Refractormetery

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Aim:-

 To determine the specific and molar refractivity of pure organic liquids by Abbe’s refractor meter.

 

Apparatus:-

Abbe’s Refractor meter, Dropper, cotton, specific gravity bottle.

Chemicals: - Benzene, Acetone, Carbon tetrachloride.

 

Theory: -

When a beam of light passes from one medium to another it suffers refraction i.e. changes its direction. If passes from a less dense (Air) to a more dense medium (liquid) it refracts towards the normal.

The refractive index of the second medium with respect to the first medium is given by the formula.

Sini/sinr= pi = Refractive index.

Specific refractivity is determined by

r=n2-1/n2+2 *1/d.

r=Specific refractivity.

d=Density of liquid.

m= molecular weight of the medium.

 

Procedure:-

1)  Refractometer on the table near a window so that sufficient light-reactive to the prism.

2)  Open the prism box by refreshing the lock net clean the faces of both prisms with the help of cotton dipped in acetone allow the surface to dry up.

3)  Place few drops of liquid under examination carefully and close the prism.

4)  Focus the cross wire of telescope by rotating the eye peace and adjust the mirror to reflect maximum light into the prism box.

5)  Move the prism box backward and forward until a clean boundary between light and the dark region appears.

6)  Now rotate the prism box until the sharp boundaries line coincides with the intersection of the cross wire of the telescope.

7)  Read the refractive index directly on the scale repeat reading at least three times and take the mean.

8)  Determine the density of liquid by using a density bottle and record the observation.


Calculation of density:-  

1)  Weight if the empty specific gravity bottle W1=…………

2)  Weight if the empty specific gravity bottle + liquid

       W2A= ……….

       W2B=………..

3)  Weight of the empty specific gravity bottle + water W3=………

4)  Weight of the specific gravity bottle W1=….

5)  Weight of distilling water = W3-W1

6)  weight of liquid A= W2A-W1

 

7)  Density of liquid A= d = weight of liquid A/weight of water.

 

8)  Weight of liquid B  =  W2B-W1

 

9)  Density of liquid B= d = Weight of liquid B/Weight of water.


Tabular column

Liquid

Density

Refractive index

R=n2-1/n2+2 *1/d

R=n2-1/n2+2 *1/d

 

 

 

 

 

 

 

 

 

 

 

 

Result:-

1)  Specific Refractivity of liquid A = RA= ______

2)  Specific Refractivity of liquid B =RB

= _______

3)  Molar Refractivity of liquid A =RmA= _______

4)  Molar Refractivity of liquid B= RmB = _______

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