Sper Scientific 300006 Refractometer - Salt - Manual (Page 3)

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Operating Procedures
1. With the COVER PLATE open, clean the PRISM
with a soft cloth to avoid scratching the surfaces.
2. Aim the refractometer toward a light source and
rotate the EYEPIECE to obtain the clearest focus.
3. Adjustment of the null (reference point):
A. Open the COVER PLATE.
B. Apply a few drops of pure distilled water onto
the PRISM platform.
C. Close the COVER PLATE.
D. Turn the CALIBRATION SCREW so that the
dark and light boundary line coincides exactly
with the 0% line on the scale.
4. Carefully dry the prism platform and the cover.
5. Place a few drops of the test solution on the prism
and close the COVER PLATE so the solution
spreads evenly on the prism.
6. Aim the front of the refractometer towards the light
source and focus the eyepiece on the boundary
line of the light and dark hemispheres.
7. The boundary line indicates the concentration of
salt in the test sample.
13% Sample 25% Sample
8. After use, clean prisms with a cloth and remove
any residue.
9. At 20°C, the saturation point of salt is indicated by
a line near the top of the scale.
10. The temperature of the null reference liquid should
be at the same temperature as the sample solu-
tion. For variations in temperature the null point
should be adjusted once every 30 minutes.
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