1. SURFACE TENSION OF A LIQUID for 1st semBy
Vinod kumar mulge
Department of chemistry

2. SURFACE TENSION OF A LIQUID
AIM:-To determine surface tension of a given liquid by using Stelagmometer
APPARATUS :-Stelagmometer , Beaker 100ml ,Screw cock ,Rubber tube ,Stand, etc.
THEORY:-Surface tension of a liquid is defined as “the force in dynes acting at right angles along the surface of a liquid 1cm in length (Unit :-In CGS dynes per cm and in SI Newton per meter”.
The weight of a drop falling from capillary depends on the radius of capillary and on the surface tension of liquid.
Weight of a drop =Ƴ x 2πr
If the relative surface tension of the liquid with reference to water is given by
Ƴ1/ Ƴ2 =W1/W2
Instead of finding the weight of drop of liquid and water ,it is more convenient to determine number of drops formed by certain volume of liquid and water .Then average weight of liquid drop is given by W1=vd 1g/n1and for water W2 =vd2g/n2
Hence Ƴ1/ Ƴ2 =n2d1Ƴ2/n1d2
The surface tension of water is known the surface tension of liquid can be calculated

3. PROCEDURE:
Clean the stelagmometer with distilled water , rinse with acetone and dry by using hot air blower .Attach a rubber to at the upper end of the stelagmometer with a screw cock .The stelagmometer is fixed vertically to a stand .Select one mark above and one mark below the bulb .Suck the given liquid into the stelagmometer above the upper mark .Now adjust the screw cock so as to fall the liquid in perfect drops .The number of drops should not be more than 20 per minute .Again suck the liquid above the upper mark and allow the liquid flow .Count the number of drops from liquid level between the upper and lower mark .Record the number of drops .Repeat the procedure for two more time .The liquid is replaced in its bottle.
The Stelagmometer is removed from the stand. Rinsed with acetone and washed with distilled water.
Fix the stelagmometer ton stand as before and determine the number of drops formed by distilled water .Record the number of drops of water formed in flowing between two selected marks.

4. TABULAR COLUMN Surface tension of water Ƴw=71.97 Dynes /cm
Liquid
Density d gm/cc
Number of drops
Surface tension of liquid
Ƴi ={(nwxdl)/(nllxdw)}x Ƴw
Dynes/cm 1 2 3
Mean no. of drops n
Liquid A
Dw=
Water

5. DETERMINATION OF DENSITY
1] WEIGHT OF EMPTY SP. GR. BOTTLE W1= Gms
2] WEIGHT OF SP, GR, WITH LIQUID W2= Gms
3] WEIGHT OF SP. GR. BOTTLE WITH WATER W3= Gms
4] WEIGHT OF LIQUID =W2-W1 Gms
5] WEIGHT OF WATER W3-W1 Gms
DENSITY OF LIQUID d=w2-w1/w3-w1 Gms