complete details for performing limit test for chlorides its is very helpful for the B.pharmacy 1 year students for both analysis as well as inoganic chemistry.

1. EXPERIMENT NO:1
LIMIT TEST FOR CHLORIDES
Prepared by
Dr Anumalagundam Srikanth
Dept. of Pharmaceutical Analysis

2. LIMIT TEST
Theory :
limit test are the quantitative and semi quantitative test designed to
identify and control small quantity of impurities which are likely to be present
in the drugs or pharmaceutical substance.
(or)
Limit test are used for identify and control small quantity of impurities in
drugs.

3. Aim:
To carry out the limit test for chlorides.
Apparatus :
Nessler’s cylinders 50 ml 2 nos., beakers, glass rod etc…,
Materials:
 Sodium bi carbonate (NaHCO3) (sample which does not contains chlorides)
Nitric acid (HNO3)
Hydrochloric acid (HCl)
Silver nitrate (AgNO3)

4. Solutions :
 silver nitrate solution ( 5% w/v) :
5 grams of silver nitrate dissolved in 100 ml distilled water.
 0.1 N HCl:
8.5 ml conc. HCl mixed with 1000 ml distilled water.
Preparation of 0.1 N HCl :
Assay of HCl normally available was 36 % ( 36 ml in 100 ml likely 360 ml in 1000 ml )
Density of HCl was 1.18
Density = mass/ volume
Mass= density X volume
Mass= 1.18 X 360 = 424.8 gm

5. No. of moles present in HCl
No.of moles present in sample = weight of sample / molecular weight
For HCl = 424.8 ( weight of HCl) / 36.5 (M.W)
= 11.63 N of HCl
We need to prepare 0.1 N by using the formula
N1 V1 = N2 V2
Where
N1 = 11.63 , V1 = ? , N2 = 0.1 , V2 =1000
11.63 X v1 = 0.1 X 1000
V1 = 0.1 X 1000/11.63
= 8.5

6.  Dil. Nitric acid (HNO3):
10.5 ml of concentrated nitric acid diluted with 89.5 ml of distilled water.
PRINCIPLE :
The limit test for chlorides is mainly used to control chloride impurities in inorganic
substances. If depends upon the precipitation of the chloride with silver nitrate in the
presence of dil. nitric acid and comparisons of the opalescence so obtained with a standard
opalescence contains a known quantity of chloride ions.
The reaction involved is as follows.

7. PROCEDURE:
Sample :
 Dissolve the specified quantity of the substance (NaHCO3 or any other material )
in 10 ml of distilled water and transfer to a Nessler cylinder or glass.
 Add 10 ml of dil.HNO3.
 Dilute to 50 ml with distilled water.
 Add 1 ml of AgNO3 solution.
 Stirr immediately with a glass rod, and set a side for 5 min the opalescence
produced is not greater than the standard opalescence.

8. Standard :
 Measure 1 ml of 0.1 N HCl and transfer to a Nessler cylinder.
 Add 10 ml of dil.HNO3.
Dilute to 50 ml with distilled water.
Add 1 ml of AgNO3 solution.
 Stirr immediately with a glass rod, and set a side for 5 min.

9. Observation :
Standard shows more opalescence than sample.
Report :
The given sample was passes limit test of chlorides.
References:
1. Practical pharmaceutical inorganic chemistry by Dr.G.Devala Rao., Birla
publications Pvt.Ltd., New Delhi. Page no: 36.
2. IP 1985