26
9. Measurement of solid sample
Note:
(1)-2 Choosing contact liquid
For measuring a solid sample, it is
required to use contact liquid
proper to the sample to make close
contact between the sample and
the prism. The Refractive Index of
contact liquid must be higher than
that of the sample.
For example, the following solutions
are generally used as contact liquids.
Methyl salicylate
Monobromonaphthalene
Methylene iodide
Methylene iodide containing
sulfur solution
(depending on sulfur concentration)
Since all of the above-mentioned
solutions have the highly corrosive
characteristic, choose a proper
solution that is comparatively weak
in corroding the sample.
20
D
20
D
20
D
n
ࠉҸ
1.53
n
ࠉҸ
1.65
n
ࠉҸ
1.74
n
ࠉҸ
1.74 to 1.78
20
D
(1)-3 Mounting sample on main
prism
As shown in Fig. 9-2, a solid
sample must be put on proper
contact liquid dript on the main
prism.
Cautions on mounting sample
Wipe down the upper surface of
the main prism before dripping
contact liquid onto it.
Put a tiny quantity of contact liquid
on the center of the prism.
In the case of a glossy and flat
glass sample, put a tiny quantity of
contact liquid on the center of the
glass surface to contact the prism.
One drop of 1mm in diameter is a
proper quantity.
ە
ە
If there are burrs on the sample
such as cut plastic plate, etc., it
cannot contact the prism surface
well. In case of such samples,
completely remove burrs out of
the contact side and carefully
polish it.
Fig. 9-2
Lighting side
Sample
Contact surface
Contact liquid
Light
Main prism
