||Open the daylight plate and put several drops of sample on the prism surface. Close the daylight plate so the plate comes into contact with the prism surface. The sample should spread completely over the prism surface. Air bubbles or an insufficient sample will be hard to read. If this occurs, repeat the procedure, applying more of the liquid sample.
||Holding the Aquafauna refractometer by the rubber grip, point the prism
end of the refractometer to a light source and observe the field of view through the eyepiece. Focus the eyepiece by turning the cross-striped
portion of the rubber eyepiece guard either clockwise or counter-clockwise until the scale becomes clearly visible.
||A horizontal boundary line separating the blue field of view (top) and
white field of view (bottom) will appear in the field of vision. Adjust the
angle of unit to the light source until line is sharp and distinct. The values
on the scale are specific gravity and parts per thousand (ppt).
(Note: If line appears diffused, repeat step 1 above as there may be debris and/or and insufficient sample between the prism and daylight plate)