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Water - Solubility - Ions

Instrumental Methods
Infra-red Spectroscopy - Identifying Compounds.

Infra-red light is absorbed in a substance by vibrating atoms.

The frequency of the absorbed light
is the same as the frequency at which the atoms vibrate.
The frequency at which the atoms vibrate depends on
the mass of the particular atom and the next atom it is joined to.
For example a carbon atom joined to another carbon atom  C - C
will vibrate at a different frequency from
a carbon atom joined to a hydrogen atom  C - H.

In infra-red spectroscopy all of the different frequencies of
infra-red light are passed through a substance
and the instrument produces an infra-red spectrum
showing peaks where the light has been absorbed.


The substance is identified by a computer
which compares the shape of the infra-red spectrum
with the spectrum of thousands of known materials.
The area of the peak shows the concentration of the substance
(how much is present).

Infra-red spectroscopy can identify biological compounds
and may be used by the health service and drug companies.

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