Antacids.pdf

Inorganic compounds: Preparation, Properties, Assay, Use and Storage

1. Antacids
Presented by
Dr. Jasmine Chaudhary
Associate Professor
MMCP, MM(DU), Mullana

2. •Agents/substanceswhichneutralizetheexcessamountofacidingastrointestinaltractareknown
asantacids.
•Theyaregenerallyweakalkalinecompounds
•Onthebasisofinorganicelementalnatureitisdividedintomanycategories—
Calciumcontainingantacids—Calciumcarbonate,Tribasiccalciumphosphate.
Magnesiumcontainingantacids—Magnesiumhydroxide,magnesiumcarbonate,magnesium
oxide,magnesiumtrisilicate.
Aluminiumcontainingantacids—Aluminiumhydroxide,aluminiumphosphate,aluminium
carbonate,dihydroxyaluminiumsodiumcarbonate.
Sodiumcontainingantacids—Sodiumbicarbonate
Combinedantacids—AluminiumhydroxidegelandMg(OH)2.
AluminiumhydroxidegelandMagnesiumtrisilicate.
Aluminiumhydroxidegelandcalciumcarbonate

3. Calcium carbonate (CaCO
3)
Synonym: Precipitated Chalk/ Lime Stone
•Containsnotlessthan98%andnotmorethan102%ofCaCO
3calculatedwrtsampledriedat
105degreeC.
Preparation
1.Calciumcarbonateispreparedbythereactionofcalciumoxidewithwaterandcarbondioxide.
Initiallywaterisaddedtocalciumoxidethenitformscalciumhydroxidethecarbondioxideis
passedthroughthissolutiontoprecipitatethedesiredcalciumcarbonate.
CaO+ H
2O → Ca(OH)
2
Ca(OH)
2+ CO
2→ CaCO
3↓ + H
2O
2.Alsopreparedbyactionofcalciumchlorideonsodiumcarbonate
CaCl
2+ Na
2 CO
3 CaCO
3↓ + 2 NaCl

4. Physical Properties
Colorandstate—Whitishormilkycrystallinepowder.
Odorandtaste—Odorlesswithbittertaste.
Solubility—Practicallyinsolubleinwaterandethanol.Watersolubilityis
increasedinpresenceofcarbondioxideduetoformationofsolublecalcium
bicarbonate.
CaCO
3+H
2CO
3 Ca(HCO
3)
2
Uses
•Itisusedasfastactingantacidandincombinationwithmagnesiumcontaining
antacidsduetoitsconstipativeproperties.
•T/tofcalciumdeficiency
•Indentrifrices

5. Assay
•It is assayed by complexometric titration.
•Accurately weigh 0.1gm, dissolve in 3ml of dilute HCl, add 10ml of water.
Boil the solution for 10min, cool, dilute with 50 ml with water.
•Titrate the solution with 0.05M disodium EDTA to with a few ml of the
expected end point and add 8ml of NaOH solution and 0.1g of calconmixture.
Continue the titration until the color changes from pink to blue.
•Each ml of 0.05M disodium EDTA≡ 0.005004g of CaCO
3

6. Aluminium hydroxide gel Al(OH)
3(Mol wt: 78g)
Synonym: Aluminium hydroxide powder
•Itisanaqueoussuspensionofhydratedaluminiumoxidewithdifferentamountsofbasic
aluminiumcarbonateandbicarbonate.
•I.P.limit:Itcontainsnotlessthan3.5%andnotmorethan4.4%ofAl
2O
3
Preparation
Itispreparedbydissolvingsodiumcarbonateinhotwaterandthesolutionisfiltered.Tothefiltrate
addclearsolutionofalum(aluminiumsalt,chlorideorsulphate)inwaterwithconstantstirring
leadingtoprecipitationofaluminiumhydroxide
•Canalsobepreparedbyheatingaluminiumchloridewithammoniumhydroxide
AlCl
3
+ 3NH
4
OH Al(OH)
3
+ NH
4
Cl
3Na
2
CO
3
+ 2KAl(SO
4
)
2
+ 3H
2
O Na
2
SO
4
+ K
2
SO
4
+ Al(OH)
3
+ CO
2

7. Physical Properties
Whiteviscoussuspension
Smallamountofclearliquidmayseparateonstanding.
Solubleinacidsandalkalies.
Permittedtocontainsodiumbenzoateaspreservative
ChemicalProperties
ReactswithHCltoformaluminiumchloride
Al(OH)
3 + 3HCl AlCl
3
+ 3H
2
O
Uses:Aluminiumhydroxideisusedasantacidinthemanagementofpepticulcer,gastritis,gastric
hyperacidity.
Itisalsousedasskinprotectantandmildastringent.
Getconvertedtoaluminiumoxideonheating.
2Al(OH)
3 Al
2
Cl
3
+ 3H
2
O

8. Assay
Accurately weigh 5gm of sample and dissolve in 3ml HCl by warming on water bath, cool to
below 20 °C and dilute to 100ml with water.
To 20 ml of this solution add 40ml of 0.05M disodium EDTA, 80ml water, 0.15ml methyl
orange/red and neutralize by the dropwise addition of 1M sodium hydroxide.
Again warm on water bath for 30 min, add 3gm hexamine and titrate with 0.05M lead nitrate
using 0.5ml xylenol orange as indicator.
Each ml of 0.05M disodium EDTA ≡ 0.002549 gm of Al
2
O
3
DriedAluminiumHydroxideGel
Itanamorphousformofaluminumhydroxideinwhichthereisapartialsubstitutionof
carbonateforhydroxide.Itcontainstheequivalentofnotlessthan76.5percentofAl(OH)3,
anditmaycontainvaryingquantitiesofbasicaluminumcarbonateandbicarbonate.

9. Magnesium Trisilicate
2MgO.3SiO
2
. H
2
O (Hydrated Magnesium silicate, 260.86)
It contains 29-32% of magnesium oxide and not more than 65-68.5% of silicon dioxide both
calculated with reference to the ignited substance.
Preparation
Prepared from sodium silicate and magnesium sulphate
Na
2
O.SiO
2
+ MgSO
4
2MgO.3SiO
2
Physical Properties
•White fine powder free from grittiness.
•Odorlessand tasteless.
•Insloublein water and alcohol and hygroscopic in nature.
Chemical Properties
•Reacts with HCl yields magnesium chloride and trisilicacid.
2MgO.3SiO
2
+ 4HCl MgCl
2
+ H
2
SiO
3
+H
2
O

10. Assay
Magnesium oxide is assayed by complexometric titration by converting it to magnesium
chloride and silicon dioxide is assayed by gravimetric titration.
ForMagnesiumOxide:
Weighaccurately1gmsubstanceanddissolvein35mlofwaterallowtostandfor15minonwaterbath.
Coolthecontentstoroomtemperaturefilterandwashtheresiduewithwateranddilutethecombined
filtrateandwashingto250mlwithwater.
Neutralize50mlofthissolutionwithabout8mlof10MNaOHandthenadd10mlammoniabufferpH
10,50mgmordantblackIImixture.
Heatthecontentsto40°Candtitratewith0.05MdisodiumEDTAuntilcolorchangestodeepblue.
Each ml of 0.05M disodium EDTA≡ 0.002015g MgO

11. Forsilicondioxide:
Weighaccurately0.7gmofsubstanceadd10mlof1Msulphuricacid,10mlwaterandheatonwaterbathfor1.5hrs
withfrequentshaking.
Allowtocooldecantontoanashlessfilterpaper(7cmindiameter).Washtheprecipitatebydecantationwiththree
quantitieseachof5mlofhotwater,transferittothefilterpaperandwashitwithhotwater,until1mlofthefiltrate
remainsclearonadditionof2mlofbariumchloridesolutionand0.5mlof2NHCl.
Ignitethefilterpaperanditscontentsinatarredplatinumcrucibleat900°Ctoconstantweight.Theresidueis
silicondioxide.
Uses:Itisusedasnonsystemicantacidandadsorbent.
Inlargedoses,itinducesdiarrhea.
Alsousedasemulsifyingagentforoilswhenusedinlargerpreparations.
Storage:Storeinwellclosedcontaineratcoolplace.

12. Magnesium Carbonate
Itisahydratedbasicmagnesiumcarbonatecontaining40-45%ofmagnesiumoxide.
HeavyMagnesiumCarbonate:15goccupyavolumeofabout30ml
LightMagnesiumCarbonate:15goccupyavolumeofabout150ml
I.P.limit:Itcontainsnotlessthan40%andnotmorethan45%ofmagnesiumoxide
Preparation
Itispreparedbymixinghotsolutionofmagnesiumsulphateandsodiumcarbonate.
MgSO
4
+ Na
2
CO
3
MgCO
3
+ Na
2
SO
4
Properties
Bothheavyandlightmagnesiumcarbonatearehydrated.Botharewhite,odorlesspowderpractically
insolubleinwaterandalcoholbutsolubilizesindiluteacidswithstrongeffervescence.

13. Chemical Properties
•On heating, gets converted to MgO, losing carbon dioxide and water.
3MgCO
3
.Mg (OH)
2.
5H
2
O MgO+ CO
2
+6H
2
O
Assay
Magnesium carbonate is assayed by complexometric titration.
Weighaccurately1gmsubstanceanddissolveindiluteHClandvolumeismakeupto250mlwithwater.
To50mlofthissolution,add100mlwaterand15mlNaOH.Thenadd40mgmurexideand3ml
naphtholgreen.
Titratewith0.05MdisodiumEDTAuntilcolorchangestodeepblue.
Each ml of 0.05M disodium EDTA≡ 0.002015g MgO
Uses:Itisusedasantacidandlaxative.
Storage:Storeinwellclosedcontaineratcoolplace.

14. Sodium Bicarbonate (Sodium Hydrogen carbonate)
Baking soda, Cooking soda, Mithasoda (NaHCO
3
, 84.01g/mol)
Preparation
•Formedbyreactionofcarbondioxidewithaq.SolutionofNaOHwhichproducessodium
carbonate.Furtheradditionofcarbondioxideproducessodiumbicarbonate.
•FormedbyreactionofNaCl,ammoniumandcarbondioxide.
NaCl+NH
3
+H
2
O+CO
2
NaHCO
3
+NH
4
Cl
Physical Properties
•Odorlessand colorless.
•Crystalline powder.
•Freely soluble in water and insoluble in alcohol.
2NaOH + CO
2
Na
2
CO
3
+H
2
O
Na
2
CO
3
+H
2
O + CO
2
2NaHCO
3

15. Chemical Properties
NaHCO
3
+ 4HCl NaCl+ H
2
O + CO
2
NaHCO
3
+ NaOH Na
2
CO
3
+ H
2
O
Assay
It is assayed by acid base titration.
Weighaccurately1gmsubstanceanddissolveinwater.
Titratewith0.5MH
2
SO
4
usingmethylorangeasindicator.
Each ml of 0. 5M H
2
SO
4
≡ 0.0425g of NaHCO
3
Uses:Usedasantacid.
Electrolytereplenisher.
Storage:Storeinwellclosedcontaineratcoolplace.

16. Potassium citrate (C
6H
5O
7K
3 .H
2O)
Synonym: Potassium citrate, Kaliicitras, Tripotassiumcitrate
•ItcontainsNLT99%andNMT101%ofpotassiumcitrate.
Preparation
K
2
CO
3
+H
3
C
6
H
5
O
7
.H
2
O K
3
C
6
H
5
O
7
.H
2
O+3H
2
O+3CO
2
Properties
Colorless/Whitecrystalsorgranularpowder.
Odorlesshavingcoolsalinetaste.
Hygroscopic.
Solubleinwaterandglycerolandinsolubleinalcohol.
Athightemperature,evolvesinflammablegaseshavingpungentacridodor.
Assay
Dissolve200mgpotassiumcitratein25mlglacialaceticacid.Add2dropsofcrystalvioletindicatorand
titratewith0.1Nperchloricacidastitrant.
Eachmlof0.1Nperchloricacidisequivalentto10.21mgofK
3C
6H
5O
7

17. Uses
Diuretic, expectorant and diaphoretic.
Laxative & Alkalinising agent
Anticoagulant
Magaldrate: It is combination preparation.
•Composed of aluminium hydroxide and magnesium hydroxide.
•Contains equivalent of 28-39% MgO and 17-25% of Al2O3.
•White, colorless, crystalline powder.
•Insoluble in water and alcohol but soluble in dilute mineral acids.

18. Bismuth carbonate [(BiO
2)
2(CO
3)]
2. H
2O
Basiccarbonate,whichuponignitionyieldNLT90%andNMT92%ofBi
2O
3calculatedwith
referencetosubstancedriedat105°Cfor3hours.
Preparation
4Bi(NO
3
)
3
+ 6Na
2
CO
3
+ H
2
O [(BiO
2
)
2
(CO
3
)]
2
. H
2
O + NaNO
3
+ CO
2
Properties
White or pale yellowish white powder
Odorlessand tasteless.
Stable in air but slowly affected by light.
Insoluble in alcohol and water
Assay
It is assayed by gravimetric method. Accurately weighed amount is ignited in tarred crucible to
constant weight and then weight is analyte is calculated using gravimetric factor.
Use
Mild antacid
Adsorbantand Anti-diarrheal