Bellingham and Stanley Abbe 60, Руководство пользователя, Страница: 23 / 26

Funnel Flowcell
Attaching the flowcell to the prism box.
•
Remove the two hexagon headed bolts securing
the prism box hinge to the lower prism box and
completely remove the upper prism box.
• Remove the two countersunk screws from either
side of the toggle fastener and detach fastener.
•
Fit two angle brackets provided with the flow-cell
to either side of the prism plate using the screws
provided with the flowcell.
•
Check that the silicon rubber gasket is fitted in the
flowcell with the rectangular aperture allowing
unrestricted flow through the two inlet and outlet
holes.
•
Fit the flowcell to the brackets, tightening the two
knurled screws together to ensure that the
flowcell sits parallel to the prism plate and the seal
is uniformly compressed.
Filling the flowcell
The cell is provided with a filling funnel and a drain tube with antisyphon tube. This prevents the cell
being drained by syphonic action in use. Place an empty beaker below the drain tube and pour in
about 50 ml of distilled water into the funnel. Check for any leaks around the base of the flow cell.
If any appear, check the tightening of the clamp screws and, if necessary, remove the cell and
reseat.
The light source must be critically adjusted for the flow
cell since the aperture is restricted and it is essential that
the source is in the correct position. There is a recessed
window for the admission of illumination between the
two water jacket nipples. The light source must be
adjusted to the same height as this aperture.
The control knob is now used to set the scale to the
correct reading for water, taking the temperature into
account (1.3330 at 20
°
C). The borderline will be
appear as an illuminated band across the crosswires. It is the lower edge of the band that is of
importance. (Direct Reading models only: any colour at the edges of the band should be cleared by
rotating the dispersion control.) The upper edge of the illuminated band is formed by a cut off by
the cell entrance aperture and is thus out of focus and may be diffused. The lower edge, however,
should be sharply defined and free from colour and is to be used in all measurements.
It is possible that the lower (borderline) edge is not in coincidence with the crosswire intersection,
this being due to a physical displacement of the prism plate caused by the pressure of the flow cell.
This is of no consequence and only requires an adjustment to the zero as detailed in Section 3.
Care must be taken in the use of the flow cell to avoid air pockets becoming trapped in the
chamber. If this occurs, impairing definition, the instrument should be slightly inclined to attract the
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