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Experiment-5 To determine the specific rotation of the cane sugar solution with the help of Bi-quartz or Laurent helf shade polarimeter.
Apparatus used: Polarimeter, balance, measuring cylinder, beabar, light source.

Formula used:
The specific rotation of the plane of polarization of the sugar dissolved in water can be determined as:
Laurent Polarimeter


S =       θ    
l x c
      θ xV   
l x m
   cm 3
dm.gm
   (centimeter )3   
decimeter.gram
=
 

Where;
θ= rotation produced in degree
L =  length of the tube in decimeter
m = mass of the sugar dissolved in gram.
V = volume of the sugar solution.

  1  
Observation: Least count of the polarimater  =
= 0.1
  10  





Table1: For Distilled water

First position of Analyser

Position 180o apart

← Clockwise →

← Anticlockwise →

← Clockwise →

← Anticlockwise →

M.S.

V.S.

Total

M.S.

V.S.

Total

M.S.

V.S

Total

M.S.

V.S.

Total

 

 

θ1

 

 

θ2

 

 

θ3

 

 

θ4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Table 2: For Sugar solution

 

First position of Analyser

Position 180o apart

Concentration

← Clockwise →

← Anticlockwise →

← Clockwise →

← Anticlockwise →

M.S.

V.S.

Total

M.S.

V.S.

Total

M.S.

V.S

Total

M.S.

V.S.

Total

 

 

 

θ1

 

 

θ2

 

 

θ3

 

 

θ4

 

 

 

 

 

 

 

 

 

 

 

 

 

2.5%

 

 

 

 

 

 

 

 

 

 

 

 

5%

 

 

 

 

 

 

 

 

 

 

 

 

10%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Calculations:

 
For sugar solution (2.5%) θ1 = (θ1 from sugar solution – θ1 from distilled water)
θ2 =
  θ3 =
  c =   m s1 + s2 + s3+ s4

   v
  θ1= θ1 +θ2+θ3+θ4 ; s1=       θ    
l x c
=     θ    
l x c
x    100    
    2.5

4
For sugar solution
(5%)
θ2 =   s2                
10 % θ3 =     s3   (centimeter) 3    

dm.gm
  Mean S = s1 + s2 + s3  

3
Results = Specific Rotation of the cane Sugar solution is …… cm 3 \ dm-gm
Stadarad Value = 66.5

% error = Standard Value - Experimental Value x 100 = ......... %
Standard Value
Maximum Permissible error:             S=     θ .v    
l x m
   ds    
s  
=    dθ    
θ
+    dv    
v
+    dm    
m
+    dl    
 l
Precautions :  
 
 

 

 
     
 

Question of Answer for viva-voce:-



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