Preparation of a Primary Standard Solution
BSc Pharmaceutical Technology Practical - No 5
Preparation of a Primary Standard Solution
Aim: to prepare a standard solution of pure silver nitrate and use it to determine the concentration of chloride ions in a sample of tap water and another sample of bottled water.
Chemicals:
* High grade purity silver nitrate * Potassium chromate indicator * Tap water * Bottled water * Distilled water
Apparatus:
* Laboratory oven * Dessicator * Conical flask * Watch glass * Spatula * Glass rod * Burette * Funnel * Volumetric flask * Volumetric pipette
Setup: (see diagram under Discussion)
Procedure:
1). Weigh accurately approximately 4.5g of pure silver nitrate in powder form.
2). Place the watch glass with the powder in the drying laboratory oven for 30 minutes at a high temperature (60 – 100oC).
3). Take the sample out of the oven and place in the dessicator for about 10 minutes to cool down in dry conditions.
4). Weigh the powder once more to see the mass of actual silver nitrate now that it has lost the water of crystallization.
5). Wash the crystals into the volumetric flask using distilled water. Fill the flask with distilled water up to the 250ml mark shaking the solution well.
6). Place some of the solution of silver nitrate in the burette up to a suitable mark and note down.
7). Measure accurately 25ml of tap water and place in the conical using a volumetric pipette. Add three drops of potassium chromate indicator.
8). Place the conical flask underneath the burette and titrate the sample of water with the silver nitrate solution. Stop the titration when the end point (a slightly reddish colour) appears in the flask.
9). Repeat steps 7). and 8). until you have a rough estimate and 3 precise and accurate titre values.
10). Tabulate the results and use them to find the average titre value for this titration and so work out the concentration of chloride ions in the tap
Preparation of a Primary Standard Solution
Aim: to prepare a standard solution of pure silver nitrate and use it to determine the concentration of chloride ions in a sample of tap water and another sample of bottled water.
Chemicals:
* High grade purity silver nitrate * Potassium chromate indicator * Tap water * Bottled water * Distilled water
Apparatus:
* Laboratory oven * Dessicator * Conical flask * Watch glass * Spatula * Glass rod * Burette * Funnel * Volumetric flask * Volumetric pipette
Setup: (see diagram under Discussion)
Procedure:
1). Weigh accurately approximately 4.5g of pure silver nitrate in powder form.
2). Place the watch glass with the powder in the drying laboratory oven for 30 minutes at a high temperature (60 – 100oC).
3). Take the sample out of the oven and place in the dessicator for about 10 minutes to cool down in dry conditions.
4). Weigh the powder once more to see the mass of actual silver nitrate now that it has lost the water of crystallization.
5). Wash the crystals into the volumetric flask using distilled water. Fill the flask with distilled water up to the 250ml mark shaking the solution well.
6). Place some of the solution of silver nitrate in the burette up to a suitable mark and note down.
7). Measure accurately 25ml of tap water and place in the conical using a volumetric pipette. Add three drops of potassium chromate indicator.
8). Place the conical flask underneath the burette and titrate the sample of water with the silver nitrate solution. Stop the titration when the end point (a slightly reddish colour) appears in the flask.
9). Repeat steps 7). and 8). until you have a rough estimate and 3 precise and accurate titre values.
10). Tabulate the results and use them to find the average titre value for this titration and so work out the concentration of chloride ions in the tap