.
1. Description
White or pale
yellow powder or crystals.
2. Solubility
Freely soluble
in water forming an opalescent solution partly soluble in ethanol (95%).
3. Identification
A. Physical characteristics
Procedure
Take about 0.25
g of sample in a glass-stoppered test tube and add 25 ml of water. When shaken,
it produces plenty of foam.
B. Color reaction
Reagent required
0.1% w/v
solution of methylene blue
1M sulphuric
acid
Dichloromethane
Procedure
In clean
conical flask take 0.1 ml of solution prepared for identification A. Add 0.1 ml of a 0.1% w/v solution of
methylene blue, mix and add 2 ml of 1M sulphuric acid, add 2 ml of
dichloromethane and shake, the dichloromethane layer is intensely blue.
C. Reaction of sulphate
Reagent required
Barium chloride
solution
Ethanol AR
2M hydrochloric
acid
Procedure
In a clean,
test tube take about 10 mg of sample, mix with 10 ml of ethanol and heat to
boiling on a water bath. Shake frequently. Filter immediately and evaporate
ethanol. Dissolve the residue in 8 ml of water and 3 ml of 2M hydrochloric
acid; evaporate the solution to half of its volume and cool. Filter the
solution and to the filtrate add 1 ml of barium chloride solution. A white
crystalline precipitate is produced.
4. Reaction characteristics of sodium
Limit: A yellow crystalline precipitate is produced.
Reagent required
Magnesium
Uranyl Acetate solution
Dilute Acetic
acid
Procedure
Dissolve about
0.1 g of sample in 10 ml of water, acidify with dilute acetic acid and add a
large excess of magnesium Uranyl acetate solution. A yellow crystalline
precipitate is produced.
5. Alkalinity
Limit: Not more than 0.5 ml of 0.1M Hydrochloric acid is required to change the
color of the solution.
Reagent required
Phenol Red
solution
0.1M
hydrochloric acid
Procedure
In a clean and
dried conical flask, take 1g of sample, dissolve in 100 ml of CO2
free water and add 0.1 ml of phenol red solution. Not more than 0.5 ml of 0.1M
HCl is required to change the color of the solution.
5. Non esterified alcohol
Limit: Not more than 4%
Reagent required
Ethanol 95%
n-pentane AR
Anhydrous
sodium sulphate AR
Sodium Chloride
AR
Procedure
Weigh
accurately about 10 g of sample (W) and dissolve in 100 ml of water. Add 100 ml
of ethanol (95%) and extract the solution with three quantities, each of 50 ml
of n-pentane, adding sodium chloride, if necessary, to promote separation of
the two layers. Wash the combined organic layers with three quantities, each of
50 ml, of water. Dry the organic solution over anhydrous sodium sulphate,
filter and collect the organic layer on a silica dish, which was previously
dried at 110°C for two hours and weighed (W2). Evaporate the organic layer on a
water-bath until the odor of pentane is no longer detectable. Heat the residue
at 105°C for 15 minutes, cool in desiccators and weigh (W3).
Calculation:
W2 –
W3 x 100
% Non-esterified alcohol = ----------------------
W
Where,
W = Weight of
sample
W2 = Weight of
empty crucible
W3 = Weight of
crucible with residue
6. Sodium chloride and Sodium sulphate
Limit: Not more
than a total of 8.0%
Reagent required
2M nitric acid
Potassium
chromate solution
0.1M Silver
nitrate solution
0.05%w/v
Dithizone in acetone
1M nitric acid
Dichloro acetic
acid AR
Acetone AR
0.01M lead
nitrate VS
Procedure
Sodium chloride
Weigh
accurately about 5.0 g in a conical flask and dissolve in 50 ml of water, add
2M nitric acid dropwise until the solution is neutral to litmus paper, add 2
ml of potassium chromate solution and titrate with 0.1M silver nitrate. Each ml
of 0.1M silver nitrate is equivalent to 0.005844g of NaCl.
Calculation:
V x M
x F x 100
% Sodium
chloride = --------------------------
0.1 x W
Where,
V = Consumed
volume of 0.1 Silver nitrate
M = Molarity of
0.1 M Silver nitrate
F = Factor
W= Weight of
substance
Sodium Sulphate
Procedure
Weigh
accurately about 0.5 g in a conical flask and dissolve in 20 ml of water, warm
gently if necessary, and add 1 ml of a 0.05% w/v solution of Dithizone in
acetone. If the solution is red, add 1M
nitric acid dropwise, until it becomes bluish green. Add 2 ml of dichloroacetic
acid solution and 80 ml of acetone and titrate with 0.01M lead nitrate until a
permanent orange-red color is obtained. Each ml of 0.01M lead nitrate is
equivalent to 0.001420g of Na2SO4.
Calculation:
V x
M x F x 100
% Sodium
sulphate = --------------------------
0.1 x W
Where,
V = Consumed
volume of 0.1 Lead nitrate
M = Molarity of
0.1 M Lead nitrate
F = Factor
W= Weight of
substance
7. Assay
Limit: Not less than 85.0% sodium alkyl sulphate
Reagent required
Chloroform AR
Dilute
sulphuric acid
Dimethyl
yellow-oracet blue B solution
0.004M
Benzothonium chloride VS
Procedure
Weigh
accurately about 1.15g dissolve in sufficient water to produce 1000 ml, warm if
necessary. Transfer 20.0 ml to a
separator, add 15 ml of chloroform, 10 ml of dilute sulphuric acid and 1 ml of
dimethyl yellow-oracet blue B solution and titrate with 0.004M Benzothonium
chloride, shaking vigorously and allowing the layers to separate after each
addition, until the chloroform layer acquires a permanent clear green
colour. Each ml of 0.004M Benzothonium
chloride is equivalent to 0.001154g of sodium alkyl Sulphate, calculated as C12H25NaO4S.
Calculation:
V x M x F x
100
% Sodium
chloride = -----------------------
0.1 x
W
Where,
V = Consumed
volume of 0.1 Lead nitrate
M = Molarity of
0.1 M Lead nitrate
F = Factor
W= Weight of
substance
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