Jeulin Fibroptonic Mode D'emploi page 70

Optics
Fibroptonic
Ref : 202 012
1 Purpose
To approximately determine the concentration of a coloured solution from a standard
solution of known concentration.
2 Experiment no. 24
ENGLISH
FIBROPTONIC
2.1 Equipment:
•
Photoresistor module
•
Ohmmeter
•
Directive source of white light or laser
•
Set of identical glass tanks
•
Different solutions of potassium permanganate of concentrations between 10^-4
and 10^-1 mol/litre.
2.2 Set-up and experiment:
•
Connect the ohmmeter to the black and yellow terminals of the photoresistor.
•
Illuminate the photoresistor with the light beam
•
Place a glass tank filled with a decimolar potassium permanganate solution
(control solution) in the beam; measure the resistance R of the photoresistor
(figure 28).
•
Restart the operation with the other control solutions of up to 10^-4 mol/l. Each
time, check that the tank is perpendicular to the beam (for this, observe the
laser's reflected spot) and that the distance from the source to the photoresistor
is unchanged.
•
Plot the curve of the resistance R in function of the concentration C.
•
Pour the solution whose concentration needs to be determined into the glass
tank, measure R, deduce C from the curve established earlier.
Laser
Figure 28: Determining the concentration of a coloured solution by absorption.
COLORIMETRY
Tank tilled wih a
colored solution
70
SHEET
12
Ohmmeter
Photoresistor