4
Where, L is the length of test solution (optical tube), with mm as unit; C is the concentration of the
optically active substance in the test solution. The instrument typically shows the result in the
grams of optically active substance in per 100mL solution.
If the specific rotation [
α
]
t
λ
of test substance is known in advance, the optical rotation
α
t
λ
is
measured at certain temperature and wavelength, the length of the test solution is L, the
concentration of optically active substances in solution (C) can be calculated with the formula (2)
C=
α
t
λ
/[
α
]
t
λ
·L (2)
If the solution contains a non-optically active, other than the optically substance, with
concentration of prepared solution and formula (2), the concentration of the optically active
substance (C) can be obtained, and the content of an optically active substance or purity can be
calculated.
3.2 Optical Zero Principle
If the natural light goes through the polarizer and the sequence analyzer in order, use the
orthogonal point of the light direction of a polarizer and an analyzer as zero. According to the law of
Marius, the relationship between the angle which deviates from the quadrature position of the
analyzer (
α
) and the intensity of the incident light of the analyzer (I):
I=I
0
COS
2
α
As shown in Figure 1,
