1. First, you need to callibrate (even out the shadow line with the zero line) the reticle (the scale). How to do this is by taking drops of distilled water and placing them onto the prism. Enough so that the entire prism is covered. Put the cover plate over it and go up to a light. Looking through the eyepiece up by the light, look on the scale and see if the shadow line is at the zero point. If it is not, use the correcting screw to then put it to zero.
2. Once you have seen it at zero, dry the prism off with a dry cloth.
3. Now you can measure the liquid you want to test. Use the same procedure as from step one with the distilled water and the only difference would be the liquid you want to test and the measurment on the shadow line.
4. Don't forget to record your data!
5. When finished, dry off the prism and anything else needed with a dry cloth. Do NOT wash it! Then carefully put the refractometer back in its case.
