Testing Effectiveness of Common
Antacids
4A
Danielle Friedman – Background & Hypothesis
David Hwang – Methods & Protocol
Ankur Patel – Deliverables & Pitfalls
Victoria Tsai – Equipment & Budget
Department of Bioengineering
Background:
Resistance of partly neutralized weak acids or bases present in aqueous
solution to change in pH is known as “buffering.” In various systems of the
body that require constant pH, buffers are used to control acidic or basic
conditions and keep enzymes and organs working at their pH optimum.
Antacids are over-the-counter drugs in tablet or liquid form that neutralize
acid and act as a buffer in the stomach. Most commercial antacids contain
calcium carbonate, magnesium hydroxide, or a combination of the two.
Hypothesis(es) & Aim(s) or Objective(s):
The buffer index of the active ingredients of three antacids, calcium
carbonate, magnesium hydroxide, and calcium carbonate + magnesium
hydroxide, will be compared to determine which is the most effective buffer
under physiological conditions. The combination of calcium carbonate +
magnesium hydroxide will be the most effective buffer and therefore have the
greatest buffering capacity.
Department of Bioengineering
Danielle Friedman
Methods & Protocol:
• Derive titration curve for both CaCO3 and Mg(OH)2
• Compare equal amounts equimolar solutions of both
antacids
• Titrate with standardized HCl solution
• Measure pH every .25 mL HCl added to generate large
sample count
• Analyze titration curve
• Calculate buffer index within stomach pH (1-3)
• Find effective pH range of buffer
• Find amount of acid antacid can neutralize
Department of Bioengineering
David Hwang
Proposed Deliverables/Findings:
• The Thymol Blue should cause the solution to change from yellow to red
at a pH of 1.2-2.8.
• From the titration curve determine the buffer index (volume of acid
neutralized) within the pH range of the stomach (1-3).
• The flat portion of the titration curve corresponds to the effective range of
the buffer. The inflection points of the titration curve correspond to the
pKa.
• CaCO3 should have 2 pKas due to CO3 having a charge of -2. Mg(OH)2
should have 1 pKa due to OH having a charge of -1.
Active
Neutralizing
Effective buffer range Ingredient
Capacity (pH)
CaCO3
1.0-4.5
Equivalence
Mg(OH)2
1.0-4.5
Point
CaCO3 +
1.0-4.5
Mg(OH)2
Halter 1983
Department of Bioengineering
Ankur Patel
Potential Pitfalls:
• If the titration does not produce a smooth curve and regions of
the curve are missing, too much HCl was added between
measurements.
• If the samples are not pure, the titration curves will not reflect
the true behavior of the antacids.
• If the molarity of the solutions are not accurate, then the buffer
index will be an inaccurate representation of the
effectiveness. However, the pH range of the flat portions of
the curve would not be affected by variability in molarity and
could be used as an alternative method of analysis.
Department of Bioengineering
Ankur Patel
Equipment/Materials and Budget & Justification:
Equipment - Needed to perform the titration of the two active ingredients
being tested.
• Two 50 mL burettes and burette stand, Balance, Magnetic stirrer and stirrer
bar, pH meter with combination glass-silver/silver chloride electrode and holder
Supplies - The following supplies include the two active ingredients being
tested and hydrogen chloride which will be used to titrate calcium carbonate
and magnesium hydroxide.
Calcium Carbonate (CaCO3), Supplier: Sigma-Aldrich (CAS Number: 471-341 ), $91.50/500g; Magnesium Hydroxide (Mg(OH)2), Supplier: Sigma-Aldrich
(CAS Number: 1309-42-8), $41.80/250g; Hydrogen Chloride (HCl), Supplier:
Sigma-Aldrich (CAS Number: 7647-01-0), $218.50/227g; Indicator: Thymol
Blue, Supplier: Sigma-Aldrich (CAS Number 76-61-9), 24.10/5g. Total:$375.90
Newly Purchased Equipment - No new equipment will be necessary. All the
equipment that is needed for this experiment is already present in the lab.
Department of Bioengineering
Victoria Tsai