limit test definition and all limit tests

• Lead is an undesirable and harmful substance
present in pharmaceutical substances.
• Limit test for Lead can be performed by two
methods.
1) I.P or U.S.P method
2) B.P method

Limit test for lead according to B.P method:
• According to B.P method, Limit test for lead is performed in Nessler cylinders.
• Limit test for lead is based on the reaction between lead present in the sample
with sodium sulphide to form lead sulphide with brown colouration.
Pb(NO3)2 + Na2S → PbS + 2NaNO3
( Lead Sulphide )
• The intensity of the colour depends on the amount of lead present in the
sample.
• When a little amount of lead is present in the sample as impurity, brown colour
is formed.
• When a large amount of lead is present in the sample as impurity, brownish
black precipitate is formed.
• The intensity of the colour produced by the sample is compared with that of the
standard.

Preparation of Primary solution and Auxiliary
solution
• To perform limit test for lead according to B.P.
method, two solutions are to be prepared.
1. Primary solution
2. Auxiliary solution
• Primary solution contains a definite amount but
greater amount of sample than the auxiliary solution.
• Auxiliary solution contains a definite amount of
sample and a definite amount of standard solution
(Lead nitrate).

Primary solution Auxiliary solution
Dissolve a specified amount of sample [2gm]
in 20 ml of water containing 10 ml of
acetic acid.
Dissolve a specified amount of sample [1gm]
in 20 ml of water containing 7 ml of acetic
acid.
Add 2ml of lead nitrate solution.
Add 10 ml NH3 and 1ml KCN solution. Add 10 ml NH3 and 1ml KCN solution.
Observe the color. If there is any difference
in color then add burnt
sugar.
Observe the color. If there is any difference in
color then add burnt sugar.
Note: More amount of burnt sugar is added to the solution
having less intensity of colour, to correct the colour difference.
Makeup the volume to 50 ml with distilled
water
Makeup the volume to 50 ml with distilled
water.
If the solution is turbid, filter the solution and
once again makeup the volume to 50 ml with
distilled water.
If the solution is turbid, filter the solution and
once again makeup the volume to 50 ml with
distilled water.
Add 2 drops of sodium sulphide[Na2S] solution. Add 2 drops of sodium sulphide[Na2S] solution.
Stir with a glass rod and allow to stand for 5
minutes for the development of colour.
Stir with a glass rod and allow to stand for 5
minutes for the development of colour.

• Observation:
• If the intensity of the colour produced by the
primary solution is less than that of the
auxiliary solution then the sample passes the
limit test for lead.
• If the intensity of the colour produced by the
primary solution is more than that of the
auxiliary solution then the sample fails the limit
test for lead.

Limit test for lead according to
I.P. or U.S.P. method :
• Limit test for lead according to
I.P. or U.S.P. method is based on the extraction of lead by
solutions of dithizone.
• Lead present as an impurity in the substances, is separated by
extracting an alkaline solution with dithizone extraction
solution.
• According to this method the test is performed in separating
funnels.
• This test is based on the reaction between lead and dithizone
in chloroform to form lead dithizone complex, which is violet
in color. This test is performed under alkaline conditions[NH3].

• The principle involved in the limit test for lead
includes the reaction between lead present in the
sample and dithizone [diphenyl thiocarbazone] to
form lead dithizone complex which shows violet
colour.
• Dithizone in chloroform [CHCl3] is able to extract lead
from alkaline aqueous solutions as lead dithizone
complex.
• Dithizone is having green colour in chloroform and the
lead dithizone complex is having violet colour.

• The intensity of the colour of lead dithizone
complex depends on the amount of lead
present in the sample solution.
• In this method the interference and influence
of other metal ions can be eliminated by
adjusting the optimum pH for the extraction
by employing ammonium citrate, potassium
cyanide and hydroxyl amine HCl reagents.

• PROCEDURE:
• Transfer a specified volume of sample solution into a separating
funnel.
• To this add 6ml ammonium citrate solution, 2ml potassium cyanide
solution and 2ml hydroxyl amine HCl solution. This is followed by the
addition of 2 drops of phenol red indicator.
• Add ammonia until the solution turns red (to make the solution
alkaline).
• To the resulting solution add 5ml dithizone solution for extraction
and shake the solution for 15 sec.
• Now transfer the chloroform layer into another separating funnel.
• Repeat the extraction for 3 more times.

• Mix the collected chloroform extracts well by shaking
for 30 sec with 20ml 1% nitric acid solution and discard
the chloroform layer.
• With small volumes of chloroform (2 ml) wash the acid
solution several times to completely remove dithizone.
• To the resulting acidic solution, now add 5ml standard
dithizone solution and shake for 30 sec.
• Now the violet colour produced in the chloroform
layer is compared with that of the standard prepared in
the same manner using standard lead nitrate solution.

limit test definition and all limit tests

Sources of impurities
• A compound is said to be pure if it is free from impurities.
• A compound is said to be impure if it is having impurities.
• Purity means freedom from impurities.
• Impurity is an undesirable foreign substance present in the
pharmaceutical substances. It may be toxic or non toxic.
• Types of inorganic impurities:
o Chlorides
o Sulphates
o Iron
o Arsenic
o Lead and
o Heavy metals

Sources of impurities
1. Raw materials employed in manufacture
2. Reagents used in manufacturing process
3. Intermediate products in the manufacturing process
4. Defects in the manufacturing process
5. Solvents employed in the manufacture
6. Action of raw materials, solvents and reagents on the reaction
vessels
7. Atmospheric contamination
8. Storage conditions
9. Decomposition
10. Adulteration / Substitution

• The term Pharmacopoeia comes from the Greek
words “Pharmakon” meaning ‘drug’ and ‘Poiein’
meaning ‘make’.
• Pharmacopoeia is a book containing directions for the
identification of compound medicines, and published
by the authority of a government or a medical
or pharmaceutical society.
• Descriptions of preparations are called monographs.
• In a broader sense it is a reference work for
pharmaceutical drug specifications.

List of National Pharmacopoeias
• Indian Pharmacopoeia
• British Pharmacopoeia
• Chinese Pharmacopoeia
• European Pharmacopoeia
• French Pharmacopoeia
• German Pharmacopoeia
• United States Pharmacopeia

Editions of I.P.
Edition Year Addendum/Supplement
1st Edition 1955 Supplement 1960
2nd Edition 1966 Supplement 1975
3rd Edition 1985
Addendum 1989
Addendum 1991
4th Edition 1996
Addendum 2000
Vet Supplement 2000
Addendum 2002
Addendum 2005
5th Edition 2007 Addendum 2008
6th Edition 2010 Addendum 2012
7th Edition 2014
Addendum 2015
Addendum 2016
8th Edition 2018

• Principle:
• Arsenic is an undesirable and harmful impurity present in
pharmaceutical substances.
• Even though there are many qualitative and quantitative methods for
the determination of arsenic, the Pharmacopoeial method is based on
Gutzeit test.
• In this test arsenic present in the sample is converted to arsine gas
( AsH3 ) with the help of various reagents.
• When this arsine gas is passed over a mercuric chloride paper, it
produces yellow stain on the paper.
• The intensity and depth of the stain produced depends on the amount
of arsenic present in the sample.

• In the similar manner, a standard stain is produced
from a definite amount of arsenic trioxide.
• Compare the intensity of stain produced by the
sample with that of the standard.
• If the intensity of the stain produced by the sample is
less than that of the standard then the sample passes
the limit test for arsenic.
• If the intensity of the stain produced by the sample is
more than that of the standard then the sample fails
the limit test for arsenic.

• The chemical reactions involved in the conversion of
arsenic present in the sample to arsine gas includes the
following steps.
• When the sample is dissolved in acid or when the
aqueous solution of the sample is acidified with HCl,
arsenic present in the sample is converted to arsenic
acid or arseneous acid depending upon the valency
state of the arsenic in the sample.
As 5+
→ H3AsO4 (arsenic acid)
As 3+
→ H3AsO3 (arseneous acid)

• If arsenic acid is formed, it is reduced to arseneous
acid in the presence of KI and SnCl2.
H3AsO4 → H3AsO3
• Arseneous acid thus obtained is reduced to arsine
gas by nascent hydrogen, which is obtained from zinc
and stannated HCl.
H3AsO3 + 6H → AsH3 + 3H2O
• When this arsine gas is passed over a mercuric
chloride paper, it produces yellow stain on the paper.

• Apparatus:
• The apparatus used to perform limit test for arsenic consists of a wide
mouth bottle of 120 ml capacity.
• It is fitted with a rubber bung, carrying a glass tube of 200 mm long and 6.5
mm internal diameter.
• The glass tube consists of a hole of 2 mm at one end.
• The other end of the glass tube is smooth and it carries two rubber bungs.
• A mercuric chloride paper is sandwiched between the two rubber bungs.
• The two rubber bungs are held in place by means of a clip.
• The glass tube is packed with cotton wool, which is previously moistened
with lead acetate solution.
• Lead acetate cotton plug is used to trap H2S gas which may be evolved
along with arsine gas.

• Procedure:
• The reagents used in the limit test for arsenic includes KI, Zn,
HCl, SnCl2 … etc.
• All the reagents should be arsenic free and are designated as
“AsT”.
• Sample solution is prepared as specified in I.P. and the
solution is placed in the wide mouth bottle.
• After adding all the reagents into the wide mouth bottle, the
glass tube is prepared and is placed quickly in position.
• Now the complete action is allowed to proceed for 40
minutes.

• A standard stain is produced by taking a definite amount of arsenic
trioxide under similar experimental conditions.
• Compare the intensity of stain produced by the sample with that
of the standard.
• Comparison should be done in day light.
• As the stain produced on the mercuric chloride paper fades on
keeping, comparison should be done immediately.
• If the intensity of the stain produced by the sample is less than
that of the standard then the sample passes the limit test for
arsenic.
• If the intensity of the stain produced by the sample is more than
that of the standard then the sample fails the limit test for arsenic.

• Principle:
• Limit test for Iron is based on the reaction between iron
present in the sample with thioglycolic acid under alkaline
conditions in presence of citric acid to form a pale pink to
deep reddish purple coloured ferrous thioglycolate complex.
• Citric acid is useful to prevent the interference of other metal
cations present in the reaction.
• Thioglycolic acid reduces Fe3+
to Fe2+
and forms a complex
with Fe2+
.
• Ferrous thioglycolate is colourless in acid or neutral solutions.
The colour is developed only in the presence of alkali.

Procedure:
• Preparation of Test solution:
• Dissolve a specified amount of sample (1g) in 40 ml
distilled water in a Nessler cylinder.
• Add 2 ml of 20 % w/v of citric acid sloution.
• Add 2 drops of thioglycollic acid.
• Add ammonia to make the solution alkaline.
• Make up the volume to 50 ml with distilled water.
• Stir with a glass rod and keep it aside for 5 min.
• Color developed is viewed vertically and compared with
standard solution.

• Preparation of Standard solution:
• Transfer 2 ml of standard iron solution (20 µg/ml)
into a Nessler cylinder.
• Add 2 ml of 20 % w/v of citric acid sloution.
• Add 2 drops of thioglycollic acid.
• Add ammonia to make the solution alkaline.
• Make up the volume to 50 ml with distilled water.
• Stir with a glass rod and keep it aside for 5 min.

• Observation:
• The purple colour produced in the sample solution
should not be greater than that of the standard
solution.
• If the colour intensity produced in the test is less than
that of the standard, the sample will pass the limit
test for iron.
• If the colour intensity produced in the test is more
than that of the standard, the sample will fail the limit
test for iron.

Combinations of antacids
• It is well known that no antacid is available in the market
which satisfies the requirements of an ideal antacid.
• Calcium and aluminium compounds may cause
constipation, where as magnesium compounds may
produce laxative effect.
• However, many preparations which are having
combination of antacids are being marketed.
• The idea behind such combination is to counteract the
constipative action of calcium and aluminium containing
antacids with laxative effect of magnesium containing
antacid.

Preparations containing combination of antacids are
preferred for the following reasons:
• To achieve quick and prolonged effect.
• Neutralizing the side effects.
• Additive effect.
• Gastric emptying.
• To compensate the constipative effect of calcium and
aluminium with the laxative effect of magnesium.
• To have long duration of action with rapid onset of
action.

• Examples for combination antacid preparations:
• Aluminium hydroxide-Magnesium carbonate co-dried gel :
• It is a co-precipitate of aluminium hydroxide and magnesium carbonate. It acts
as an antacid that is given in doses of up to 1g.
• Algicon tablets :
• The tablets are chewable, prepared by aluminium hydroxide-magnesium
carbonate co-dried gel, magnesium alginate, magnesium carbonate and
potassium bicarbonate.
• The combination is also available as suspension.
• It acts as antacid.
• Simeco tablets:
• These tablets contain aluminium hydroxide-magnesium carbonate co-dried gel,
magnesium hydroxide, and activated dimethicone.

• Aluminium hydroxide gel-Magnesium trisilicate combination:
• This combination contains Aluminium hydroxide and Magnesium trisilicate.
• This is one of the most common combinations.
• It also has laxative and protective effect.
• Magaldrate :
• It is a chemical combination of aluminium hydroxide and magnesium hydroxide.
• It occurs as white, odourless, crystalline powder which is insoluble in water and alcohol, but
soluble in dilute solutions of mineral acids.
• Calcium carbonate containing antacid mixtures :
• Calcium carbonate with aluminium hydroxide gel yields products which have rapid and
prolonged action.
• Three part combinations of calcium carbonate, aluminium hydroxide gel and a magnesium
containging antacids are also available.

• Alginic acid-sodium bicarbonate containing antacid mixture :
• This combination is available as chewable tablet.
• The alginic acid reacts with sodium bicarbonate, forming
sodium alginate and carbon dioxide.
• Gelusil:
• It is available in the form of tablets and oral liquid.
• It mainly contains dried aluminium hydroxide gel, magnesium
hydroxide and activated dimethicone.

Expectorants
• Definition:
• Expectorant is a drug that promotes the
secretion, liquefaction, or expulsion of sputum
from the respiratory passages. It is used to
treat cough.
• Ex: Ammonium chloride, Potassium iodide.

AMMONIUM CHLORIDE*
• Mol. Formula: NH4Cl
• Mol.Wt. : 53.5
• Medicinal uses:
• Expectorant; diuretic; systemic acidifier; acid-base regulator.
• Preparation:
• Commercial preparation: Ammonium chloride is commercially prepared by
neutralizing hydrochloric acid with ammonia. The resulting solution is
evaporated to dryness to get crystals of Ammonium chloride.
NH3 + HCl → NH4Cl
• From ammonium sulphate: Ammonium chloride is also prepared by heating
ammonium sulphate with sodium chloride.
(NH4)2SO4 + 2 NaCl → 2 NH3 + 2 HCl + Na2SO4
NH3 + HCl → NH4Cl

• Properties:
• It occurs as colourless crystals or a white, crystalline
powder.
• It is soluble in water.
• On heating Ammonium chloride is decomposed to
ammonia and hydrogen chloride gas.
NH4Cl → NH3 + HCl
• Ammonium chloride reacts with base (NaOH) to release
ammonia gas.
NH4Cl + NaOH → NH3 + NaCl + H2O

• Tests for purity:
• Ammonium chloride should be tested for pH (4.5 to 6.0,
determined in a 5.0 per cent solution), sulphates, iron,
arsenic, heavy metals, loss on drying.
• Assay:
• Weigh accurately about 0.1 g, dissolve in 20 ml of water and
add a mixture of 5 ml of formaldehyde solution, previously
neutralised to phenolphthalein solution, and 20 ml of water.
• After 2 minutes, titrate slowly with 0.1 M sodium hydroxide
using 2-3 drops of phenolphthalein solution as indicator.

POTASSIUM IODIDE
• Molecular Formula : KI
• Medicinal Uses :
– Expectorant,
– Antithyroid,
– Antifungal
• Preparation : Potassium Iodide is prepared by treating a hot
solution of potassium hydroxide with iodine to form a mixture of
potassium iodide and potassium iodate.
6 KOH + 3 I2 → 5KI + KIO3 + 3H2O
• The solution is then concentrated and treated with charcoal
powder to reduce potassium iodate to potassium iodide.
KIO3 + 3C → KI + 3CO

• Properties:
• It occurs as white, crystalline powder.
• It is odourless.
• It has saline and bitter taste.
• It is easily oxidised to iodine by powerful oxidising agents
such as chlorine.
2 KI + Cl2 → 2 KCl + I2
• Tests For Purity:
• Sulphates, Iron, Arsenic, Heavy metals and Potassium iodate.

• Assay :
• Weigh accurately about 0.35 g of KI, dissolve in about
10 ml of water, add 35 ml of hydrochloric acid and 5 ml
of chloroform.
• Titrate with 0.05 M Potassium iodate until the purple
colour of iodine disappears from the chloroform.
• Allow to stand for 5 minutes.
• If any colour develops in the chloroform layer continue
the titration until the chloroform is decolorised.

CATHARTICS
• Cathartics are the drugs that relieve constipation
& promote defecation. These are also known as
laxatives (or) purgatives.
• Based on the mechanism of action cathartics are
classified into 4 types.
1) Stimulants
2) Bulk purgatives
3) Lubricants
4) Saline cathartics

• Stimulants:
• These are the drugs (or) chemicals which act by local irritation on
intestinal tract & bring about stimulation of peristaltic activity. As
they act directly on intestine & stimulate peristalsis they are
known as stimulants.
• Eg:- castor oil, senna, aloe vera...etc.
• Bulk purgatives:
• These are the agents which are able to increase bulk of intestinal
contents. These are cellulose (or) non-digestable type of materials
which swell considerably when wet & stimulate peristalsis.
• Eg:- methyl cellulose, sodium carboxy methyl cellulose...etc.

• Lubricants:
• In constipation, contents of intestine become hard because of
absorption of water by body, there results difficulty in clearing of
bowels. Substances such as liquid paraffin, glycerine act as
lubricants & cause smooth clearance of the faecal matter.
• Saline cathartics:
• Saline cathartics are water soluble drugs & they are taken with
plenty of water. These drugs act by increasing the osmotic load of
the intestine by absorbing large quantity of water and there by
stimulate peristalsis. Thus they quicken & increase evacuation
from the bowel.
• Eg:- Magnesium sulphate, Sodium orthophosphate.

Magnesium sulphate
• Synonym: Epsom salt
• Mol. Formula: MgSO4.7H2O
• Medicinal Uses:
o Osmotic laxative;
o Saline cathartic;
o Used in the treatment of electrolyte deficiency.
• Preparation:
1) Magnesium sulphate is prepared by the action of dilute sulphuric acid on
magnesium carbonate.
MgCO3 + H2SO4 → MgSO4 + H2O + CO2
2) Magnesium sulphate is prepared by the action of dilute sulphuric acid on
magnesium oxide.
MgO+ H2SO4 → MgSO4 + H2O

• Properties:
• Magnesium sulphate occurs as colourless crystals (or) a white crystalline powder.
• It has saline taste.
• When heated gently it looses some of the water molecules and produce
monohydrate.
MgSO4.7H2O → MgSO4.H2O + 6H2O
• But when heated upto 200o
C it produces anhydrous magnesium sulphate by total
loss of water molecules.
MgSO4.7H2O → MgSO4 + 7H2O
• Tests for Purity:
• Chlorides , Iron , Arsenic , Heavy metals , Appearance of solution, Acidity or
Alkalinity and Loss on drying.

• Assay:
• It can be assayed by complexometric titration.
• Weigh accurately about 0.3 g of sample &
dissolve in 50ml distilled water.
• Add 10ml of ammonia-ammonium chloride
buffer solution & titrate the contents with
0.05 M disodium EDTA using mordant black-II
as indicator, until a blue colour is obtained.

Sodium orthophosphate
• Synonym: sodium phosphate / Tri sodium orthophosphate
• Mol. Formula: Na3PO4
• Medicinal use:
• It is used as laxative.
• It is used as cathartic.
• It is used as food additive.
• Preparation:
• It is produced by adding sodium carbonate to a hot solution of
phosphoric acid. The solution is neutralized with sodium hydroxide and
concentrated to get crystals of sodium orthophosphate.
H3PO4 + Na2CO3 → Na2HPO4 + H2O + CO2
Na2HPO4 + NaOH → Na3PO4 + H2O

• Properties:
• It occurs as white crystalline powder.
• Its solution is alkaline in nature.
• It reacts with barium chloride to produce barium
orthophosphate and sodium chloride.
2Na3PO4 + 3BaCl2 → Ba3(PO4)2 + 6NaCl
• Chlorides , Iron , Arsenic , Heavy metals , Appearance of
solution, Acidity or Alkalinity and Loss on drying.

• Assay:
• It can be assayed by acid-base titration.
• Weigh accurately about 0.5 g of sample and
dissolve in 50ml distilled water.
• Titrate the contents with 0.5N sulphuric acid
using Bromocresol green as indicator.

• ADSORBENT:
• Adsorbents are chemically inert substances which are
used in the treatment of mild diarrhoea or dysentery
or other disturbances of gastro intestinal tract
because of the ability to adsorb gases, toxins and
bacteria.
• They also form a protective coat on the mucosal
membrane and provide mechanical protection. Hence
they are also known as protectives.
• Eg: Kaolin.

Heavy kaolin:
• Medicinal uses:
• It is used as adsorbent in the treatment of diarrhoea or dysentery.
• It is used as Pharmaceutical aid.
• Preparation:
• Heavy kaolin is a purified, natural, hydrated aluminium silicate of variable composition.
• It can be prepared from natural clay.
• Description:
• It is a fine, white or greyish white, soft powder.
• It is odourless, almost tasteless.
• It is insoluble in water.
• Chlorides, Sulphates, Arsenic, Heavy metals, Adsorption power, Acidity or alkalinity and
Organic impurities.

Light kaolin:
• Medicinal uses:
• Preparation:
• Light Kaolin is a native hydrated aluminium silicate, freed from most of its impurities by
elutriation and dried. It may contain a suitable dispersing agent.
• It can be prepared from natural clay.
• Description:
• It is a light white powder.
• It should be free from gritty particles.
• It is odour less, almost tasteless.
• It is unctuous to the touch.
• Chlorides, Arsenic, Heavy metals and Loss on drying.

• SUSPENDING AGENTS:
• Suspending agents are also known as thickening agents.
• Suspending agents are inert substances which are added to a liquid containing an insoluble
medicament to ensure that the medicament is uniformly distributed.
• Eg: Bentonite
• Molecular formula: Al2O3. 4SiO2. H2O
• Uses:
• It is used as suspending agent.
• It is an ingredient of calamine lotion.
• It is used as an emulsifying agent.
• It is used as a base for many pharmaceutical preparations.
• It can also be used as laxative.
• Preparation:
• Bentonite is a natural, colloidal, hydrated aluminium silicate that has been processed to remove grit
and non-swelling components of the ore.
• It can be prepared from naturally occuring sources.

• Properties:
• It occurs as very fine, pale buff or cream-coloured to greyish-white
powder.
• It is free or almost free from gritty particles.
• It’s aqueous suspension is alkaline in nature.
• Swelling of bentonite takes place when added to water.
• pH : 9.0 to 10.5, determined in a 2.0 per cent w/v suspension in water.
• Heavy metals, Swelling power, Coarse particles, Microbial
contamination, Loss on drying.

• EMETICS:
• Emetics are the drugs which promote forced
regurgitation by which the contents of the
stomach get expelled through the oral cavity.
• Ex: Copper sulphate, Sodium potassium
tartarate

Copper Sulphate
• Synonym: Cupric Sulphate
• Molecular formula: CuSO4.5H2O
• Medicinal Uses:
• It is used as emetic.
• Preparation:
• It is prepared by treating granulated copper
with sulphuric acid in presence of air.
2 Cu + 2 H2SO4 + O2 → 2 CuSO4 + 2 H2O

• Properties:
• It occurs as blue crystalline powder.
• It is freely soluble in water.
• It’s aqueous solution is acidic in nature.
• At higher temperatures, it decomposes into sulphur dioxide,
oxygen and black cupric oxide.
2 CuSO4 → 2 CuO + 2 SO2 + O2
• Test For Purity:
• Chlorides, Iron, Arsenic, Lead and Heavy metals.

• Assay:
• It is assayed by redox titration.
• Dissolve 0.2 grams of sample in 50 ml water.
• Add 2 ml sulphuric acid and 3 grams of potassium
iodide.
• Keep it aside for 5 minutes.
• Titrate the liberated iodine with 0.1 N sodium
thiosulphate using starch solution as indicator
towards the end of the titration.

Sodium potassium tartarate
• Synonym: Rochelle salt
• Molecular formula: C4H4O6Na K 4H2O
• Medicinal uses:
• It is used as emetic.
• It is used as cathartic .
• It is used as laxative.
• Preparation:
• Sodium potassium tartarate is prepared by neutralizing a
solution of sodium bicarbonate with potassium bitartarate.
NaHCO3 + K H C4H4O6 → C4H4O6 Na K + H2O + CO2

• Properties:
• It occurs as colorless crystals (or) white crystalline powder.
• It is decomposed by acetic acid to give potassium bitartarate.
C4H4O6 Na K + CH3COOH → C4H4O6 K H + CH3COONa
• Test For Purity:
• Chlorides, Sulphates, Iron, Arsenic, Lead and Heavy metals.

• Assay:
• It is assayed by acid-base titration.
• Weigh accurately a specified amount of sample and
heat in a crucible.
• Boil the residue with a mixture of 50 ml water and 15 ml
0.5N sulphuric acid.
• Filter the solution and wash the residue with water.
• Titrate the filtrate and washings for excess acid with
0.5N sodium hydroxide used methyl orange as indicator.

HAEMATINICS
• Haematinics are the substances which
increase the haemoglobin content of the
blood and thus raises the quality of blood.
• Generally, iron and it’s preparations are
known as haematinics.
• They are used to treat anemia.
• Ex: Ferrous sulphate, Ferrous gluconate.

Ferrous sulphate
• Molecular formula: FeSO4 7H20
• Mol. Wt. : 278
• Medicinal Uses:
• It is used as haematinic to treat iron deficiency.
• Preparation:
• Ferrous sulphate is prepared by dissolving iron in excess of
dilute sulphuric acid. The liquid is filtered and
concentrated to get bluish green crystals of ferrous
sulphate.
Fe + H2SO4 → FeSO4 + H2

• Properties:
• It occurs as bluish green crystals.
• It has astringent taste.
• It is efflorescent in air.
• On exposure to moist air, the crystals rapidly oxidise and become
brown.
• On heating, it decomposes into ferric oxide, sulphur dioxide and
sulphuric acid.
2 FeSO4 7H20 → Fe2O3 + SO2 + H2SO4 + 6 H20

• pH : 3.0 to 4.0, determined in a 5.0 per cent
solution.
• Chlorides,
• Arsenic,
• Lead and
• Heavy metals.

• Assay:
• It can be assayed by redox titration.
• Method-1:
• Weigh accurately about 0.5gm of sample, dissolve in 50 ml
distilled water. Add 10 ml dilute H2SO4 and titrate the contents
with 0.1N potassium permanganate until pink colour appears.
• Method-2:
• Weigh accurately about 0.5gm of sample dissolve in 50ml
water. Add 10ml dilute H2SO4 and titrate the contents with
0.1N cerric ammonium sulphate using ferroin as indicator. End
point is appearance of blue colour.

Ferrous Gluconate
• Molecular formula: C12H22O14Fe.2H2O
• Medicinal Uses:
• It is used as haematinic to treat iron deficiency.
• Preparation:
• It can be prepared from glucose.
• Glucose on oxidation in presence of dilute nitric acid produces gluconic
acid.
• Barium carbonate converts gluconic acid to barium gluconate.
• Barium gluconate is treated with ferrous sulphate to get ferrous gluconate
and barium sulphate precipitate.
• By filteration, barium sulphate is removed and the solution is concentrated
to get crystals of ferrous gluconate.

• Properties:
• It occurs as yellowish grey powder.
• It has odour of burnt sugar.
• When it is exposed to air Fe2+
gets oxidized to
Fe3+

• Chlorides,
• Sulphates,
• Arsenic,
• Heavy metals and
• Barium
• Assay:
• Dissolve 0.5 g of sodium bicarbonate in a mixture of 70 ml of water and 30
ml of 1 M sulphuric acid.
• When effervescence ceases, add about 1 g of ferrous gluconate, shake gently
to dissolve and titrate with 0.1 M cerric ammonium nitrate, using few drops
of ferroin solution as indicator, until the red colour disappears.

ANTI MICROBIAL AGENTS
• Anti microbial agent is an agent that kills micro
organisms or stops their growth.
• Anti microbial agents interfere with the growth and
reproduction of causative organisms like bacteria,
fungi, virus, parasites…etc.
• The agents may be antimicrobial agents, antifungal
agents, antiviral agents and antiparasitic agents.
• Examples: Potassium permanganate, Boric acid,
Hydrogen peroxide, Chlorinated lime, Iodine and its
preparations.

Potassium permanganate
• Molecular formula: KMnO4.
• Medicinal uses :
– Antiseptic.
– It is used as anti infective agent.
• Preparation:
• Commercially potassium permanganate is prepared by mixing a solution of
potassium hydroxide with powdered manganese oxide and potassium chlorate.
6KOH + 3MnO2 +KClO3 > 3K2MnO4 + KCl + 3 H2O
• The potassium manganate so formed is boiled with large quantity of water and a
current of chlorine or carbondioxide or ozonised air is passed into the liquid until
it is converted into potassium permanganate.
6K2MnO4 + 3 Cl2 > 6KMnO4 + 6 KCl

• Properties :
• It occurs in the form of dark purple coloured prisms.
• It is a powerful oxidizing agent.
• At high temperatures it gets decomposed to give potassium
manganate.
2KMnO4 > K2MnO4 + MnO2+ O2
• Test for Purity:
– Chlorides
– Sulphates
– Water insoluble matter.

• Assay:
• It can be assayed by Redox Titration.
• Weigh accurately about 0.3 g of sample and
dissolve in sufficient water to produce 100 ml.
• To 20 ml of this solution add 20 ml of water, 1 g of
potassium iodide and 10 ml of 2 M hydrochloric
acid and titrate the liberated iodine with 0.1 M
sodium thiosulphate using starch solution, added
towards the end of the titration, as indicator.

Boric acid
• Synonym: Boracic acid
• Molecular Formula: H3BO3
• Medicinal Uses:
• It is used as anti infective agent.
• It is used as antiseptic for minor burns and cuts.
• It's dilute solution is applied as eye wash.
• Preparation:
1) Medicinal grade boric acid is prepared by treating borax with hydrochloric acid.
Na2B4O7 .10 H2O + 2 HCl > 4H3BO3 + 2 NaCl + 5 H2O
2) In laboratory, boric acid is prepared by adding a mixture of conc. Sulphuric acid
and water to a boiling solution of borax.
Na2B4O7 + H2SO4 + H2O > 4 H3BO3 + Na2SO4

• Properties:
• It is odurless.
• It has bitter taste.
• It is a weak acid.
• It is stable in air.
• When heated, boric acid yields dehydration products.
H3BO3 -------100°C -------> HBO2 + H2O
meta boric acid
4HBO2 ------- 160°C > H2B4O7 + H2O
Tetraboric acid
H2B4O7
>
160°C > 2B2O3 + H2O
Boran trioxide.

– Sulphates
– Arsenic
– Heavy metals
– Loss on drying
• Assay:
• Boric acid is assayed by acid -base titration.
• Weigh accurately about 2 g, dissolve in a mixture of 50 ml of
water and 100 ml of glycerin, previously neutralised to
phenolphthalein solution.
• Titrate the contents with 1 M sodium hydroxide using
phenolphthalein solution as indicator.

Hydrogen peroxide
• Molecular Formula: H2O2
• Medicinal Uses:
• It is used as anti infective agent.
• It has germicidal action.
• It is used for cleaning cuts and wounds.
• Description:
• Hydrogen peroxide solution is an aqueous solution of hydrogen peroxide.
• It is available as
Dilute hydrogen peroxide solution (20 volumes ).
Strong hydrogen peroxide solution (100 volumes).
• Dil. hydrogen peroxide solution contains 6 % w
/w of hydrogen peroxide where
as strong hydrogen peroxide solution contains 27 % w
/w of hydrogen peroxide.

• Preparation:
1. Hydrogen peroxide is prepared by adding a paste
of barium peroxide to ice cold dil. sulphuric acid.
BaO2 + H2SO4 > H2O2 + BaSO4
2. Hydrogen peroxide is prepared by adding a
paste of sodium peroxide to ice cold
dil.sulphuric acid.
Na2O2 + H2SO4 > H2O2 +Na2SO4.

• Properties:
• It is a clear colourless liquid.
• It has acidic taste.
• On decomposition it gives water and oxygen.
2H2O2 > 2H2O + O2
• Acidity
• Non-volatile matter
• Organic stabilisers

• Assay:
• Dilute about 10 ml to 100 ml with water.
• To 10 ml of the resulting solution add 20 ml of
1 M sulphuric acid and titrate the contents
with 0.02 M potassium permanganate.

Chlorinated lime
• Synonym: Bleaching powder.
• Molecular formula: CaOCl2.H2O/Ca(OCl)Cl.H2O
• Medicinal Uses:
• It is mainly used for its disinfecting and bleaching properties.
• It is commonly employed in the chlorination of water.
• It is useful in the treatment of swimming tank.
• Preparation:
• It is obtained by the action of chlorine gas on calcium
hydroxide.
Ca(OH)2 + Cl2 > Ca(OCl)Cl + H2O

• Properties:
• It occurs as dull white powder.
• It has characteristic odour.
• It is sparingly soluble in water.
• On exposure to air it absorbs moisture and decomposes by
liberating chlorine.
– Sulphates
– Arsenic
– Heavy metals
– Loss on drying

• Assay:
• It is assayed by redox titration.
• An aqueous suspension of the sample is treated
with acetic acid in presence of potassium iodide
in an iodine flask.
• Keep it a side for 5min.
• Titrate the liberated iodine with 0.1N sodium thio
sulphate using starch solution as indicator, added
towards the end point of the titration.

Iodine
• Molecular formula : I2
• Medicinal Uses:
• Antiseptic
• It is used as disinfectant.
• It is used as germicide.
• It is used as counter irritant.
• It plays an important role for proper thyroid
functioning.

• Preparation:
• It can be prepared from "sea weeds".
• Laminaria digitata is a sea weed.
• The ash of this sea weed is known as 'kelp'.
• Kelp is extracted with water and the aqueous extract is
concentrated and crystallised to separate sulphates and
chlorides of sodium and potassium.
• By adding sulphuric acid small amounts of sulphites and
thiosuphates can be decomposed. As a result sulphur is
precipitated and is separated.

• Now the acidic solution contains soluble iodides and
small amounts of bromides and chlorides. This solution
is treated with chlorine to precipitate iodine. The
precipitated iodine is collected and purified.
• The collected iodine mainly contains iodine mono
chloride, and iodine mono bromide. It is treated with
potassium iodide to get potassium chloride and
potassium bromide with the production of iodine.
ICl + KI > KCl + I2
IBr + KI > KBr + I2

• Properties:
• It occurs as heavy, bluish black, rhombic prisms.
• It has characteristic odour.
• At ordinary temperature it is volatile in nature.
• It is insoluble in water and soluble in aqueous solution of
potassium iodide.
• It is a powerful oxidising agent.
• Aqueous solution of iodine reacts with reducing agents
like sodium thiosulphate to oxidise them.
I2 + 2 Na2S2O3 > Na2S4O6 + 2 NaI

• Bromides and chlorides
• Non-volatile matter
• Assay:
• Weigh accurately about 0.2 g, transfer to a flask
containing 1 g of potassium iodide and 20 ml of water.
• Add 1ml of 2 M acetic acid, dissolve completely and add
50 ml of water.
• Titrate the contents with 0.1 M sodium thiosulphate
using starch solution as indicator.

SOLUTIONS OF IODINE
• AQUEOUS IODINE SOLUTION:
• Synonym:- Lugol's solution
• Aqueous iodine solution contains 5% w/v of
iodine and 10% w/v of potassium iodide in
purified water.
• Medicinal use :-
• It is a good source of iodine
• It possess germicidal and fungicidal properties

• Composition:
• Iodine - 5gms
• Potassium iodide - 10gms
• Purified water - to produce 100ml.
• Preparation:
• Dissolve 10gms of potassium iodide in 50ml of purified water.
• Dissolve 5gms of iodine in the above solution and make up the
volume to produce 100ml with purified water.
• Properties:
• It is a transparent brown liquid.
• It has characteristic odour of iodine.

• WEAK IODINE SOLUTION:
• Synonym: Tincture of iodine
• Weak iodine solution contains 2% w/v of iodine
and 2.5 % w/v of potassium iodide in 50% alcohol.
• Medicinal uses:
• It is a good source of iodine.
• It is a well known antiseptic which is applied on
cuts and wounds.

• Composition:
• Iodine - 2gms
• Potassium iodide - 2.5gms
• Alcohol (50%) - to produce 100ml.
• Preparation:
• Dissolve 2.5 gms of potassium iodide in 50ml alcohol.
• Dissolve 2gms of iodine in the above solution and make up the
volume to produce 100ml with alcohol.
• Properties:

• STRONG IODINE SOLUTION:
• It is having 10% w/v of iodine and 6% w/v of
potassium iodide in purified water and 90%
alcohol.
• Medicinal uses:
• It is a well known antiseptic which is applied on
cuts and wounds.

• Composition:
• Iodine -10gms
• Potassium iodide - 6 gms
• Purified water - to dissolve the contents
• Alcohol (90%) -to produce 100ml.
• Preparation:
• Dissolve 6 gms of potassium iodide in 25 ml purified water.
• Add 10 gms of iodine to the above solution and make up the volume to
produce 100 ml using 90% alcohol.
• Properties:

• POVIDONE – IODINE SOLUTION:
• Povidone (poly vinyl pyrrolidine) – Iodine solution is a solution
of Povidone & Iodine in purified water. It may contain alcohol.
• Povidone – Iodine solution is a complex produced by the
interaction between povidone – and iodine.
• This complex contains about 10 % w/v of iodine.
• Medicinal uses:
• It is a well known antiseptic which is applied on cuts and
wounds.

• Properties:
• It is a deep brown liquid.
• The complex is soluble in water.
• The solution has acidic pH
• Assay:
• It is assayed for Iodine by Redox titration.
• To 10 ml of the solution add 30 ml water and titrate the
contents with 0.1 N sodium thiosulphate using starch
solution as indicator, added towards the end of the titration.

Classification of Anti microbial agents
• Anti microbials can be classified according to
their function.
• 1. Antiseptics
• 2. Disinfectants
• 3. Germicides
• 4. Bacteriostatics
• 5. Sanitizers

• 1. Antiseptics:
• Antiseptics are the substances that are able to kill or prevent the growth of micro
organisms. This term is specific for preparations which are to be applied to living
tissues.
• Antiseptics oppose the sepsis of the damaged tissue by inhibiting the microbial
multiplication and metabolic activities or by killing the pathogenic micro
organisms.
• In general antiseptics are protein denaturants and act on enzymes in the bacteria.
• 2. Disinfectants:
• Disinfectants are the substances that prevent infection by the destruction of
pathogenic micro organisms. This term is specific for preparations which are to be
applied to inanimate objects.
• Disinfectants are widely used for home and hospital sanitation. They are
bactericidal in nature.

• 3. Germicides
• Germicides are the substances which kill micro organisms.
• Based on the exact action they may be antibacterial agents,
antifungal agents, antiviral agents & antiparasitic agents.
• Antibacterial agents: These are used to treat bacterial
infections.
• Antifungal agents: These are used to kill or prevent growth of
fungi.
• Antiviral agents: These are used to treat viral infections.
• Antiparasitic agents: These are used to treat infections caused
by parasites.

• 4. Bacteriostatics
• These are the substances which act by inhibiting
the growth of bacteria. They don’t kill bacteria
but arrest the growth of bacteria.
• 5. Sanitizers
• Sanitation is mainly concerned with cleaning or
washing away organic matter.
• Disinfectants that are used to maintain general
public health standards are known as sanitizers.

Ideal characteristics of antimicrobial agents
• An antimicrobial agent should possess the following characteristics:
 It should possess antiseptic or germicidal activity.
 It should possess rapid onset of action and sustained activity.
 It should possess good therapeutic index, indicating usefulness in
the concentration employed.
 It should possess broad spectrum of antimicrobial activity against
the pathogenic micro organisms.
 It should not cause any cellular damage.
 It should show no systemic toxicity from topical applications.
 It must be soluble in water or other solvent to the extent necessary
for effective use.

Mechanism of Action of Antimicrobials
• Inorganic compounds generally exhibit
antimicrobial action by any one of the
following three mechanisms;
• Oxidation
• Halogenation
• Protein precipitation

• Oxidation: Antimicrobials bring about
oxidation of active functional groups present
in proteins/enzymes vital to the growth (or)
survival of microorganisms.
• Halogenation: Antimicrobials act by liberating
chlorine/iodine. The liberated chlorine/iodine
act on peptide linkage & destruct the proteins;
which leads to death of the micro organisms.

• Protein precipitation: Many metal ions exhibit protein
binding or protein precipitation. When metal-ions
interact with microbial proteins, physical properties of
the protein are usually altered; the protein may be
denatured and precipitation usually occurs. When the
concentration of metal is low, precipitation prevents
deep tissue penetration and astringent action occurs.
When the concentration of metal is high, membrane
and intracellular structures are damaged; which leads
to death of the microorganisms.

ANTIDOTES
• Antidotes are the drugs used in the treatment
of poisoning. They act by neutralizing or
conteracting effects of poision.
• Ex: sodium thiosulphate , sodium nitrite

SODIUM THIOSULPHATE
• Synonym: Sodium Hyposulphite, Hypo
• Molecular Formula: Na2S2O3.5H2O
• Medicinal Uses:
• It is used as antidote.
• It is used as antidote in the treatment of cyanide poisoning.
• Preparation:
1) Sodium Thiosulphate is prepared by boiling aqueous sodium hydroxide and sulphur.
6 NaOH + 4S → 2 Na2S + Na2S2O3 + 3 H2O
2) Sodium Thiosulphate is prepared from soda ash, sulphur dioxide and sulphur.
Na2CO3 + H2O + 2SO2 → 2NaHSO3 + CO2
2NaHSO3 + Na2CO3 → 2Na2SO3 + H2O + CO2
Na2SO3 + S → Na2S2O3

• Properties:
• It occurs as colourless crystalline powder.
• It has alkaline taste.
• It is deliquescent in moist air and effloresces in dry
air at temperature above 33°C.
• It has reducing action on halogens.
2 Na2S2O3 +I2 > 2 NaI + Na2S4O6

• Chlorides
• Sulphates and sulphites
• Sulphides
• Arsenic
• Heavy metals
• Assay:
• Weigh accurately about 0.5 g, dissolve in 20 ml of water and
titrate with 0.05 M iodine using starch solution, added towards
the end of the titration, as indicator.

Activated Charcoal
• Synonym: Decolorising Charcoal
• Medicinal Uses:
• Preparation:
• Activated Charcoal is obtained from vegetable matter by suitable
carbonisation processes intended to confer a high adsorbing power.
• Description:
• It is a light black powder.
• It is from from grittiness.

• Acidity or alkalinity
• Acid-soluble substances
• Ethanol-soluble substances
• Alkali-soluble coloured matter
• Chlorides
• Sulphates
• Heavy metals
• Sulphated ash
• Loss on drying
• Adsorbing power

Sodium Nitrite
• Molecular Formula: NaNO2
• Medicinal Uses:
• It is used as antidote in the treatment of cyanide
poisoning.
• Preparation:
• Sodium nitrite is prepared by treating sodium
hydroxide with a mixture of nitrogen dioxide and
nitric oxide.
2 NaOH + NO2 + NO → 2NaNO2 + H2O

• Properties:
• It occurs as white to slightly yellowish crystalline powder.
• It is hygroscopic in nature.
• Above 330°C, it decomposes to give sodium oxide , nitric
oxide and nitrogen dioxide.
2NaNO2 → Na2O + NO + NO2

• Tests For Purity:
• Chlorides
• Sulphates
• Iron
• Arsenic
• Heavy metals
• Assay:
• Sodium nitrite is assayed by Redox titration.
• Dissolve 1gm of sample in 100ml distlled water.
• Transfer 10ml of the solution into a mixture of 50ml 0.1N potassium
permanganate ,100ml water and 5ml sulphuric acid.
• Warm the solution to 40°C and allow to stand for 5 min.
• Now add 25ml 0.1N oxalic acid solution.
• Heat the mixture to 80°C and titrate the contents with 0.1N potassium permanganate
until the appearance of pale pink colour.

ASTRINGENTS
• Astringents are the compounds which bring about protein precipitation.
• They are usually applied to the damaged skin topically (or) to the mucous
membrane of the gastro intestinal tract. The precipitated protein and the
astringent form a protective layer on the surface.
• Astringents are mainly used:-
• To treat diarrhoea.
• They promote wound healing process.
• They possess deodorant properties.
• They decrease sweating and make the skin tough.
• Examples:- Zinc sulphate,
Potash alum.

Zinc sulphate
• Molecular formula: ZnSO4.7H2O
• Medicinal uses:
• It is used as astringent.
• It is used to treat zinc deficiency condition.
• It is the main ingredient of zinc sulphate eye drops.
• Preparation:
1) Zinc sulphate is prepared by treating zinc metal with diute sulphuric acid. The
liquid is filtered and the resulting filtrate is evaporated to crystallization to get
crystals of zinc sulphate.
Zn + H2SO4 → ZnSO4 + H2
2) Zinc sulphate is prepared by heating zinc sulphide in the presence of air.
ZnS + 2O2 → ZnSO4

• Properties:
• It has astringent and metallic taste.
• It reacts with hydrogen sulphide to form zinc
sulphide precipitate.
ZnSO4 + H2S → ZnS + H2SO4

• Chlorides
• Iron
• Arsenic
• Assay:
• It can be assayed by complexometric titration.
• Weigh accurately about 0.5 g and dissolve in 5 ml of 2M acetic acid
and dilute to 50 ml with water. To the resulting solution add few
drops of xylenol orange indicator and sufficient hexamine to
produce violet-pink colour. Further, add 2 g of hexamine and titrate
with 0.1 M disodium edetate until the colour changes to yellow.

POTASH ALUM
• Synonym:
• Alum,
• Aluminium-potassium sulphate
• Molecular formula: K Al (SO4)2. 12H2O
• Medicinal uses:
• It is used as astringent
• It has antiseptic properties
• It used as pharmaceutical aid
• Preparation:
• Potash alum is prepared by adding a hot con. solution of potassium sulphate
to the equimolar proportion of aluminium sulphate. Then the solution is
concentrated and cooled to get crystals of potash alum.
K2SO4 + Al2(SO4)3 + 12H2O → 2 K Al (SO4)2. 12H2O

• Properties:
• It occurs as colourless crystals.
• It has sweet astringent taste.
• At 200°C it looses it’s water and becomes
anhydrous.
2 K Al (SO4)2. 12H2O → 2 K Al (SO4)2 + 12H2O

• Chlorides
• Iron
• Arsenic
• Heavy metals
• Assay:
• Potash alum can be assayed by complexometric titration.
• Weigh accurately about 0.8 gms of sample and transfer into a 500 ml
beaker. Moisten it with glacial acetic acid and add 50ml di -sodium EDTA
and 20 ml ammonia ammonium chloride buffer solution. Warm on a
water bath, cool and add 50ml ethyl alcohol and 2ml dithizone. Titrate
the contents with 0.05M zinc sulphate until pink colour appears.

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