I.INTRODUCTION

It is well known that the food we take undergoes a series of complex reactions within the body which constitute digestion and metabolism. These reactions are catalyzed by enzymes which are very specific in their action and can function properly only when the pH of the medium is within a specific range.

Some enzymes require mildly alkaline conditions while others operate only in weakly acidic media. Amongst the latter category of enzymes are the enzymes that control the digestion of proteins present in the food as it reaches the stomach. In the stomach, dilute hydrochloric acid is secreted and it provides mildly acidic conditions required for the functioning of protein digesting enzymes in the stomach.

Gastric acid is a digestive fluid, formed in the stomach. It has a pH of 1.5 to 3.5 and is composed of 0.5 % hydrochloric acid (HCl). It is produced by cells lining the stomach, which are coupled to systems to increase acid production when needed.

Other cells in the stomach produce bicarbonate to buffer the acid, ensuring the pH does not drop too low (acid reduces pH). Also cells in the beginning of the small intestine, or duodenum, produce large amounts of bicarbonate to completely neutralize any gastric acid that passes further down into the digestive tract. The bicarbonate-secreting cells in the stomach also produce and secrete mucus. Mucus forms a viscous physical barrier to prevent gastric acid from damaging the stomach.

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However, sometimes the stomach begins to secrete an excess of HCl. This leads to a condition known as Gastric Hyperacidity. This condition can also be triggered by the intake of too much food or highly spiced food. This, in turn, makes the stomach lining cells to secrete more acid resulting in Hyperacidity. It also leads to acute discomfort due to indigestion.

To counter this situation, substances like Antacids or literally anti - acids, have been developed. Antacids are commercial products that neutralize the excess acid in the stomach providing a sensation of relief to the person. The action of antacids is based on the fact that a base can neutralize an acid forming salt and water.

Common antacids satisfy the condition – right amount of alkali that can neutralize the acid. If the content of alkali in the antacid is too high, no doubt acidity is relieved, but it’ll create alkaline conditions that makes the digestive enzymes ineffective.

To make sure that the pH of the stomach remains in a specific range, many substances are added to the antacids.

Working of Antacids:

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If the antacid contains NaHCO3 then the reactions that occur in the

stomach are:

Na+

+ HCO3- +

H+

+

Cl-

NaCl + H2CO3

H2CO3 H2O + CO2

The excess Na+ and HCO3- ions are absorbed by the walls of the small intestines

as the food passes through

The H2CO3 formed during the reaction decomposes rapidly to form water and carbon dioxide gas.

Types of Antacids:

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Sodium Antacids (Alka-Seltzer, Bromo-Seltzer and Others): Sodium bicarbonate (commonly known as baking soda) is perhaps the best-known of the sodium-containing antacids. It is potent and fast-acting. As its name suggests, it is high in sodium. If you're on a salt-restricted diet, and especially if the diet is intended to treat high blood pressure (hypertension), take a sodium-containing antacid only under a doctor's orders.

Calcium Antacids (Tums, Alka-2, Titralac and Others): Antacids in the form of calcium carbonate or calcium phosphate are also potent and fast-acting. Regular or heavy doses of calcium (more than five or six times per week) can cause constipation. Heavy and extended use of this product may clog your kidneys and cut down the amount of blood they can process. Extended use of calcium antacids can also cause kidney stones.

Magnesium Antacids (Maalox, Mylanta, Riopan, Gelusil and Others): Magnesium salts come in many forms -- carbonate, glycinate, hydroxide, oxide, trisilicate, and aluminosilicate. Magnesium has a mild laxative effect; it can cause diarrhea. For this reason, magnesium salts are rarely used as the only active ingredients in an antacid, but are combined with aluminum, which counteracts the laxative effect. (The brand names listed above all contain magnesium-aluminum combinations.) Like calcium, magnesium may cause kidney stones if taken for a prolonged period, especially if the kidneys are functioning improperly to begin with. A serious magnesium overload in the bloodstream (hypermagnesaemia) can also cause blood pressure to drop, leading to respiratory or cardiac depression -- a potentially dangerous decrease in lung or heart function.

Aluminum Antacids (Rolaids, ALternaGEL, Amphojel and Others): Salts of aluminum (hydroxide, carbonate gel, or phosphate gel) can also cause constipation. For these reasons, aluminum is usually used in combination with the other three primary ingredients. Used heavily over an extended period, antacids containing aluminum can weaken bones, especially in people who have kidney problems. Aluminum can cause dietary phosphates, calcium, and fluoride to leave the body, eventually causing bone problems such as osteomalacia or osteoporosis.

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Side effects::

Calcium: Excess calcium from supplements, fortified food and high-calcium diets, can cause milk-alkali syndrome, which has serious toxicity and can be fatal.

Carbonate: Regular high doses may cause alkalosis, which in turn may result in altered excretion of other drugs, and kidney stones. A chemical reaction between the carbonate and hydrochloric acid may produce carbon dioxide gas. This causes gastric distension which may not be well tolerated. Carbon dioxide formation can also lead to headaches and decreased muscle flexibility.

Aluminum hydroxide: May lead to the formation of insoluble aluminium-phosphate-complexes, with a risk for hypophosphatemia and osteomalacia. Although aluminium has a low gastrointestinal absorption, accumulation may occur mainly in the presence of renal insufficiency. Aluminium-containing drugs often cause constipation and are neurotoxic.

Magnesium hydroxide: Has laxative properties. Magnesium may accumulate in patients with renal failure leading to hypermagnesaemia, with cardiovascular and neurological complications.

Sodium: increased intake of sodium may be deleterious for arterial hypertension, heart failure and many renal diseases.

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Heartburn, reflux, indigestion, and sour stomach are a few of the common terms used to describe digestive upset. Self-diagnosis of indigestion does carry some risk because the causes can vary from a minor dietary indiscretion to a peptic ulcer.

 The pain and symptoms of GERD or simply "reflux” may mimic those of a heart attack. Misdiagnosis can be fatal. A bleeding ulcer can be life threatening.

 GERD and pre-ulcerative conditions in the stomach are treated much more aggressively since both, if untreated, could lead to esophageal or stomach cancer.

 It is primarily for this reason that the H2 blockers including cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac), and the proton pump inhibitor (PPI) omeprazole (Prilosec) were made OTC.

These drugs stop production of stomach acid and provide longer lasting relief but they do not neutralize any stomach acid already present in the stomach.

Problems with reduced stomach acidity:

Reduced stomach acidity may result in an impaired ability to digest and absorb certain nutrients, such as iron and the B vitamins. Since the low pH of the stomach normally kills ingested bacteria, antacids increase the vulnerability to infection. It could also result in the reduced bioavailability

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of some drugs. For example, the bioavailability of ketocanazole (anti-fungal) is reduced at high intragastric pH (low acid content).

Over usage of antacids naturally have side-effects. As with anything in life, it must

be used in moderation. The following flowchart elucidates very clearly.

II.OBJECTIVE

This project aims at analyzing some of the commercial antacids to determine which one of them is the most effective by conducting a quantitative analysis.

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Motives behind selecting this research project:

Consumerism, in the era of global industrialization, plays a very important role. There are various product options available for consumers to choose from. Different manufacturers selling their products, attempting to sway public opinion in their favor, marketing their products regardless of their effectiveness in functionality. Hence it becomes the consumer’s right to experiment and know the most effective, efficient, and value for money product. There are various methods to conclude that a product out of all the given competitors is the best. Experimental research is the most rational and convincing one of those methods. The result of this analysis could be used to inform oneself as to which antacid is the best and provides best relief.

Apart from the economic perspective, the titrations that are conducted as a part of this experiment is in itself an attracting aspect. The prospect of making color changing solutions, the thrill of chemical reactions, and conducting them with accuracy is probably the most interesting part of titrations and the whole project.

III.THEORY

Antacids react with excess stomach acid by neutralization.

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i.e. HCl + NaOH → H2O + NaCl

During the process, hydrogen ions H+ from the acid (proton donor) or a

hydronium ion H3O+ and hydroxide ions OH- from the base (proton acceptor) react

together to form a water molecule H2O. In the process, a salt is also formed when

the anion from acid and the cation from base react together. Neutralization

reactions are generally classified as exothermic since heat is released into the

surroundings.

Acids are proton donors which convert into conjugated bases. They are generally

pure substances which contain hydrogen ions (H-) or cause them to be produced in

solutions. Hydrochloric acid (HCl) and sulfuric acid (H2SO4) are common

examples. In water, these break apart into ions:

HCl → H+(aq) + Cl-(aq) OR

H2SO4 → H+(aq) + HSO3-(aq)

Bases are proton acceptors which convert into conjugated acids. They are generally

substances which contain hydroxide ion (OH-) or produce it in solution. Alkali

bases are the soluble bases, i.e. a base which contains a metal from group 1 or 2 of

the periodic table. To produce hydroxide ions in water, the alkali breaks apart into

ions as below:

NaOH→ Na+(aq) + OH-(aq)

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Examples of bases include sodium hydroxide (NaOH), potassium hydroxide

(KOH), magnesium hydroxide (Mg(OH)2), and calcium hydroxide (Ca(OH)2).

Antacids are generally bases.

Explanation of action of neutralization of antacids:

The Lewis definition of acid-base reactions is a donation mechanism, which

conversely attributes the donation of electron pairs from bases and the acceptance

by

acids.

Ag + + 2 :NH3 → [H3N: Ag :NH3]+

(A silver cation reacts as an acid with ammonia which acts as an electron-pair

donor, forming an ammonia-silver adduct)

In reactions between Lewis acids and bases, there is the formation of an adduct

when the highest occupied molecular orbital (HOMO) of a molecule, such as NH3

with available lone electron pair(s) donates lone pairs of electrons to the electron-

deficient molecule's lowest unoccupied molecular orbital (LUMO) through a co-

ordinate covalent bond; in such a reaction, the HOMO-interacting molecule acts as

a base, and the LUMO-interacting molecule acts as an acid. In highly-polar

molecules, such as boron trifluoride (BF3), the most electronegative element pulls

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electrons towards its own orbitals, providing a more positive charge on the less-

electronegative element and a difference in its electronic structure due to the axial

or equatorial orbiting positions of its electrons, causing repulsive

effects from lone pair-bonding pair (Lp-Bp) interactions between bonded atoms in

excess of those already provided by bonding pair-bonding pair (Bp-Bp)

interactions.

Determination of concentrations of substances in neutralization:

The experimental method about neutralization is the acid-base titration. An acid-

base titration is a method that allows quantitative analysis of the concentration of

an unknown acid or base solution. It makes use of the neutralization reaction that

occurs between acids and bases, and that we know how acids and bases will react

if we know their formula.

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Before starting the titration a suitable pH indicator must be chosen. In this project,

phenolphthalein is chosen. The endpoint of the reaction, the point at which all the

reactants have reacted, will have a pH dependent on the relative strengths of the

acid and base used. The pH of the endpoint can be estimated using the following

rules:

• A strong acid will react with a strong base to form a neutral (pH=7) solution.

• A strong acid will react with a weak base to form an acidic (pH<7) solution.

• A weak acid will react with a strong base to form a basic (pH>7) solution.

Phenolphthalein is used to determine the end point of the titration which indicates

complete neutralization. In the presence of, an acid solution is colourless, a basic

solution is very dark pink, and a neutral solution is very pale pink. At this point the

solution is very slightly basic, with a negligible amount of excess NaOH. By

keeping track of exactly how much NaOH is needed to complete the neutralization

process, the amount of HCl originally neutralized by the antacid can be calculated.

The difference between the number of moles of HCl initially added to the antacid

and the number of moles of HCl neutralized by the NaOH during the titration is the

number of moles neutralized by the antacid. Several antacids will be tested and the

relative strengths of each will be compared.

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Nature of phenolphthalein:

Phenolphthalein is a chemical compound with the formula C20 H14 O4. It is

insoluble in water, and is usually dissolved in alcohols for use in experiments. It is

itself a weak acid, which can lose H+ ions in solution. The phenolphthalein

molecule is colorless. However, the phenolphthalein ion is pink. When a base is

added to the phenolphthalein, the molecule⇌ ions equilibrium shifts to the right,

leading to more ionization as H+ ions are removed. This is predicted by Le

Chatelier's principle.

++++++++++++++++++++++ HYPOTHESIS+++++++++++++++++++++++++

Our hypothesis is that the greater proportion of the active ingredient with

stronger base in an antacid tablet will have the greater neutralizing power.

And thus, it will be more effective to cure upset stomach.

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IV.MATERIALS REQUIRED

The following were the materials required for the project:

a. A

p p a r a t u s :

1. Burette(50 ml)2. Pipette(20 ml)3. Conical Flasks(250 ml)4. Measuring Cylinder(10 ml)5. Beakers(100 ml)6. Standard Flasks(100 ml)7. Filter Paper8. Funnel9. Bunsen Burner

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Bunsen Burner Beaker

10.Weighing machine11.Clean & glazed white tile12.Glass Rod13.Water14.Crusher

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BuretteConical Flask Dropper

Glass rods

b. C h e m i c a l s :

1. NaOH powder2. Na2CO3 powder

3. 10 M conc. HCl acid4. Four different brands of antacids5. Phenolphthalein6. Methyl Orange

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Antacids Phenolphthalein Solution

NaOH Powder

10M HCl Solution

Na2CO3 powder

V.PROCEDURE

1. First prepare approximately 1 litre of approximately N/10 solution of HCl by

diluting 10 ml of the given 10M HCl acid to 1 litre.

10 ml -10M HCl

Approx. 1 L H2O

1 L - 0.1M HCl

2. Next prepare 1 litre of approx. N/10 NaOH solution by dissolving 4.0g ofNaOH powder to make 1 litre of solution.

4.0g NaOH

A pprox. 1 L H2O

1 L - 0.1M HCl

3. Similarly prepare N/10 Na2CO3 solution by weighing exactly 1.325g of

anhydrous Na2CO3 and then dissolving it in water to prepare exactly 0.25 L or

250 ml of Na2CO3 solution.

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4. Now, standardize the HCl solution by titrating it against the StandardNa2CO3 solution using methyl orange as indicator.

B u r e tt e : 0.1N HCl

F l a s k : 0.1N Na2CO3 + Methyl Orange

5. Similarly standardize the NaOH solution by titrating it against standardized HCl solution using phenolphthalein as indicator. Stop the titration when the pink color of the solution disappears.

B u r e tt e : 0.1N HCl

F l a s k : 0.1N NaOH + Phenolphthalein

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6. Now, powder the four antacid samples and weigh 0.5 g of each.

1.0 g

7. Add 25 ml of the standardised HCl to each of the weighed samples taken in conical flasks. Make sure that the acid is in slight excess

so that neutralise all the basic character of the tablet powder.

25ml 0.1N HCl

8. Add a few drops of phenolphthalein indicator and warm the flask over a Bunsen burner till most of the powder dissolves.

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9. Filter the insoluble material.

10.Titrate this solution against the standardised NaOH solution, till a permanent pinkish tinge ins obtained.

11.Repeat the same experiment for all other samples too.

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VI.PRECAUTIONS

1. Avoid touching the antacid with your fingers.

2. Be careful not to lose any solid when crushing the antacid tablet.

3. Avoid touching hot surfaces when working near the hot plate and be

cautious when transporting heated solutions.

4. The hot plate should not be left unattended .

5. Dilute HCl and NaOH were corrosive and can damage your eyes and

cause skin irritation.

6. The burette must be rinsed out with NaOH before use to prevent dilution

of the solution.

7. It should be made sure that there were no air bubbles in the burette tips.

8. Burette readings should be recorded to the nearest 0.05 cm3.

9. Sodium hydroxide should be removed from the burette as soon as

possible after the titration. It was because NaOH is corrosive and it

reacted with carbon dioxide in the air to form sodium carbonate which

was a white solid and clogged the tip of the burette easily.

10.Rinse all apparatus thoroughly using Distilled water. Any residual

chemicals could cause variations in pH readings.

11.Tap on the weighing machine after it shows required value to confirm a

precise reading

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12.Pipette out the solutions carefully as it is possible to accidentally ingest

the solution.

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VII.OBSERVATIONS

Standardisation of HCl solution:

Volume of 0.1N Na2CO3 taken = 20 ml Indicator used = Methyl Orange

SERIALNo.

BURETTE READINGS VOLUME OF ACID USED

(ml)INITIAL READING FINAL READING

1.2.

018

1735

1717

Applying normality equation, N1 V1 = N2 V2

(acid) (base) N1 x 17 = 0.1 x 20 Normality of HCl, N1= 2/17 = 0.11 ≈ 0.1

Standardization of NaOH Solution: Volume of the given NaOH solution taken = 20.0 ml Indicator used = Phenolphthalein

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SERIALNo.

BURETTE READINGS VOLUME OF ACID USED

(ml)INITIAL READING FINAL READING

1.2.

017

1633

1616

Volume of acid used = 16 ml Applying normality equation, N1 V’1 = N’2 V’2 (acid) (base) 0.11 x 16 = N’2 x 20 Normality of HCl, N’2 = (0.11*16)/20 = 0.09 ≈ 0.1

Analysis of antacid tablets:

Weight of the antacid tablet powder = 0.5 g Volume of HCl solution added = 30 ml Volume of sample solution taken = 20 ml

for titration

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ANTACID VOLUME OF (NaOH) USED FOR NEUTRALIZING

UNUSED (HCL) 1.Eno Pineapple 2. Eno Lemon 3.Digene Lime 4.Omez 5. Pephyrous 6. Gelusil

29249244022

VIII.RESULT

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1g of Eno Pineapple required 29 ml of Sodium Hydroxide (NaOH) to titrate it completely.

1 g of Eno Lemon required 24 ml of Sodium Hydroxide (NaOH) solution to titrate it completely.

1 g of Digene lime required 9 ml of Sodium Hydroxide (NaOH) to titrate it.

1 g of Omez required 24 ml of Sodium Hydroxide (NaOH) to titrate it completely.

1 g of Pephyrous required 40 ml of Sodium Hydroxide (NaOH) to titrate it completely.

1 g of Gelusil required 22 ml of Sodium Hydroxide (NaOH) to titrate it completely.

Based on the hypothesis of the experiment, the antacid which requires the least amount of Sodium Hydroxide (NaOH) is the best antacid. From the recorded observation, Digene© requires the least (5 ml), and is therefore the best Antacid.

IX.SUMMARY AND CONCLUSION

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Antacids play a very important role in relieving many patients suffering from gastric hyperacidity, commonly referred to as gastritis. This project was undertaken to analyze the best commercially available antacid according to the amount of hydrochloric acid they could neutralize.After exploring many books and websites to find out more about antacids, we were clear of its role and its applications. We started our project by powdering the various antacid samples and making sure that the apparatus were clean. Later we standardized various solutions and prepared N/10 HCl solution and N/10 NaOH solution. This was done by titrating various solutions and using the respective indicators.The powdered antacid samples weighing 1 gram each was each added to 30 ml of the standardized solution of HCl in separate conical flasks. These solutions were later titrated with the standardized NaOH and the readings were noted. These readings were helpful in deciding the amount of HCl that each antacid could neutralize. Various antacids could neutralize a specific amount of the acid. pephyrous was the poorest among all antacids. Eno pineapple had a slightly higher alkaline nature while Eno lemon and Omez proved to neutralize to same amount . Gelusil had a higher concentration of the base. Digene had the highest basic character!Thus, on the basis of the experiment conducted, it was adjudged that Digene was the best commercially available antacid.

X.BIBLIOGRAPHY

WEBSITES:

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http://www.reachoutmichigan.org/funexperiments/quick/csustan/antacid http://icn2.umeche.maine.edu/genchemlabs/Antacid/antacid2.htm http://www.chem.latech.edu/~deddy/chem104/104Antacid.htm http://www.images.google.com http://www.wikipedia.com http://www.pharmaceutical-drug-manufacturers.com

BOOKS:

Comprehensive Practical Chemistry Class XII

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