22
7. Calibration (Scale adjustment)
Since monobromonaphthalene is very corrosive liquid, wipe it off put of the test piece
and prism surface with gauze or tissues moistened with alcohol immediately after
calibration is complete. If there is a very small amount of monobromonaphthalene left
on the main prism, the prism surface is seriously stained within 24 hours and the prism
may become incapable of measurement with unclear boundary line. If it is left for a
considerably long time, the prism becomes useless. Such stain results from minute
corrosion on the prism surface. At a glance the prism surface looks clean, but it is
actually stained in rainbow-color or faintly clouded, which can be seen when it is
observed at a low angle. If such the surface is observed in magnification, it is uneven
because of minute corrosions. Such corroded surface is worse than the surface having
one or two scratches.
When handing monobromonaphthalene, pay careful attention to its highly corrosive
characteristic and carefully clean the applied area after use.
ە
Cautions on use of monobromonaphthalene
The Safety Data Sheet (SDS) for monobromonaphthalene says that it may irritate the
skin and the eyes. Although the harmful effect of monobromonaphthalene is not likely to
occur under the ordinary circumstances as the amount used in one measurement is
less than 0.1ml, be sure to wear gloves and masks and take other safety measures with
due caution when measuring a sample.
Again turn the measurement knob to
adjust the scale indication so that it
corresponds to the Refractive Index
shown on the test piece. Then, adjust
the calibration screw located in the
center of the calibration section with a
screwdriver so that the boundary line
appearing in the field of refraction meets
the intersection of the cross hairs (Fig.
7-6).
Remove the test piece and clean the
surface of both the main prism and test
piece with alcohol, etc. Set the test
piece on the main prism for measuring it
again and check to see if the measured
value is equal to the known Refractive
Index of the test piece.
h)
i)
When the refraction view is not
clear
because
of
intense
illumination of the lamp, shake the
light with white thin paper or tissue
paper by inserting it between the
lamp and test piece.
Note:
Fig. 7-6
