1.1 Preparing the Biofilter

1.1.3.b Parameter 2: Salinity

METHOD 2

Another possibility to measure salinity is by the use of a refractometer (QuickTime movie; 5.10MB).
refractometer (Real Player movie)
Principle of the refractometer

Refractometers are instruments used to measure substances dissolved in water and oils.

The refractometer works using the principle of light refraction through liquids. As light passes from air into a liquid it slows down.

This phenomenon is what gives a "bent" look to objects that are partially submerged in water. To put it simply, the more dissolved solids water contains, the slower light travels through it, and the more pronounced the "bending" effect on light.

Refractometers use this principle to determine the amount of dissolved solids in liquids by passing light through a sample and showing the refracted angle on a scale.

The advantage is that the measurement is directly expressed in ppt. So no conversions have to be made.

Screenshot of refractometer.

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