Determination of Percent A.S.A
Cost Effectiveness and Related Tests
(A.S.A. is acetyl salicylic acid)
Procedures
Part 1 Percent ASA
Carefully weight single tablets of various brands of aspirin to two decimal places.
Record the mass of each tablet on the data sheet.
Determine the amount of ASA per tablet, as stated on the label.
Determine the cost per tablet from the price sticker on the outside of the bottle.
Make sure you include the tax.
Calculate the percentage of ASA/tablet. Record this data.
Part 2 Test for Reducing Sugars
A substance other than ASA is needed to give the bulk and to keep it from
crumbling. Lactose, a sugar, is often added to some brands. Others contain
starch. This part of the lab is a test for a reducing sugar such as lactose.
Aspirin will not dissolve in water, but it can be crushed and dispersed to form a
fine suspension. Using a small mortar and pestle, crush one tablet of each brand
and place them in clean labelled test tubes. Add 15 mL of distilled water and
shake them. These are your stock solutions. Transfer 5 mL of each stock solution
to separate test tubes. save the remainder of your stock solution for other tests.
Test each of the 5 mL solutions with blue litmus paper. To each solution which is
acidic, add saturated sodium carbonate solution a drop at a time. Test with your
blue litmus paper after adding each drop, until the blue litmus no longer turns
pink. To each of the neutralized solutions, add 5 mL of Benedict's solution and
heat the tubes to boiling in a water bath. A reducing sugar, like lactose, is one
which will chemically reduce the blue cupric ions of Benedict's solution to
cuprous ions. The colour of the cuprous precipitate which forms will range from
yellow to orange to brick red depending upon how much reducing sugar is
present. Record the colours in the data table.
Part 3 Test for Salicylic acid
To a clean set of test tubes add 5 mL of your stock solutions. To each test tube add
10 drops of 0.1 M iron(III) nitrate solution.
A violet colour indicates that the salicylic acid of ASA has reacted with the ferric
ions. This is a positive test for the presence of salicylic acid. Record the colour
acquired.
Part 4 Test for Starch
To the remaining stock solution, add 3-5 drops of iodine solution. A bluish-black
colour indicates the presence of starch. Record these colours in the data table.
Analysis
1. Analyze the results of your experiment by including the following in your lab
report.
a) difference in ASA % amongst brands
b) other substances in the tablets
c) results of the iron nitrate test
d) cost per tablet
e) consumer considerations (best buy)
Questions
1. Why is aspirin referred to as:
a) an analgesic
b) an antipyretic?
2. In the experiment, a saturated sodium carbonate solution was used. Assuming
that the solubility curve of sodium carbonate is linear, show how you can
determine the amount of sodium carbonate needed to be added to 500 mL of
water at 20oC to achieve saturation.
DATA: Solubility in grams at 0oC = _____7.1 g_
Solubility in grams at 100oC = ___45.5 g_
3. Calculate the number of grams of ferric nitrate nonahydrate in 10.0 L of a
0.1 M solution.
4. What is the structure and formula for lactose?
5. Benedict's solution is made in the following way
173 grams of sodium citrate
100 grams of sodium carbonate in 800 mL of water
17.3 g of cupric sulphate pentahydrate in 100 mL of water
Dilute to 1000 mL.
Calculate the concentration of the following in this solution.
a) sodium citrate
b) sodium carbonate
c) cupric sulphate