Name: D.O.E

Section: D.O.S

Class Roll No: Stream:

University Roll No:

DETERMINATION OF PERCENTAGE COMPOSITION

OF SUGAR SOLUTION FROM VISCOSITY

THEORY: The coefficient of viscosity (η) of a liquid is defined as the tangential

force per unit area required maintaining unit velocity gradient between two successive

layers of a liquid, which are unit distance apart from each other .The unit of co-

efficient of viscosity is dyne-sec\cm2 (poise). The co-efficient of viscosity of liquid

can be determined by comparing its coefficient of viscosity with the known

coefficient of viscosity of a liquid. Generally water is taken as the known liquid for

comparison. As this method requires the comparison with another liquid, it is a

relative method.

In relative method for determination of coefficient of viscosity (η) of a liquid,

Poiseuille’s equation can be used. Poiseuille’s equation

η =πPr4t\8vl…………. (1)

Where v=volume of the liquid following through a capillary tube of length (l) in‘t’

sec. The radius of the tube is ‘r’ cm and ‘P’ is the driving pressure in dyne\cm2. P can

be replaced by hρg, where h= difference in height between the levels of the liquid in

the two limbs, g= acceleration due to gravity and ρ is the density of the liquid. Now if

the same capillary and the same volume of liquids are used, then for the two liquids

the following equation can be deduced.

η1\η2=ρ1t1\ρ2t2 …………….. (2)

Where, ρ1 and ρ2 are the densities and t1 and t2 are time of flow for the two liquids. So

if η2 is known, then by determining t1and t2 ,ρ1 and ρ2 , η1 can be calculated.

η1=η2 x ρ1t1\ρ2t2 ……………… (3)

In the present study we are measuring the relative viscosity in comparison of viscosity

of water. So as η2 the viscosity of water and it’s density (ρ2) is known (from the

chart), then by measuring t2 it’s time of flow and ρ1, t1 the density and time of flow of

other liquids, viscosity can be calculated. Times of flow of the liquids are determined

using Oswald’s viscometer and stopwatch. Densities are determined using specific

gravity bottle.

The density of water varies from 0.99987 to 0.98807 gm/c.c in the temperature range

00C to 50

0C and can be taken as 1 gm/c.c , the equation then becomes

η1 = η2 x ρ1t1\ t2 centipoise ……………(4).

PROCEDURE:

1. Determination of density of liquid using specific gravity bottle:

The specific gravity bottle is cleaned, dried and weighed empty. Then it is filled with

water and weighed. Then the bottle is filled with stock solution and then unknown

solution and weighed. The densities of other solutions are then determined by

calculations.

2. The time of flow of same volume of each liquid is determined using an Ostwald’s

Viscometer. The time of flow of same volume of water is determined using same

Viscometer. The data thus collected is put into the equation (4) which is the working

formula.

3. Preparation of solution:

Stock solution: 10% sugar solution is prepared at first. Then 6% and 3%solution are

prepared from the stock solution in the following way.

% of solution Volume of stock

solution

Volume of Water Total volume

of solution

6% 18c.c 12c.c 30c.c

3% 9c.c 21c.c 30c.c

4. Graph:

Coefficient of viscosity of each solution is plotted against conc. of each solution.

From the graph, conc. of unknown solution can be determined

Coefficient

of viscosity(η)

unknown

conc. of sugar solution (%)

RESULT:

1. Recording of temperature:

Initial temperature(0C)

Final temperature(0C)

Mean temperature(0C)

2. Preparation of solution:

% of solution Volume of stock

solution

(ml)

Volume of Water

(ml)

Total volume

of solution

(ml)

3. Recording of weight for determination of densities:

Wt. of empty

bottle with lid

(gm) x

Wt. of bottle with lid

+

Wt. of water

(gm) y

Wt. of unknown

solution + Wt. of

bottle with lid

(gm) p

Wt. of 10% solution+

wt. of bottle with lid

(gm) z

4. Recording of time flow

% of solution Time of flow

(sec)

Mean time

(sec)

Water

i)

ii)

3% i)

ii)

6%

i)

ii)

Unknown

i)

ii)

10% i)

ii)

5. Determination of coefficient of viscosity of each solution using equation (4)

% of solution Density (gm/c.c.) Coefficient of viscosity(centipoises)

Water

10%

6%

3%

Unknown

Calculation:

Wt. of water=(y-x) gm=……………………gm

Wt. of 10% solution= (z-x) =…………………gm

Wt. of unknown solution= (p-x) =…………………gm

Density of 10% solution (q) = (z-x)\(y-x) x Dw=…………….. gm\ml

Density of unknown solution(r) = (p-x)\(y-x)xDw=……………….. gm\ml

Density of 6% solution= (18xq+12xDw)\30=s gm\ml=………………… gm\ml

Density of 3% solution= (9xq+21xDw)\30=t gm\ml=………………… gm\ml

10%=w x (q\Dw) x (time of flow of 10% solution\time of flow of water)=a Centipoises

=…………….. centipoises

6%=w x (s\Dw) x (time of flow of 6% solution\time of flow of water) =b centipoises

=……………… centipoises

3%=w x (t/Dw) x (time of flow of 3% solution\time of flow of water) =c centipoises

=……………… centipoises

unknown=w x (r/Dw)x (time of flow of unknown solution\time of flow of water)=d

centipoises=……......... centipoises

DISCUSSION:

The viscosity of a solution depends on the concentration of the solute present in it and also on

the temperature of the solution. So prior to the experiment all the apparatus were well cleaned

with distilled water so that no impurities be present in it. If the temperatures of measurement

are not fixed, the viscosity of the solutions at different temperature will be different. So all

the viscosity measurement of the solutions are performed under same temperature. The

measurement of time flow was done correctly. The viscometer was cleaned after every single

measurement. Exactly same volume of solvent / solution were used in the viscometer, neither

the relative viscosity measured will be erratic. For measurement of densities, the specific

gravity bottle was dried well, filled fully with fluid and lid were introduced. Any error in

measuring weight, the overall experiment will be erratic. So; proper care was taken while

measuring the fluid flow as well as density measurement.

CONCLUSION:

From the graph the concentration of sugar in the supplied unknown sugar solution is found to

be ( ………… ) % at ………………

0C.

CHART Density, viscosity datas of water at different temperature

Temperature( 0C) Density (gm/c.c) Coefficient of

viscosity(centipoise)

0 0.99987 1.787

10 0.99973 1.307

15 0.99913 1.139

20 0.99823 1.002

25 0.99707 0.8904

30 0.99567 0.7974

35 0.99406 0.7194

40 0.99224 0.6529

45 0.99024 0.5960

50 0.98807 0.5468