The pictures above are of the actual refractometer you will be using in this experiment. Coincidentally, it is exactly the same instrument featured in the text (p. 799-803).
1. Applying your sample
Pull the lever connected to the light downwards as shown in the picture. Then swing the prism open to the left. At this point it would be wise to double check the area on which your sample is applied to ensure that it is clean. On the window that has been exposed upon swinging the prism open (the window directly in the center of the picture on the right), apply your sample. Make sure the sample covers the ENTIRE window. Partial application will result in an incorrect refractometer reading.
2. Measuring the refractive index
Close the hinged prism and return the light to its original position.
Locate the power/view switch on the left side of the instrument. Turn on the instrument (middle setting). The figure above is a schematic of the switch's different settings. Note that you must manually hold the switch in its lowest setting (view mode) while you record the refractive index.
Now locate the eyepiece at the top of the instrument. Looking in the eyepiece, you will see crosshairs with a shadow covering part of the viewing range.
Using the adjustment knob located on the right side of the refractometer, move the shadow until it intersects the crosshairs as shown above. At this time, hold down the power/view switch. The viewing range will now display a two horizontal scales with a fixed vertical line running down the center. Read the upper scale according to the vertical line. You should be able to read accurately the refractive index up to three decimal places, and estimate the fourth. Record the index of refraction and note the temperature (on the built-in thermometer) at which you took the reading. Adjust the refractive index to the standard 20 degrees Celsius using the formula given in your text.
3. Cleaning up
Turn off the instrument and open the hinged prism. Wipe off your sample with a paper towel or kimwipe. Rinse the area with acetone and wipe it dry with a kimwipe.
