Phenolphthalein in 80ml of alcohol and make volume up to100ml with D/water.

Sensitivity Test:

To 0.1ml of Phenolphthalein solution add 100ml of carbon dioxide free water. The solution is colorless. Not more than 0.2ml of 0.02 M Sodium hydroxide is required to change the color of solution to pink.

 

Preparation of Potassium chromate indicator:

Prepare 5% solution of potassium chromate indicator by dissolving 5 g of Potassium chromate in 80 ml of D/water and further add sufficient water to produce 100ml.

Sensitivity Test:

It would produce a red precipitate with silver nitrate Solution in neutral solution.

Preparation of Bromothymol Blue Indicator:

Prepare 0.05% solution of Bromothymol blue indicator by dissolving 50 mg of Bromothymol Blue in a mixture of 4 ml of 0.02M sodium hydroxide and 20 ml of ethanol (96%) and dilute to 100 ml with water (pH range, 6.0 to 7.6).

Sensitivity test:

A mixture of 0.3 ml of the solution and 100 ml of carbon dioxide-free water is yellow. Not more than 0.1 ml of 0.02M sodium hydroxide VS is required to change the color of the solution to blue.

 

Preparation of methyl Red Indicator:

Prepare 0.05% solution of Methyl red indicator by dissolving 50 mg of methyl red in a mixture of 1.86 ml of 0.1M sodium hydroxide and 50 ml of ethanol (96%) and add sufficient water to produce 100 ml.

 

Sensitivity test:

A mixture of 0.1 ml of the solution, 100 ml of carbon dioxide-free water and 0.05 ml of 0.02M hydrochloric acid VS is red. Not more than 0.1 ml of 0.02M sodium hydroxide VS is required to change the color of the solution to yellow.

Color change:  pH 4.4 (red) to pH 6.0 (yellow).

Preparation of Mordant Black Triturate R:

Prepare Mordant Black 11 by triturating a mixture of 1 part of mordant black 11 with 99 parts of sodium chloride.

Sensitivity to magnesium:

Dissolve 50 mg in 100 ml of water; a brownish violet color is produced. Add 0.3 ml of 6M ammonia; the color changes to blue. Add 0.1 ml of a 1% w/v solution of magnesium sulphate; the color changes to violet.

Store in an airtight container protected from light.

Preparation of Erichrome Black TS:

Prepare Erichrome Black test solution by dissolving 200mg of EBT and 2.0g of hydroxylamine hydrochloride in methanol and then make final volume up to 50 ml with the same solvent.

Preparation of Starch Solution:

Triturate 1.0 g of soluble starch with 5 ml of water and add, stirring continuously, to 100 ml of boiling water containing 10 mg of mercury (II) iodide.

Sensitivity test:

A mixture of 1 ml with 20 ml of water , about 50 mg of potassium iodide and 0.05 ml of 0.005M iodine VS is blue.

Preparation of Methyl Orange Indicator:

Prepare 0.1% solution by dissolving 100 mg of methyl orange in 80 ml of water and add sufficient ethanol (96%) to produce 100 ml.

Sensitivity:

A mixture of 0.1 ml of the solution and 100 ml of carbon dioxide-free water is yellow. Not more than 0.1 ml of 0.1M hydrochloric acid VS is required to change the color of the solution to red.

Color change:  pH 3.0 (red) to 4.4 (yellow).

Preparation of Phenol Red Solution:

Prepare 0.1% solution of Phenol Red solution by dissolving 100 mg of phenol red in 2.82 ml of 0.1M sodium hydroxide and 20 ml of ethanol (96%) and add sufficient water to produce 100 ml.

 

Sensitivity test:

A mixture of 0.1 ml and 100 ml of carbon dioxide-free water is yellow. Not more than 0.1 ml of 0.02M sodium hydroxide VS is required to change the color of the solution to reddish violet.

Color change:

pH 6.8 (yellow) to pH 8.4 (reddish violet).