Procedure: 1. Open the cover plate and gently insert the prism with a soft cloth 2. Take a few drops of the solution to be measured, place it on the prism, and gently close the cover plate to avoid bubbles, so that the solution is on the entire surface of the prism 3. Aim the light entrance plate of the instrument at the bright place of the light source, observe the scene through the eyepiece, and turn the eyepiece to adjust the handwheel 4. Make the blue-white dividing line of the field of view clear, and the scale value of the dividing line is the concentration of the solution Calibration: Take a few drops of distilled water, put it on the detection prism, turn the zero adjustment screw, make the position of the dividing line modulate by 0% of the scale, and then wipe the detection prism for detection Notes: 1. In the process of use, you must be careful and Caution, use in strict accordance with the instructions, do not arbitrarily loosen the connecting parts of the instrument, do not collide, and strictly prohibit violent vibration 2. After use, it is strictly forbidden to wash directly in water and wipe with a clean soft cloth, and the optical surface should not be touched or scratched 3. The instrument should be stored in a dry and non-corrosive place 4. Avoid loss of spare parts Packing list 1 * screwdriver 1 cleaning cloth 1 * English instruction manual 1x pipette 1 * refractometer box