LABOROTORY MANUAL OF PHYSICAL PHARMACEUTICS · The determination of equivalence point of a titration by means of conductance ... Shake the solution to make it homogeneous. This is

© Department of Pharmaceutics, H. R. P. I. E. R, Shirpur, 2016-17 1 | P a g e

LABOROTORY

MANUAL

OF

PHYSICAL

PHARMACEUTICS


LABORATORY INSTRUCTIONS

1. Laboratory should be cleaned two times in a day, first in the morning and second

in evening before closing the laboratory.


This laboratory manual is prepared for only Students of H .R. P. I. P. E.R.

Shirpur. It should never be used by anyone without permission. The main objective

of this manual is to enhance student-teacher interaction during performing

experiments. Wide margin on every page of this manual can be used by students for

noting important points.

It is hoped that the present Laboratory practical Book in its revised and

2. Student should enter in the laboratory five minutes before the practical timing.

3. Maintaining cleanliness is the job responsibility for every student in the

laboratory.

4. Silence should be maintained in the laboratory and any disturbance should be

strictly avoided.

5. Going out and coming in between practicals should be avoided strictly.

6. Chatting unnecessary in the corridors should be avoided. Enter the lab with

clean and neat apron.

7. Keep the working table clean and neat

8. Maintain discipline in the laboratory.

9. Complete you practical record in the laboratory.

10. Be careful while using chemicals in the laboratory.

11. Turn off the burners of the gas when it is not required.

12. Close the water taps properly after use.

13. If you have any allergic problem you must use hand glows while handling the

chemicals.

14. For any problem, consult concerned teacher or technician of the laboratory.

15. Wearing ornaments while doing the experiment is strictly avoided.

PREFACE


INDEX

Signature of Lab Instructor

No. Title of Experiment Page

No. Remarks Sign

1. Introduction to laboratory Instrument and Glass ware.

2. To determine the normality of given strong acid by

conductometric titration with strong base

3. To determine dissociation constant of given acid by

conductometry

4. To determine percent composition of given binary mixture

by using viscosity measurement

5. To determine relative viscosity of the given liquid using

Ostwald’s viscometer

6. To determine surface tension of given liquid samples using

stalagnometer

7. To determine average particle size of given powder sample by

optical microscopy

8. To determine average particle size of given powder sample by

sieving method

9. To Determine Critical Micelle Concentration (CMC) of the

Sodium Laurel Sulphate by surface tension measurement

10. To determine various derived properties of given powder

sample

11. To Determine Hydrophile-Lipophile-Balance (HLB) of

Glyceryl Mono Stearate

12. To study calibration and weights

13. To study calibration and weights

14. Calibration of volumetric apparatus like, Pipette burette etc

15. Preparation and standardization Bases (NaOH).

16. Preparation and standardization of acids (HCl).



Aim- Introduction to laboratory Instrument and Glass ware.

Theory-

1. Glass wares

2. Beakers

3. Funnel

4. Porcelain apparatus

5. Pipettes

6. Burettes

7. Analytical Balance

8. Weights

Result – All necessary laboratory instruments were handled and studies

Experiment No.: 1 Date:

Laboratory Instrument and Glass Ware


Aim:

To determine the normality of given strong acid by conductometric titration

with strong base.

Learning objective:

You will be able to explain-

1. Conductometric titration

2. Equivalence point

3. Conductance of solution and its unit

Introduction:

The electrolytic conductors obey Ohm’s law. It states that strength of the current

(I) passing through the conductor of resistance (R) is directly proportional to the

potential difference (V) applied across the conductor.

The resistance (R) is directly proportional to the length (l) and inversely

proportional to cross section (a) of the conductor.

Where, = specific resistance

When l = 1cm, a = 1 cm2 and R = .

The unit of specific conductance is mho.cm-1

The Conductance of a solution of electrolyte is determined by conductivity cell.

V

R

I =

l

a

R l

a

R =

1

Specific conductance = = KC


Conductometric Titration


Fig: Conductometric titration

Principle:

The determination of equivalence point of a titration by means of conductance

measurement is known as conductometric titration.

Conductance depends on the number of ions and mobilities of the ions. During

titration, number of ions with different mobilities are changing, so conductance changes

and hence equivalence point can be determined.

At equivalence point equal amount of acid and base reacts.

Requirements:

Apparatus

1. Conductivity bridge,

2. Conductivity cell,

3. Burette,

4. Pipette,

5. Beaker (100cm3)

Chemicals:

1. Strong acid (Given),

2. NaOH (0.5N exact)

3. Conductivity water

Procedure – I:

For the determination of conductance using conductivity meter proceed as follows –

1. Switch on the instrument and wait for 10 minutes

2. Select mho range.

3. Dip the cell in the solution and connect it to the conductometer.


4. Select the appropriate range and read the reading on screen. In digital

conductometer directly conductance is shown on the screen.

Procedure – II:

1. Now wash the conductivity cell and beaker with conductivity water.

2. Pipette out 10cm3 of given acid solution in a beaker. Place it on magnetic stirrer.

Put stirrer in it. Dip the conductivity cell in it. Add sufficient amount of

conductivity water to cover the electrodes completely. Connect the cell to

conductometer. Stir the solution.

3. Measure conductance of solution.

4. Fill the burette with 0.5N NaOH solution.

5. Add 0.2cm3 NaOH solution in a beaker containing strong acid solution. Stir the

solution.

6. Measure conductance.

7. Repeat procedure (5) and (6) until equivalence point is obtained.

Observation table:

Sr.

No.

Volume of NaOH

(in cm3)

Conductance (1/R)

(in mho)

1. 0.0

2. 0.2

3. 0.4

4. 0.6

5. 0.8

6. 1.0

7. 1.2

8. 1.4

9. 1.6

10. 1.8

11. 2.0

12. 2.2

13. 2.4

14. 2.6

15. 2.8

16. 3.0

17. 3.2

18. 3.4


19. 3.6

20. 3.8

21. 4.0

Plot a graph of conductance Vs cm3 of NaOH added.

Find the equivalence point Z from the graph.

Calculations:

N1V1 = N2V2

Where,

N1 = Normality of acid solution

V1 = Volume of acid = 10cm3

N2 = Normality of base solution

V2 = Volume of base = Z cm3

Result:

Equivalence point = ______________ cm3.

Normality of acid = _______________ cm3.

N2V2

V1

N1 = 0.5 x Z

10

=


Answer the following

1. Define equivalence point.

2. What is conductometric titration?

3. Write a reaction between HCl and NaOH.

4. Write advantages of conductometric titration.

5. What is conductivity cell? Explain with figure.


Aim:

To determine dissociation constant of weak monobasic acid by conductometric

measurement.

Aim:

To determine dissociation constant of given acid by conductometry.

Learning objective:

You will be able to explain –

1. Cell constant

2. Equivalence conductance and its units.

3. Equivalence conductance at infinite dilution.

4. Kohlrausch’s law

5. Degree of dissociation and dissociation constant

Introduction:

Consider 1 mole of weak acid HA present in V litre. Let be the degree of

dissociation. The dissociation is represented by equation –

HA H+ + A

Initial moles 1 0 0

Moles at equilibrium (1- )

Active masses (1- )/V /V /V

Dissociation constant = Ka =


Conductometric Measurement

[H+][A]

[HA]

(/v) x (/v)

(1-/v)

=

2

(1-) x V

=

2C

1-

=


Where, C is concentration in moles/lit of acid solution. The degree of dissociation ()

can be determined by conductivity measurement.

c represents equivalent conductance at concentration C.

o represents equivalent conductance at zero concentration.

Then,

Substituting the value of and C, the dissociation constant can be determined.

o is obtained by the use of Kohlrausch’s law.

o = o+ + o

Fig: Conductometric measurement

Principle:

Equivalent conductance c is conductivity of solution containing one equivalent

of the solute, when placed between two sufficiently large parallel electrodes which are

1cm apart.

c = Kc x V

Where V = is the volume in cc containing one gram equivalent solute. The unit

is mho cm2.

Equivalent conductance increases with increase in dilution. At infinite dilution

when dissociation is complete the value of equivalent conductance is maximum called

equivalent conductance at infinite dilution or zero concentration represented by o.

c

o

=


Apparatus

1. Conductivity bridge,

2. Conductivity cell,

3. Pipette

4. Beaker

Chemicals

1. 0.02M KCl,

2. 0.1N monobasic acid,

3. Conductivity water

Procedure:

Part A: Determination of cell constant.

1. Wash the cell with conductivity water. Rinse the cell and beaker with 0.02M

KCl solution. Take sufficient quantity of 0.02M KCl solution so that electrodes

are completely covered with the solution about 50cm3.

2. Connect the cell to Conductivity Bridge.

3. Measure the conductance.

Observation table:

Room temperature = ____________ oC.

Solution Conductance (mho)

0.02M KCl

Calculations:

=

Part B: Determination of dissociation constant.

Specific conductance of 0.02M KCl

Conductance of 0.02M KCl solution observed Cell constant = =


1. Wash the cell and beaker with conductivity water. Dry it. Pipette out 50cm3 of

0.1N acetic acid given acid in a beaker (use 25cm3 pipette). Dip the cell in the

solution and measure the conductance.

2. Withdraw 25cm3 of 0.1N acetic acid from beaker. Add to it 25cm3 conductivity

water. Shake the solution to make it homogeneous. This is 0.05N acetic acid.

Measure conductance.

3. Withdraw 25cm3 0.05N acetic acid from the beaker. Add to it 25cm3

conductivity water. Shake the solution. This is 0.025N acetic acid. Measure

conductance.

4. Withdraw 25cm3 of 0.05N acetic acid from the beaker. Add to it 25cm3

conductivity water. Shake the solution. This is 0.0125N acetic acid. Measure the

conductance.

Observation table:

Concentrati

on of acid

Conductance

(mho)

Specific

conduct

ance

Kc (mho/cm)

Equivalent

conductan

ce c

(mho/cm)

Degree of

dissociati

on

Dissociati

on

constant

(Ka)

0.1N

0.05N

0.025N

0.0125N

Calculations:

1. Specific conductance = Kc = Cell constant () x Conductance


2. Equivalent conductance = c =

3. Degree of dissociation = =

Specific conductance (Kc) x 1000

Concentration(C)

Equivalent conductance (c)

Equivalent conductance at zero concentration ()


4. Dissociation constant = Ka =

Find the mean value of Ka.

Result:

Dissociation constant of given acid is _______________.

2C

(1-)


Answer the following.

1. What is specific conductance? Give its unit.

2. What is cell constant? Give its unit.

3. What is equivalent conductance? Give is unit.

4. What is equivalent conductance at infinite dilution?

5. Define and explain Kohlrausch’s law.


Aim:

To determine percent composition of given binary mixture by using viscosity

measurement.

Learning objective:

You will be able to explain:

1. Viscosity

2. Coefficient of viscosity

3. Specific gravity

Theory:

Viscosity of the liquid is the characteristic of the liquid and for a given liquid it change

with temperature. The viscosity decrease remarkably as the temperature of the the

liquid is raised. Poiseuillie’s equation is use, for the direct measurement of viscosity. It

requires the measurement of rate of flow of liquid under definite pressure through the

capillary of same radius.

The reciprocal of coefficient of viscosity (η) is called as fluidity (Ф)

Consider mixture of two liquids. When the two liquid are similar and they do not form

complex in the mixture then their fluidity is additive .The fluidity of the mixture can be

calculated by, Ф= X1 ; X2 Д2 where Ф is fluidity of mixture , Ф1 -fluidity of liquid

1, Ф2 – fluidity of liquid 2, x1 and x2 are mole fraction of liquid 1 and 2 respectively.

The composition of mixture can be studied by viscosity technique.


% Composition of Binary Mixture

1 = ------ η



Apparatus : Ostwald viscometer, stopwatch, specific gravity bottle, dryer.

Chemicals : Liquid A ( Ethanol), Liquid B ( Distilled water). Acetone, mixture of A

and B of various composition will be provided.

Procedure :

Part A : Preparation of Solution.

If the mixture of liquid A and B are not provided they can be prepared as per

following table.

Liquid % Composition

A B

C 80 20

D 60 40

E 40 60

F 20 80

G Unknown Unknown


Part B : Determination of flow time for the liquids.

1. Clean the viscometer with distilled water and rinse with acetone. Dry it by drier.

2. Take fix volume (10 ml or 20 ml) of liquid A in the brode limb by using pipette.

3. Suck the liquid using rubber tube till it reaches slightly above mark X.

4. Allow the liquid using to flow downward side and start the stop watch when the

liquid level coincide with mark X.

5. Note down the time require to flow the liquid from mark X to mark Y. Repeat

for two to three times and find out mean time.

6. Repeat the same procedure for same volume of liquid B, C, D, E and unknown

liquid G. ( Generally 50 % A + 50 % B is taken as unknown).

7. The densities of pure liquid A,B and mixture should be provided. If it is not

provided they can be determine by using specific gravity bottle as part A in

experiment no. 1.

Observation Table :

No. Liquid % Composition Flow time t in sec. Density

(d) g cm3

D x t poise

A B 1 2 3 Mean

1

2

3

4

5

6

7

A

B

C

D

E

F

G

100

0

80

60

40

20

0

100

20

40

60

80

Unknown

Graph and Calculations:

Plot a graph of % composition with respective A and B against dxt, separetly.

From (d x t ) values for the mixture with unknown composition we can

determine composition of mixture. The nature of graph is as shown in figure.


Fig. 2 : d x t verses recent A plot or B plot.

Result :

Liquid % A % B

Unknown

Oral Questions :

1. Define fluidity

0 20 40 60 80 100 % % A

(dxt

)


2. What is unit of density of liquid ?

3. Why acetone is use in viscosity experiment?

4. How density of liquid is determine ?

5. Explain the nature of graph dt Vs percent A.


Aim:

To determine relative viscosity of the given liquid using Ostwald’s viscometer.

Learning objective:

You will be able to explain:

1. Viscosity

2. Coefficient of viscosity

3. Specific gravity

Introduction:

Viscosity is a property of liquid due to which it resist the relative motion of

successive layers of liquid. Viscosity is a force of friction between layers of liquid.

Viscosity is measured in terms of viscosity coefficient ‘’. The unit is poise.

Viscosity coefficient of a liquid is given by Poiseuille’s equation –

Where, P = pressure due to column of liquid,

r = radius of capillary of length l and volume V,

t = time taken by liquid to flow through capillary.

For this method experiments deals with determination of time of flow of fixed volume

‘V’ of liquid through uniform capillary of length ‘l’ and radius ‘r’ may be done by

using Ostwald’s viscometer.


Relative Viscosity of Liquid

P r4 t

8 V l =


Principle:

Flow is a characteristic property of liquids. Hence, the liquids are also called as

fluids. The rate of flow depends on the nature of the liquid and the extent of

intermolecular force of attraction between the molecules of liquid. The motion of a

liquid in a glass tube may considered to be composed of number of molecular layers

arranged one over other. The layers in contact with the tube s almost stationary. The

second layer moves slowly, the third little fast and so on. Each layer exerts a drag on

the other. This internal friction between layers of liquid is called as viscosity of liquid.


Requirements:

Apparatus:

1. Ostwald’s viscometer,

2. Pipette,

3. Stand,

4. Stop watch

Chemicals:

1. Pure liquid A

2. Pure liquid B


Procedure:

1. Clean the viscometer with little acetone and dry it by blowing hot dry air "through

it. (Hold broader limb of viscometer to avoid breakage). Then mount on cotton and

clamp it to stand in perfectly vertical position.

2. Fix carefully rubber tube to the narrower tube (For easy fixing apply little grease to

the outer side of glass tube).

3. Take fixed volume (10 or 20 cm3, depending on size of viscometer) of liquid A in

the broader limb with the help of a pipette.

4. Suck the liquid using rubber tube till it reaches slightly above the mark X (Avoid

sucking liquid in rubber tube. Organic liquids may dissolve rubber which chokes

the capillary, introducing errors in the observations. Also sometimes the vapors may

be dangerous to health and hence avoid inhaling).

5. Allow the liquid to flow freely. Start the stop watch when it touches the upper mark

X and stop it when it, reaches the lower mark Y. Hence, determine the time of flow.

Take three trials. Restore that liquid in its container.

6. Wash the viscometer with acetone. Dry the viscometer by passing hot air through it

with help of dryer. Put 10 or 20 cm3 of water in broader limb. Suck the liquid above

mark X and allowed to flow the liquid. Find the time of flow for water.

7. Determine density of liquid A by using specific gravity bottle as follows:

(a) Clean specific gravity bottle with acetone, dry it and weigh it empty.

(b) Fill it with liquid A, stopper it and dry it from outside and weigh it. Then

restore the liquid in its container.

(c) Finally, fill the specific gravity bottle with water, stopper it, dry it from

outside and weigh it. Tabulate your observations as follows.


Observation table 1:

Liquid Time of flow Density/g

cm-3

d x t

1 2 3 Mean

t/sec

Liquid A

Liquid B

Water


1. Weight of empty specific gravity bottle = W1g _______g

2. Weight of specific gravity bottle with

liquid A

= W2g _______g


liquid B

=W3g _______g


water

= W4g _______g

5. Weight of liquid A = (W2-W1) g _______g

6. Weight of liquid B =(W3 – W1)g _______g

7. Weight of water =(W4 – W1) g

_______g


Density of water ____g cm-3 at ____oC (given)

Calculations:

I. Density of liquid A & B

Density of liquid A = =

Density of liquid B = Weight of B = W2 – W1

W4 – W1

Weight of A

Weight of water

W2 – W1

W4 – W1

Weight of water


II. Calculate the relative viscosity of liquid using following formula.

=

Results:

Liquid A B

Density g/ cm-3

Viscosity of Liquid in poise

Question for oral examination

1. Define the terms viscosity

2. Define viscosity coefficient. Give its unit.

3. What is specific gravity?

4. Which instrument is used for measurement time of flow?

5. What is mean by relative viscosity

A dA x tA

dB x tW x B = poise


Aim:

To determine surface tension of given liquid samples using stalagnometer

Learning objective:

You will be able to explain

1. Surface

2. Interface

3. Surface tension

Introduction:

The molecules at the surface of a liquid are subjected to an unbalanced force of

molecular attraction as the molecules of the liquid tend to pull those at the surface

inward while the vapor does not have as strong an attraction. This unbalance causes

liquids to tend to maintain the smallest surface possible. The magnitude of this force is

called the surface tension. When this lowest possible energetic state is achieved the

surface tension acts to hold the surface together where the force is parallel to the

surface. The symbol for surface tension is "gamma". Conventionally the tension

between the liquid and the atmosphere is called surface tension while the tension

between one liquid and another is called interfacial tension.

Principle:

The principle involved in falling drop method is described as follows. It is very

convenient and quick method.

In this technique, stalagnometer is used to measure surface tension; it measures

the strength of cohesive forces of liquids. For example, water has strong cohesive

forces, so surface tension is more, on the other hand liquid such as benzene exhibits low

surface tension compared to water.

The lower the surface tension of liquid, the smaller the size of drops formed.

Then more amount of drops are formed for same volume of a liquid.


Surface tension


Hence by simply counting the number of drops for an unknown liquid and water, is

sufficient to calculate surface tension. The above arguments are valid when the

densities of liquids are same.

Requirements:

Apparatus:

1. Stalagnometer,

2. Specific gravity bottle,

3. Stop watch

4. Stirrer,

5. Beaker,

Chemicals

1. Acetone,

2. Benzene

3. Toluene

Procedure:

1. Select a clean stalagnometer, deep it in a beaker of water and suck the water

through rubber tube which is attached, up to a level higher than upper mark P.

2. Leave the rubber tube, and allow water to flow down.

3. Start counting water drops when water meniscus just passes the mark P until it

crosses the lower mark Q.

4. Deep the apparatus in beaker of next liquid and follow same procedure to count

number of drops formed of each liquid.

Formula:

ϒ1 = n1ρ2 = No of drops of water X Density of unknown

ϒ2 n2 ρ1 No of drops of unknown X Density of water


Observation table:

Sr. No. Liquid No. of drops

counted

Density

gm/cm3

1. Water

2. Acetone

3. Benzene

4. Toluene

Calculations:

A) Determination of Densities

1. Acetone –

Wt of gravity bottle = ----- gms

Wt of acetone = ------ gms

Density = Wt of acetone / Wt of gravity bottle

Density = ---------- gms/cm3

2. Benzene –


Wt of benzene = ------ gms

Density = Wt of benzene / Wt of gravity bottle


3. Toluene –


Wt of toluene = ------ gms

Density = Wt of toluene / Wt of gravity bottle


B) Determination of Surface tension

1. Acetone –


2. Benzene –

3. Toluene –

Result:

The Surface tension of given liquid samples using drop count method was found

as

Sr. No. Liquid Surface tension

dy/cm

Density

gm/cm3

1. Water

2. Acetone

3. Benzene

4. Toluene


Answer the following

1. Define surface tension.

2. Define surface free energy.

3. Enlist various methods used to determine surface tension.


Aim: To determine average particle size of given powder sample by optical microscopy

Learning objective:


1. Micromeritics

2. Fundamental & Derived properties of powders

3. Methods to determine particle size

Introduction –

Of the various methods employed for particle size determination, the optical

microscope method is the only one in which direct observation is made of the size of

the particles. Even this method has one drawback in that it has a tendency to measure

the largest dimensions unless the particles are properly dispersed with random

orientation. Also, the method is too much time consuming for extensive use between

purchaser and supplier for determining conformity to specifications. But it may be used

advantageously for two purposes, namely, (a) as a basis of calibration for faster

methods such as those involving sedimentation and (b) in the determination of the

particle size of routine samples, especially in the cases where particles are of such

shape that they do not obey Stokes’s law.

Outline of method:

A representative sample of the powder to be sized is dispersed and placed on a

glass slide. The particles are viewed through a microscope by means of transmitted

light. The areas of the magnified images of the particles are compared with those of the

reference circles of known size inscribed on a graticule and simultaneously visible.

The relative numbers of particles in each of a series of size classes are determined.

These numbers, expressed as percentages, constitute the size distribution by number.

From the relative number in the size classes the relative volumes are calculated,


Optical microscopy


assuming that particles of all sizes have the same shape. The relative volumes,

expressed as percentages, constitute the size distri-bution by volume. The same is the

size distribution by weight also if particles of all sizes have the same density.

Fig : Optical Microscope

Fig : Eye piece micrometer


Fig : Calibration of eye piece micrometer by stage micrometer

Procedure:

1. The eyepiece micrometer is calibrated if not already calibrated.

2. A dilute suspension of representative sample is prepared and little of it is

mounted on glass slide. The mounted material is placed on mechanical stage

to observe through a microscope.

3. The particle diameter in both directions is measured and recorded for at least

600 particles

4. The data is represented as a size frequency distribution curve and average

particle size is calculated.

Observation Table:

Calculations:

1) Calibration of eyepiece micrometer

No. of lines of eyepiece micrometer = No. of lines of stage micrometer

---- Lines of eyepiece micrometer = 10 lines of stage micrometer

1 line of eyepiece micrometer = X lines of stage micrometer

Particle No No. of lines

covered

Particles

size

Particle No No. of lines

covered

Particles size

1 8

2 9

3 10

4 11

5 -

6 -

7 600

Total ( N)


X = 1X10

------

Calibration factor (X) = -------------------μm

Therefore, 1 line of eyepiece micrometer = ------μm

2) Average particle size

Average particle size = Σ of particle size of all particles

Total no of particles counted

Therefore, Average particle size = N

600

Avarage particle size = ------ μm

Result:

The average particle size of given powder sample was found to be ----μm

Answer following question:

1. Define Micromeritics, write its pharmaceutical applications


2. What are fundamental properties of powder?

3. Enlist various methods to determine particle size

4. What would be the size range that can be determined using optical microscopy?


Aim: To determine average particle size of given powder sample by sieving method

Learning objective:


1. Micromeritics

2. Fundamental & Derived properties of powders

3. Methods to determine particle size

Introduction:

There are different methods for determining the particle distribution. The choice of a

particular method depends primarily on the dispersion status, i.e. on the degree of fineness of

the sample.

The oldest and best-known method is particle size determination by sieve analysis. The

particle size distribution is defined via the mass or volume. Sieve analysis is used to divide the

particulate material into size fractions and then to determine the weight of these fractions. In

this way a relatively broad particle size spectrum can be analyzed quickly and reliably.

During sieving the sample is subjected to horizontal or vertical movement in

accordance with the chosen method. This causes a relative movement between the particles and

the sieve; depending on their size the individual particles either pass through the sieve mesh or

are retained on the sieve surface. The likelihood of a particle passing through the sieve mesh is

determined by the ratio of the particle size to the sieve openings, the orientation of the particle

and the number of encounters between the particle and the mesh openings. As explained later,

the likelihood of passage and therefore the associated quality of the sieved sample also depends

on the sieve movement parameters and the sieving time.

Despite new developments in the field of optical particle measuring instruments it

remains a proven, reliable and inexpensive method for determining the particle size. However,

the result of a sieve analysis is only meaningful and reproducible when the preconditions

described above are fulfilled. Modern sieve shakers with digital settings, such as the AS-

control series from Retsch, supported by a powerful evaluation software, permit exact sieving

results that are reproducible throughout the whole world.


Sieving method


Fig: Mechanical sieve Shaker with nest of sieves.

Apparatus: - Sieve shaker, sieves of different numbers, Beaker etc.

Procedure:

1. About five sieves are arranged keeping one above other in a series with the

coarsest at the top and the finest at bottom

2. Around 100 gms of pre-weighed sample is placed on the top sieve.

3. The nest of sieve is shaken for about 20 minutes preferably in sieve shaker.

4. The quantity of sample retained on each sieve is weighed.

5. The average particle size is determined as weight fraction and the

distribution is expressed in a cumulative over size curve

Observation Table:

Sr.

No

Sieve No

(Passed/

retained)

Arithmetic

mean of

opening (mm)

Wt.

retained (g)

on smaller

sieve

% Retained % Retained X

Ar. mean of

opening (mm)


1 10 1.7

2 22 0.710

3 44 0.355

4 60 0.250

5 85 0.180

6 120 0.125

7 PAN -

Σ

Sr.

No

Sieve No

(Passed/

retained)

Arithmetic

mean of

opening (mm)

% Wt.

retained (g)

Cumulative

% over size

Cumulative %

under size

1 10 1.7

2 22 0.710

3 44 0.355

4 60 0.250

5 85 0.180

6 120 0.125

Calculations:

The Average diameter = Σ (% wt. retained X Ar. Mean opening)

100


Therefore, the average diameter = ----------- mm

Graph:

The particle size- weight distribution can be expressed either as cumulative over size or

cumulative under size

Fig. 2: Particle size Vs . Cumulative over size / under size curve

Result:

The average particle size of given powder sample was found to be ----μm

Answer following question:

1. Define Micromeritics, write its pharmaceutical applications

0 0.4 0.8 1.2 1.6 1.8 Particle size

Cu

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ize


2. What are fundamental properties of powder?

3. Enlist various methods to determine particle size

4. What would be the size range that can be determined using sieving method?


Aim: To Determine Critical Micelle Concentration (CMC) of the Sodium Laurel

Sulphate by surface tension measurement,

Learning objective:


1. Surface acting agent

2. Surface tension

3. Critical micelle concentration

Introduction:

Surfactants, sometimes called surface-active agents or detergents, are among the

most versatile chemicals available. They have applications in many areas, including

chemistry (chemical kinetics or equilibria), biology (as membrane mimetics), and

pharmacy. Surfactants are amphiphilic materials containing both nonpolar long-chain

hydrocarbon “tail” and polar, usually ionic, “head” groups. In polar solvents, for

example water, this dual character of the amphiphile leads to self-association or

micellization: the surfactant molecules arrange themselves into organized molecular

assemblies known as micelles. The hydrophobic part of the aggregate forms the core of

the micelle, while the polar head groups are located at the micelle–water interface in

contact with and hydrated by a number of water molecules. Depending on the chemical

structure of the surfactant, its micelle can be cationic, anionic, ampholitic

(zwitterionic), or nonionic. This unique property

of surfactants makes aqueous surfactant solutions micro heterogeneous media; that is,

they are heterogeneous on a microscopic scale, even though they are often

homogeneous macroscopically.

Definition of CMC

It is the concentration (actually an arbitrary concentration within a narrow

range) of surfactant, above which micelles formation starts, is called the critical micelle


Critical Micelle Concentration

Preparation of p-Nitro acetanilide from Acetanilide


concentration (CMC). Above the CMC, monomers and micelles exist in dynamic

equilibrium.

Micelles are small colloidal particles, relative to the wavelength of light. When

micelles form, the aqueous surfactant solution behaves as a micro heterogeneous

medium. The value of the CMC can be determined by the change in the

physicochemical properties of the surfactant solution as the surfactant concentration

increases.

Experimentally, the CMC is found by plotting a graph of a suitable physical

property as a function of surfactant concentration. An abrupt change of slope marks the

CMC. The choice of CMC is never unambiguous, since the change in slope occurs over

a more or less narrow range of concentrations, whose magnitude depends on the

physical property being measured and sometimes on the nature of the data and on the

way they are plotted.

The CMC can be affected by many variables (6), temperature and pressure

being of relatively minor importance. It decreases with increasing hydrocarbon chain-

length of the apolar groups, and for ionic surfactants it also depends on the nature and

concentration of counter ions in solution. Added electrolytes decrease the CMC, and

the effect increases with decreasing charge density of the counterion

Fig: Diagrammatic representation of critical micelle concentration

Apparatus: - Stalagnometer, pycnometer, Beaker etc.


Procedure:

1. A stock solution of 5% sodium lauryl sulphate (SLS) is prepared by

dissolving 5 grams of SLS in 100 ml water in volumetric flask.

2. A series of concentration of SLS is prepared by diluting stock solution as

follows

A. 50 mg per 100 ml ( 1 ml to 100 ml)

B. 100 mg per 100 ml ( 2 ml to 100 ml)

C. 150 mg per 100 ml ( 3 ml to 100 ml)

D. 200 mg per 100 ml ( 4 ml to 100 ml)

E. 250 mg per 100 ml ( 5 ml to 100 ml)

F. 300 mg per 100 ml ( 6 ml to 100 ml)

G. 400 mg per 100 ml ( 8 ml to 100 ml)

H. 500 mg per 100 ml ( 10 ml to 100 ml)

3. Surface tension of prepared solutions is determined by drop count method

using stalagnometer.

4. A graph of surface tension on Y axis Vs Concentration of SLS on X axis is

plotted to determine CMC.

Observation Table:

Sample Conc. in mg/

100 ml

No. of drops

(mean of 3

observations)

Density

gms/cm3

Surface

tension

dynes/cm

Water -

A 50

B 100

C 150

D 200

E 250

F 300

G 400

H 500

Calculations:

I. Determination of Densities


Densities of all solutions (sample A to H and water) are determined

using specific gravity bottle as discussed previously.

II. Determination of Surface tension

To determine specific gravity, drop count method is followed using

stalagnometer as discussed previously (Experiment no 5, P.No- 27 -31)

Graph:

A graph of surface tension on Y axis Vs Concentration of SLS on X axis

is plotted to determine CMC.

Fig. 2: surface tension Vs. Concentration of SLS

Result:

The Critical Micelle Concentration (CMC) of Sodium lauryl sulphate is found to be ----

--- mg/100ml

0 50 100 150 200 250 Conc.

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Aim: -

To determine various derived properties of given powder sample

Learning objective:


1. Micromeritics and its pharmaceutical applications

2. Bulk density, tapped density

3. Carr’s index and angle of repose

Introduction: -

Densities of particles: Density is defined as weight per unit volume (W/V).

Types of densities:

A- True density

The true density, or absolute density, of a sample excludes the volume of the

pores and voids within the sample.

Fig: Apparatus for determination of Bulk density

B- Bulk density (w/v) the bulk density value includes the volume of all of the

pores within the sample.


Derived Properties of Powder


The bulk density of a powder is the ratio of the mass of an untapped

powder sample and its volume including the contribution of the interparticulate

void volume.

The bulk density of a powder is determined by measuring the volume of

a known weight of powder sample that may have been passed through a seive,

into a graduated cylinder, or by measuring the mass of a known volume of

powder that has been passed through a volumeter into a cup or a measuring

vessel.

Bulk density = weight / bulk volume

C -Tapped density

It is defined as mass divided by the tapped volume. The tapped density

is an increased bulk density attained after mechanically tapping a container

containing the powder sample. Tapped density is obtained by mechanically

tapping a graduated measuring cylinder or vessel containing a powder sample.

The mechanical tapping is achieved by raising the cylinder or vessel and

allowing it to drop under its own weight a specified distance by either of three

methods as described below. Devices that rotate the cylinder or vessel during

tapping may be preferred to minimize any possible separation of the mass

during tapping down.

Tapped density = weight / true volume

D- Carr’s compressibility index

A volume of powder is filled into a graduated glass cylinder and

repeatedly tapped for a known duration. The volume of powder after tapping is

measured.

Tapped density – Poured or bulk density

Carr’s index (%) = x 100

Tapped density

E – Angle of Repose (θ)


The frictional forces in a loose powder can be measured by the angle of

repose θ.

θ = the maximum angle possible between the surface of a pile of powder

and horizontal plane = coefficient of friction μ between the particles:

tan θ = μ

tan θ = h / r

r = d / 2

θ = tan -1(h / r)

The rougher and more irregular the surface of the particles, the higher

will be the angle of repose

Chemicals: - Powder samples such as starch, microcrystalline cellulose etc

Apparatus: - Funnel, graduated measuring cylinder, burette stand, bulk density

apparatus etc.

Procedure: -

Part A – Determination of Bulk density and Tap density

i) Weigh accurately 20 gm of sample powder.

ii) Transfer it carefully in a graduated measuring cylinder and note down volume

as V1 ml.

iii) Place the cylinder containing sample in bulk density apparatus. Adjust apparatus

for 100 tapings and operate it. Record the volume occupied by powder as V2

ml

Part B: - Determination of Angle of repose

i) Take a clean and dry funnel with a round stem of 20 to 30 mm diameter with

flat tip and attach it to the burette stand

ii) Place a graph paper sheet below the funnel on clean and dry platform

iii) Adjust the distance between lower tip of funnel and sheet to some specified

height.

iv) Gently pour powder sample in funnel from top till a heap of powder forms and

touches to the lower tip of funnel.

v) Using a pencil, draw a circle around the heap covering approximately 90 % of

total powder

vi) Repeat the procedure four times to obtain average reading

vii) Find the average diameter and radius of the each drawn circle

Horizontal surface

Heap of powder

h

D

f


Calculations: -

1) Bulk Density:

Weight of powder (W1) = ------------ gms

Bulk volume of powder (V1) = --------------- ml

Bulk Density = W1

V1

Bulk Density = ------------ gm/ml

2) Tapped Density:

Weight of powder (W1) = ------------ gms

Tapped volume of powder (V2) = --------------- ml

Tapped Density = W1

V2

Tapped Density = ------------ gm/ml

3) Carr’s index:

Tapped density – Poured or bulk density

Carr’s index (%) = x 100

Tapped density

Carr’s index (%) = ------------ %

4) Angle of repose

Angle of repose (θ) = tan -1(h / r)

Angle of repose (θ) = --------- 0

Result:-

The derived properties of given powder sample are measured and reported as

below


Sr. No. Derived properties Result

1 Bulk Density

2 Tapped Density

3 Carr’s index

4 Angle of repose

Answer the following question:

1. Write a short note on powder characterization

2. Define porosity, explain its importance


Preparation and Standardization of Solution

Aim: -

To Determine Hydrophile-Lipophile-Balance (HLB) of Glyceryl Mono Stearate

Learning objective:


1. Surface active agents

2. Hydrophilic lipophilic balance and its significance

3. Methods to determine HLB

Introduction: -

The Hydrophile-Lipophile-Balance (HLB) System simplifies the choice

of surfactants to meet emulsion formulation requirements. It is based on the

balance between the hydrophilic and the lipophilic proportions that give each

surfactant its functionality. In the HLB System, the hydrophilic-lipophilic

balance of each surfactant has an HLB number. Each oil or wax to be emulsified

has a required HLB number, indicating the surfactant HLB required to give a

satisfactory emulsion. By choosing surfactants with HLB values appropriate for

emulsifying any given oil system, trial and error effort is reduced and optimum

performance is usually obtained rapidly. Emulsifier combinations in the HLB

range of 8 to 18 prove most suitable for oil in water products. Water in oil

emulsions generally requires emulsifiers in the HLB range of 4 to 6.

Generally, the lower the HLB value, the more lipophilic the surfactant;

conversely, the higher the HLB value, the more hydrophilic. For example,

surfactants with an HLB of 4 to 6 are considered lipophilic and tend to form

water-in-oil emulsions. Surfactants in the range of 8 to 18 are considered

hydrophilic and tend to form oil-in-water emulsions. In general:

Application HLB Range

Water in oil emulsifiers 4-6


Hydrophile-Lipophile-Balance


Welting agents 7-9

Oil in water emulsifiers 8 8-18

Detergents 13 13-15

Solubilizers 10 10-18

Hydrophilic surfactants (relatively high HLB value) - are water-soluble and

are used for solubilization, detergency (when almost completely water-soluble),

and for products which readily dilute with water.

Lipophilic surfactants (relatively low HLB value) - are used to couple water-

soluble materials into a non aqueous oil-based system.

Fig: HLB scale designed by Griffin

Apparatus: - Round bottom flask, burette, burette stand, water bath, condenser, pipette

etc.

Chemicals: - Alcoholic KOH, N/2 HCL, N/10 NaOH, Phenolphthalein, GMS, Stearic

acid etc.

Procedure:-

Part (A) – Determination of Saponification Value


(Definition – It is the number of milligrams of KOH required to saponify 1 gram

of given ester)

i) Prepare 0.5 N alcoholic KOH, 0.5 N HCl and 0.1 N NaOH solutions.

ii) Add 0.5 grams of glyceryl mono stearate (GMS) in round bottom flask

containing 25 ml alcoholic KOH and then reflux the mixture for about 1

hour.

iii) Carry out blank determination with similar manner without sample.

iv) Cool both the mixtures to room temperature and titrate against 0.5 N HCl

solution using phenolphthalein as an indicator.

v) Note down the readings, One with sample (a) and another without sample

(b).

Part (B) – Determination of Acid value

(Definition – It is the number of milligrams of KOH required to completely

neutralize 1 gram of free acid in sample)

i) Weigh accurately 0.5 grams of Stearic acid, add it into conical flask

containing 10 ml alcohol and 10 ml ether.

ii) Warm the mixture on water bath if required.

iii) Cool the mixture and titrate against 0.1 N NaOH using phenolphthalein as

an indicator.

iv) Let the reading will be (c) ml

Calculations:-

(A) – Saponification Value

Factor – 1000 ml of 1 N KOH = 56000 mg of KOH

(b-a) of 0.5 N KOH = X

X = (b-a) X 0.5 X 56000

1000

Therefore,

X = ---------------- / 0.5 grams of NaOH

Hence,

For 0.5 grams of NaOH = X

For 1 grams of NaOH = S

(Cross multiplication)


Therefore,

Saponication value (S) = -------- mg of KOH/ 1 gram of sample

(B) – Acid Value

Factor – C ml of 0.1 N NaOH = 0.5 gram of sample

2 X C ml of 0.1 N NaOH = 1 gram of sample

(2 X C ml) of 0.1 N NaOH = 1 gram of sample

1000 ml of 1 N NaOH = 56000 mg of KOH

1000 ml of 0.1 N NaOH = X


X = -------

Therefore,

For 1000 ml = X

For C ml = A


A = ------- mg KOH

Therefore,

Acid value (A) = -------- mg of KOH/ 1 gram of sample

(C) – HLB Value

HLB Value = 20 X 1 - S/A

Therefore, HLB value of GMS = --------------


Result:-

The Hydrophile-Lipophile-Balance (HLB) value for Glyceryl Mono Stearate

was found to be ------------

Answer the following question:

1. Write importance of HLB determination

2. Define Acid value and Saponification value


Aim- To study calibration and weights

References-1)V. Alexeyev. A Textbook of Quantitative Analysis, Foreign Languages

publishing House. P. No 39-41.

Theory- Although analyses of weights are made to a high degree of precision, their

actual weight may vary. Therefore weights must be checked or calibrated time to time.

It can be shown that difference in weights between tested weight and rider in mg is

P1 - P2 = ½ (L2 - L1) s……………………………………………………….(1)

s- Value of scale division

Result – Calibration and weights is studied as per protocol


Calibration and Weights


Aim- To study calibration and weights

References-1)V. Alexeyev. A Textbook of Quantitative Analysis, Foreign Languages

publishing House. P. No 39-41.

Theory- Although analyses of weights are made to a high degree of precision, their

actual weight may vary. Therefore weights must be checked or calibrated time to time.

It can be shown that difference in weights between tested weight and rider in mg is

P1 - P2 = ½ (L2 - L1) s……………………………………………………….(1)

s- Value of scale division

Result – Calibration and weights are studied as per protocol


Calibration and Weights


Aim- Calibration of volumetric apparatus like, Pipette burette etc.

References- 1) V. Alexeyev. A Textbook of Quantitative Analysis, Foreign Languages

publishing House. P. No-

Procedure:

1. It is necessary to determine the true volume of the pipette you will use in this

experiment. To calibrate your pipet, weigh a small, clean flask or beaker as accurately

as possible. Handle the container with a Kim wipe to avoid contaminating it with oil or

moisture from your skin. Record the mass of the container on the data sheet.

2. Carefully fill the pipet, adjust the water to the line, and transfer the contents to

the container. Make sure you know whether the last bit of water should be removed

from the pipet. Weigh the container and the water. Record the value in the data table.

3. Repeat the procedure two more times.

4. Since the density of water varies with temperature, measure the temperature of

the water that you used. Refer to the following table to find the density of the water.

Record the value in the data table.

Temp. C Density

g/mL Temp. C Density

g/mL

18 0.9986 22 0.9978

19 0.9984 23 0.9976

20 0.9982 24 0.9973

21 0.9980 25 0.9971

5. Using the mass of water in the sample and the density of the sample, calculate

the volume of the sample and thus the volume of the pipet.

6. Select an unknown liquid and record its number or letter on your data sheet.

7. Weigh a clean, dry container as you did earlier in the experiment. Record the

value in the data table.


Calibration of volumetric apparatus Pipette


8. A common technique to remove traces of a liquid from a container is to rinse

the container several times with the new liquid that will be used. Draw several portions

of the unknown into the pipet, rinse, and discard.

9. Fill the pipet to the line, and transfer the liquid to the pre-weighed container.

Record the mass of the container and liquid in the data table.

10. Repeat the procedure two more times. Discard the unknown liquid as directed

by your instructor.

11. Using the calculated volume of the pipet (from Step 5) and the mass of the

unknown sample, determine the density of the unknown.

Observation Table:-

Trial 1 Trial 2 Trial 3

Mass of container & water

Mass of empty container

Mass of water

Temp. of water

Volume of water

True volume of pipet

Average value for volume of pipet ________________

(Use this value for future calculations)

Density of Unknown Liquid

Trial 1 Trial 2 Trial 3

Mass of container & unknown

Mass of empty container

Mass of unknown

Volume of pipet

Density

Unknown Number _______________

Average value for density _________________


Aim- Preparation and standardization Bases (NaOH).

References-1)Indian Pharmacopoeia, 2007, volume 1, Government of India Ministry of

Health and Family Welfare, published by Indian Pharmacopoeia Commission,

Ghaziabad, p.552

Preparation of Sodium Hydroxide, 1 M:Dissolve 42 g of sodium hydroxidein

sufficient carbon dioxide-free water to produce 1000 ml.

Standardization Procedure-Weigh accurately about 5 g of potassium hydrogen

phthalate,

Previously powdered and dried at 120° for 2 hours, anddissolve in 75 ml of carbon

dioxide-free water. Add 0.1 ml ofphenolphthalein solution and titrate with the sodium

hydroxide solution until a permanent pink colour is produced.

1 ml of 1 M sodium hydroxide is equivalent to 0.2042 g ofC8H5KO4.

Result – NaOH (strong base) was prepared and standerdised as per Indian

pharmacopoeia


Preparation and Standardization of Bases (NaOH).


Aim- Preparation and standardization of acids (HCl).

References- 1)Indian Pharmacopoeia, 2007, volume 1, Government of India Ministry

of Health and Family Welfare, published by Indian Pharmacopoeia Commision,

Gaziabad, p.550

Procedure:-

Preparation of Hydrochloric Acid, 1 M: Dilute 85 ml of hydrochloric acid with

water to produce 1000 ml. Standardise the solution in the following manner.

Standardization Procedure-Weigh accurately about 1.5 g of anhydrous sodium

carbonate, previously heated at about 270º for 1 hour. Dissolve it in 100 ml of water

and add 0.1 ml of methyl red solution. Add the acid slowly from a burette, with

constant stirring, until the solution becomes faintly pink. Heat the solution to boiling,

cool and continue the titration. Heat again to boiling and titrate further as necessary

until the faint pink colour is no longer affected by continued boiling.

1 ml of 1 M hydrochloric acid is equivalent to 0.05299 g of Na2CO3.

Result – HCl (strong acid) was prepared and standerdised as per Indian

pharmacopoeia


Preparation and Standardization of Acid (HCl).

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