Expectorant, Types, Mechanism of Action, Potassium iodide, Ammonium chloride, Preparation, Properties, Test for purity, Identification test, Assay, uses, Storage, Standard.

1. EXPECTORANTS
GRACE SHAJI CHITTILAPPILLY
ASSISTANT PROFESSOR
DEPT. OF PHARMACEUTICAL CHEMISTRY
KARPAGAM COLLEGE OF PHARMACY, COIMBATORE-32

2. CONTENTS
• INTRODUCTION
• MOA
• POTASSIUM IODIDE
• AMMONIUM CHLORIDE

3. INTRODUCTION
• Expectorants are drugs which enhances the secretion of the sputum by the
air passages so that it is easier to remove the phlegm through coughing.
• They act either by increasing the bronchial secretion or by making it less
viscous (mucolytic agents).
• Cough is a protective physiological reflex to clear the airway.
COUGH
Irritative cough
(Dry cough) Productive cough

4. 1) Irritating Cough
o Produced by cold or by inhalation of irritating dust or gases
o Produces no sputum or other discharges
2) Productive Cough
o Sputum or exudate producing cough
o Associated with asthma or bronchitis
• Expectorants – Increases volume of secretion in respiratory tract facilitate
their removal by ciliary action & coughing
• Examples:
Terpine hydrate – direct effect on bronchial secretory cells
Ammonium chloride, Glyceryl guaiacolate, Iodinated glycerin, Potassium iodide,

5. Antimony potassium tartrate, Syrup of ipecac.
• Natural example : Ipecacuanha – stimulant expectorant.
Irritate the lining of the stomach
Reflexly stimulates the stimulates the production of sputum by the glands in the
bronochial mucous membrane.
• Potassium iodide and Ammonium chloride Stimulates the gastric mucosa &
reflexly increases bronchial secretions.

6. POTASSIUM IODIDE, KI
• PREPARATION
1. Preparation by Iodine
 Slight excess of iodine Solution of Potassium iodide mixture of
Potassium iodide and iodate.
 Iodate reduced Iodide by heating with charcoal
6KOH + 3I2
5KI + KIO3 + 3H2O
potassium
hydroxide
iodine potassium
iodide
potassium
iodate

7. 2. Preparation by Iron fillings
 Treating iron fillings with iodine in water Ferrous iodide is formed
reduced with potassium carbonate.
3. Preparation with hydriodic acid
 Hydriodic acid rn with Potassium bicarbonate Pot. iodide
KIO3 + 3C KI + 3CO
potassium
iodide
potassium
iodate
Fe + I2 FeI2
K2CO3 + FeI2 2KI + FeCO3
ferrous
iodide
Pot.
iodide

8. • CHARACTERISTICS
 Colourless
 Odourless
 Transparent/ opaque crystals or white granular powder
 Slightly hygroscopic / deliquescent
 Taste is saline & slightly bitter
 Stable in dry air
 Solubility – soluble in water , alcohol, glycerol
 Long exposure to air become yellow due to liberation of iodine & small quantity
KHCO3 + HI KI + H2CO3
carbonic acid
Pot.
bicarbonate
Hydriodic
acid
Pot.
iodide

9. of iodate.
 light and moisture accelerate rate of decomposition.
 Aqu. Solution of KI yellow colour due to oxidation small amt of alkali prevents
its oxidation.
• INCOMPATIBILITY
 Incompatible with alkaloidal salts, chloral hydrate, tartaric and other acids, calomel, Potassium
chlorate and metallic salts.
• TEST FOR IDENTITY
1) Potassium – refer Potassium citrate (Systemic Antacid)
2) Iodide
 Test 1: sample soln + dil HNO3 + Silver nitrate Curdy yellow precipitate of Silver iodide.

10.  Test 2: Soln of iodide + Mercuric chloride soln Dark red precipitate.
 Test 3: Sample soln + H2SO4 + Potassium dichromate violet coloured iodine
Few ml chloroform added & shaken & allowed to settle
Chloroform layer is coloured violet or violet-red.
• TEST FOR PURITY
1. Alkalinity
2. Arsenic
3. Heavy metals
4. Barium

11. 5. Cyanide
6. Iodate
7. Loss on drying
8. Clarity and colour of solution
9. Iron
10. Thiosulphate
 Test for Alkalinity
An aqueous solution of potassium iodide containing a drop of 0.02N sulphuric acid
Addition of phenolphthalein solution
No colour – absence of alkaline impurities.

12.  Test for barium
To solution add dilute sulphuric acid
No turbidity developed within 1 min barium not present
 Test for cyanides
Ferrous sulphate soln (1 drop) & NaOH soln (0.5 ml) added to aqu. Solution of
substance
Reaction mixture acidified with HCl
No blue colour – absence of cyanides.

13.  Test for Iodates
Treat aqu solution with dilute H2SO4 + starch solution
No blue colour produced within 2 min – absence of iodates
• STORAGE : Deliquescent slightly in moist air, Store in well-closed container &
protected from light.
• STANDARD: Contains not less than 99% and not more than 100% of KI
calculated with reference to the dried substance.

14. • ASSAY
10ml of KI soln diluted with water + HCl + Potassium cyanide
Titrated with M/20 potassium iodate
Until dark brown solution becomes pale yellow, then solution of starch added
Titration continued, till end point: disappearance of blue colour
KIO3 2KI 3KCN 6HCl 6KCl 3ICN 3H2O
+ + + + +
KIO3 2I2 6HCl KCl 5ICl 3H2O
+ + + +

15. • MEDICINAL AND PHARMACEUTICAL USES
 Expectorant
 Source of Iodine
 Ingredient in many laboratory reagents (Mayer’s reagent and Nessler’s reagent)
 Antifungal
 Antitussive

16. AMMONIUM CHLORIDE, NH4Cl
• PREPARATION
1) Neutralization of Hydrochloric acid with ammonia and evaporation of
solution to dryness – Ammonium chloride.
2) By boiling Ammonium sulphate solution with sodium chloride in equivalent
proportions.
NH3 + HCl NH4Cl
Ammonium
chloride

17. • CHARACTERISTICS
 White crystalline powder or colourless crystals
 Odourless
 Cooling saline taste
 Somewhat hygroscopic and strongly endothermic
 Sublimes without melting
 Solubility:
Freely soluble in water and glycerol
more soluble in boiling water
(NH4)2SO4 + 2NaCl 2NH4Cl + Na2SO4
Ammonium
sulphate
Ammonium
chloride

18. Sparingly soluble in alcohol
Almost insoluble in acetone, ether and ethyl acetate
* Hydrochloric acid & Sodium chloride decreases solubility in water.
* 5% solution of NH4Cl – pH 4.6 – 6.0
 When heated , ammonium chloride volatilises – decompose into ammonia and HCl but
reunite when cooled used as flux in soldering for removing film of oxide from
surface of metal.
 Ammonium chloride solution is neutral when freshly prepared , it becomes slightly acid on
standing due to hydrolysis.
 Play an important role in maintenance of acid-base equilibrium of body (acidosis)
 Diuretic effect of NH4Cl – due to formation of a proton and chloride ion, equivalent to
HCl.
NH4Cl NH3 + HCl

19. • INCOMPATIBILITY
 It gives the reactions of ammonium salts and of chlorides.
• TEST FOR PURITY
 Arsenic
 Heavy metals
 Lead
 Iron
 Barium
 Sulphate
 Thiocyanate
 Sulphated ash

20.  loss on drying
 Non-volatile matter
 Test for Barium
Aqu solution + dil. H2SO4 No turbidity with in 2 hrs Absence of barium.
 Test for Thiocyanate
Acidified solution with HCl add few drops of ferric chloride no red colour
absence of thiocyanate

21.  Loss on drying
Dry sample in an oven at 105oC
NH4Cl volatilizes dry in desiccator containing H2SO4.
• TEST FOR IDENTITY
1. Ammonium
(a) Test – 1
Soln heated with NaOH
Ammonia produced

22. Recognized by strong, pungent & characteristic odour
Turns moist red litmus paper blue.
(b) Test – 2
Aqu soln + light Magnesium oxide
Ammonia evolved passed through dil. soln of 0.1M HCl
Containing methyl red (indicator) till soln becomes yellow
Freshly prepared Sod. Cobaltinitrite soln added yellow ppt
(Ammonium sodium cobaltinitrite)

23. 2. Chlorides
(a) Test – 1
Aqu soln with dil. HNO3 + silver nitrate
White ppt AgCl
Soluble in dil ammonia Insoluble in dil. HNO3
(b) Test – 2
Sample + Potassium dichromate + conc. H2SO4 in test tube
Filter paper moisture with dil. Soln diphenyl carbazide soln placed over test tube
Paper turns violet – red

24. • STANDARD: < 99.5% of NH4Cl with reference to subs dried over silica gel.
• ASSAY
Indirect Acid-base Titration (Acidimetry – Alkalimetry)
Aqu soln of subs treated with neutralized formaldehyde soln
Results in liberation of HCl equivalent to ammonium chloride
This, then titrated with std soln of NaOH using phenolphthalein (indicator)
End point is pale pink colour

25. Modified Volhard’s Method (IP ’66)
Soln of subs acidified with HNO3
Shaken with measured vol. of N/10 silver nitrate
Nitrobenzene previously added to coagulate ppt of AgCl so it will not interfere with titration
4NH4Cl + 4H2O 4NH4OH 4HCl
+
4NH4OH 6HCHO (CH2)6N4
10H2O
+ +
hexamine
4HCl 4NaOH 4NaCl 4H2O
+ +

26. Excess of silver nitrate determined by titration with N/10 ammonium thiocyanate
Using ferric ammonium sulphate as indicator
End point – red colour due to ferric thiocyanate
AgNO3 NH4Cl AgCl NH4NO3
AgNO3 NH4SCN AgSCN NH4NO3
FeNH4(SO4)2 3NH4SCN Fe(SCN)3 2(NH4)2SO4
+
+
+
+
+
+
Ferric thiocyanate

27. • STORAGE: NH4Cl is slightly hygroscopic, it is stored in a well closed container.
• MEDICINAL USES
 Expectorant
 Diuretic
 Systemic acidifier
 Treatment of metabolic alkalosis
 To maintain urine at acid pH in treatment of some urinary-tract disorders

28. THANK YOU…
“Chemistry is the study of
Transformation….”