7. Hold the test tube against a white background. Line up the tubes from lightest to darkest purple. The lighter the solution, the higher the vitamin C content. That's because vitamin C causes the purple indicator solution to lose its colour.
Testing for Chlorine
Add a few drops of Siver Nitrate to the solution. A white emulion is predicted if chlorine is present.
How to Test for Potassium Sorbate
Things You'll Need:
Acetone
Hydrochloric acid
Water
Filter paper
Chloride
Vacuum
Sulfuric acid
Bromine
Add one ml. of acetone to the sample. Dissolve the sample in dilute hydrochloric acid. The potassium sorbate will ionize to form sorbic acid in the chemical solution.
Dissolve the sample in water. If it is potassium sorbate, it will release sorbic acid.
Collect the precipitated sorbic acid on a filter paper.
Wash the filter paper free of chloride with water, and dry it under a vacuum over sulfuric acid.
Add a few drops of bromine solution. The color of the bromine solution disappears immediately.
Observe to see if there is potassium salt (cystalline powder that is white or slightly yellow), on the filter paper. Potassium sorbate is the potassium salt of sorbic acid.
However testing for potassium is not going to be carried out due to lack of apparatus and chemicals found in the laboratory.
Also some food labels were reaserched so that we could have a brief idea of what nutrients might be present in our powders:
Planning
Apparatus, materials, method and predictions
Apparatus: Several test tubes, beakers, measuring cylinder, digital balance and heating source.
Materials:
+ water
Method:
Step 1: 15cm3 of water will be added to 10g of each powder. In total there are 4 powders.
Step 2: For every powder we will preapre 6 test-tubes and put equal amounts of solution in each one.
Step 3: For each test we are going to put 6 drops of each reageant.
Step 4: For each powder we are going to test for:
Testing for Reduced Sugars:
-A few drops of blue Benedic’s solution will be added.
- The mixture will be heated in a water bath for several minutes.
Testing for Starch:
- A few drops of brown iodine will be added to the solution.
Testing for Proteins:
- A few drops of colourless concentranted Soduym hydroxide will be added to the solution.
-A few drops of blue copper sulphate will also be added.
Testing for Lipids:
- Ethanol will be used to extract the lipids from the food sample.
- Water will also be added (equal to ethanol).
Testing for Chlorine:
- A few drops of Sliver Nitrate will be added to the solution.
Testing for Vitamin C:
- A tablespoon of cornflower will be mixed with enought water to make a paste.
- 200 milliliters of water will be added to the paste and boiled for 5 minutes.
- 6 drops of starch solution will be added to 75 milliliters of water.
- Enough iodine will be added to produce a dark purple-blue color. (Indicator)
- 6 drops of indicator of solution will be placed in a test tube, were added to the cornflower.
- The test tubes from all the powders will be placed against a white background.
Step 5: Colour changes will be noted.
Step 6: Results will be presented in table form.
The table will look like this:
Predictions:
If the food is rich in the nutrient, these colours should be noted:
Method
Step 1: 15cm3 of water will be added to 10g of each powder. In total there are 4 powders.
Step 2: For every powder we will preapre 6 test-tubes and put equal amounts of solution in each one.
Step 3: For each test we are going to put 6 drops of each reageant.
Step 4: For each powder we are going to test for:
Step 5: Colour changes will be noted.
Step 6: Results will be presented in table form.
(The rest of the method remained the same).
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This was the predicted method. However while conducting the real experiment, we faced some problems. There was not enough powder as predicted. Instead we used 2.4g of power for each experiment. Also we decreased the amount of water used to 5cm3 as to have a balanced ratio. One final change was that we used 8 drops of reageant instead so the results will be more predictable. The experiment was conducted as follows:
Step 1: All the apparatus and materials mentioned before were set on the working table.
Step 2: For every powder (A, B, C, D) we conducted all the food tests. Therefore each powder was divided by 6 as to conduct a fair test. For every experiment 2.4 g of powder was used.
Step 3: In each test tube 5cm3 of water was added.
Step 4: Starting powder by powder, we tested for reducing sugars, starch, proteins, lipids, chlorine and Vitamin C.
Testing for Reduced Sugars:
- A few drops of blue Benedic’s solution were added.
- The mixture was than heated in a water bath for several minutes.
If present: Green to yellow to orange red precipitate should have formed.
Testing for Starch:
- A few drops of brown iodine solution were added to the sloution.
If present: Mixture should have been blue black.
Testing for Proteins:
- A few drops of colourless concentranted Soduym hydroxide were added.
-A few drops of blue copper sulphate were also added.
If present: Mixture should have been purple.
Testing for Lipids:
- Ethanol was used to extract the lipids from the food sample.
- Water was also added (equal to ethanol).
If present: The mixture should have turned into a cloudy, white emulsion.
Testing for Chlorine:
- A few drops of Sliver Nitrate were added to the solution.
If present: The solution should have turned white.
Testing for Vitamin C:
- A tablespoon of cornflower was mixed with enought water to make paste.
- 200 milliliters of water were added to the paste and boiled for 5 minutes.
- 8 drops of starch solution were added to 75 milliliters of water.
- Enough iodine was added to produce a dark purple-blue color. (Indicator)
- 5 milliliters of indicator of solution was placed in a test tube were added to the cornflower.
- The test tubes from all the powders were placed against a white background. The lighter the purple the more Vitamin C content as Vitamin C causes the purple indicator solution to loose its colour.
Results
Table of Results:
What does each powder contain?
D
-Reduced Sugars
-(Starch)
-Proteins
-Lipids
-Vitamin C
-Chlorine
C
-(Starch)
-Proteins
-Lipids
-(Vitamin C)
-Chlorine
B
-Reduced Sugars
- (Proteins)
-Lipids
-Vitamin C
-Chlorine
A
-Reduced Sugars
-Starch
-Proteins
-Lipids
-Chlorine
Evaluation
During the experiment, only 6 food tests were conducted. However each powder contains more nutrients than those that we actually tested for and therefore we could not have concluded the exect components of each powder. Looking at a food label there were other nutriens that we could have tested for like cholesterol, sodium, calcium, vitamin A, iron etc but due to limited time and sources, that was not possible.
As noted from the food label, next to each nutrient, there is the percentage (%) of each. However since no proffesional apparatus was used while conducting our tests, this could not have been achieved. Still, we could have concluded if the powder was rich in a certain nutrient judging of how much the colour obtained resembled the expected colour i.e. if we were expecting red, and it resulted yellow, it meant that it had a little bit of that nutrient but only traces.
Overall our method was pretty good. However if I was to conduct the experiment again I would vary it a little bit. For instance, the experiment would have been better if we had more of the powder. Also while pouring from a beaker to a test tube, some of the substance may have remained in the beaker, so the volumes may have not been as accurate. Another source of error was the number of drops of the reagent used. We used 8 drops for every experiment. However, if in some cases we had added, say 2 more drops, the result could have changed from negative to positive.
As discussed previously, if we had more time, we may have conducted another experiment, that the powder may have been rich in. For instance, I did find a method for tesing potassium but it needed a vacuum and several other chemicals which were not available in the laboratory.
However our overall result was pretty good, and I believe that we did solve Mr.Depasquale’s problem.
