The use of glass instruments commonly used in burettes

Burettes are volumetric instruments designed to dispense an indeterminate amount of liquid.

1. Classification:

Acid burette (holding acidic, neutral, oxidizing solutions), basic burette (holding lye)

2. Use: washing, oiling, leak testing, rinsing, liquid filling, exhausting

Washing: For burettes with no obvious oil stains, rinse them directly with tap water. If there is oil stain, wash with chromic acid lotion.

When washing the alkaline burette, be careful not to let the chromic acid lotion directly contact the rubber tube.

Oiling: Wipe the piston and plug seat with filter paper, dip a small amount of Vaseline with your fingers, and apply a thin layer to both ends of the piston. Insert the piston vertically into the plug seat and make a circular motion in the same direction until the Vaseline is uniform and transparent when viewed from the outside. If too much oil is applied, it is easy to block the tip of the outlet pipe. You can fill the whole pipe with water first, and immerse the outlet end in hot water. After a while of temperature and humidity, open the piston, so that the water flow in the pipe suddenly flows out, and the melted grease is brought out. .

Leak test: The burette must be checked before use to ensure that it does not leak. Fill the acid burette with distilled water, clamp it vertically on the titration stand, and leave it for 5 minutes. Observe whether there are water droplets dripping from the tip of the tube, and whether there is water seepage at the gap of the piston. Observe once. The basic burette only needs to be filled with distilled water, clamped vertically on the titration rack, placed for 5 minutes, and then observe whether there are water droplets at the tip of the tube.

Exhaust: use the right hand to hold the upper part of the acid burette without scale, the burette is inclined about 30°, and the left hand quickly opens the piston to flush out the solution. If there are still air bubbles, repeat the operation several times. If there is still a possibility that the outlet pipe is not clean , need to be rewashed.

Clamp the basic burette vertically on the titration rack, bend the rubber tube upward, and the outlet tube is inclined upward, gently squeeze the rubber tube to the side, so that the solution is ejected from the mouth of the tube to discharge air bubbles.