What is the purpose of the Silicon Oil for use with Lab Turbidimeters?

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Document ID TE10277


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Published Date 08/07/2018
What is the purpose of the Silicon Oil for use with Lab Turbidimeters?
Explanation for why the silicon oil is used with the 2100P, 2100Q, 2100N, 2100AN, TL23, TU52.
Turbidity is unique compared to most other tests offered by Hach in that it is a measurement of a physical property of the sample instead of a chemical property. We are measuring how that sample interacts with (scatters) light. Because of this, more so than with other instruments, the sample cell used during the measurement can become an interference, because it too interacts with (scatters) light. The purpose of the Silicon Oil (Product # 126936) is to minimize the impact or interference from the sample cell as best as possible. (This is why Silicon Oil isn't needed with colorimetric tests.)

Imperfections in the surface of the glass are going to be the main sources of light scatter from the cell. This can include chips and scratches in the glass, but also the smoothness/straightness of the glass and variations in thickness. The Silicon oil has the same refractive index as the glass itself and fills in any imperfections and creates a more smooth and even finish on the outside of the glass. The inside of course will have the imperfections filled in with sample, and variation of thickness can be accounted for with cell indexing.

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