The VEE GEE Model C10 Abbe Refractometer is an excellent instrument for the Refractive Index (nD) analysis of liquids, glass, plastic, & film. Easy to Use. Operation consists of placing a sample on the prism; while looking through the eyepiece, the control knob is turned until the shadowline is centered in the crosshairs; the reading is taken where the vertical line crosses the scale. Calibrates with water. Industrial Features. Oversized, easy-to-read scale; Refractive Index (nD) & Brix scales; primary & secondary prisms; color compensator dial.