Lift the cover and wipe the surface of the cover and prism with a soft velvet cloth; drop the liquid to be tested on the surface of the prism with a straw, close the cover and press it gently, point the refractometer to a bright place, rotate the eyepiece to make the field of view The inner scale line is clear, just read the value of the light-dark dividing line on the corresponding scale on the labeling board; after the test, wipe the surface of the prism and the cover with a flannel, clean the straw, and put the instrument in the box.
