Saccharimetry

Digital saccharimeter (2004),
Zucker-Museum Berlin

Under saccharimetry derived from saccharide , the chemical term for sugar , is meant a polarimetric determination of the concentration of aqueous sugar solutions .

The measuring process is based on the fact that certain substances, such as most sugar or lactic acid , when dissolved in water, have an optical rotation capacity; they are optically active . This is expressed by the fact that linearly polarized light rotates its plane of polarization as it passes through the solution. This rotation is proportional to the concentration of the substance and the length of the light path through the solution: ${\displaystyle \alpha }$ ${\displaystyle c}$ ${\displaystyle l}$

${\displaystyle \alpha =\alpha _{0}\cdot c\cdot l}$

Here is or also a material constant , namely the specific angle of rotation . It depends on the measurement conditions (including measurement temperature and wavelength of the light used), which is why, strictly speaking, they belong to every specification of a specific angle of rotation: ${\displaystyle \alpha _{0}}$ ${\displaystyle a}$

${\displaystyle \left[\alpha _{0}\right]_{\lambda }^{T}=...}$

Normally the specific angle of rotation is given for yellow sodium light ( λ = 589 nm or "D" for the sodium D-line ) and a temperature of 20 ° C (or 25 ° C):

${\displaystyle \left[\alpha _{0}\right]_{D}^{20}=...}$

If you put an optically active substance into a polarimeter of a given dimension, you can determine the concentration by measuring the angle of rotation.

The reverse case, i.e. H. the determination of the material constants is also possible, since all three quantities can be determined experimentally quite easily and absolutely precisely.

See also

• Saccharimeter (very similar word, but for a different measuring principle)

literature

• Wilhelm Walcher : Physics internship . 9th edition. Vieweg + Teubner Verlag, 2006, ISBN 978-3-8351-0046-6 .

Individual evidence

1. ^ Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, p. 1220.
2. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 4: M-Pk. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1985, ISBN 3-440-04514-5 , pp. 2905-2912.
3. ↑ Klaus Schwetlick: Organikum , Wiley-VCH Verlag GmbH, 23rd edition, 2009, pp. 82-83, ISBN 978-3-527-32292-3 .