When titrating, the amount of liquid added does not need to fall exactly on the scale line, as long as the amount of solution can be read correctly. The amount of titration solution used in the experiment is the difference between the amount of liquid in the tube before titration and the amount of liquid in the tube after titration. The bottom switch can effectively control the flow rate of the titrant, so that when titrating *, the titrant can be stopped from flowing into the conical flask below in a timely manner. Quickly add titrant when far from the titration endpoint, saving time required for the experiment. If the burette is not air dried before use, it should be rinsed twice with the titrant to avoid contamination of the titrant by liquid adhering to the tube wall before adding the titrant. Due to the narrow mouth of the burette, it is advisable to fill it carefully when filling the titrant to prevent the titrant from leaking out. If necessary, a funnel can be placed at the top of the pipe mouth to assist in filling. After filling the burette with liquid, there should be no bubbles in the tube. If there are bubbles, gently tap the tube wall with a rubber or other object that will not break the glass to let the bubbles float out of the liquid surface. There may also be air present in the channel of the stopcock switch. In this case, the stopcock should be quickly twisted several times to release the bubbles. The burette should be kept in a vertical position during use and should not be tilted to avoid errors when reading the scale.
Previously, the stopcock used in burettes was made of glass. When storing alkaline titrants, a rubber tube containing a round bead was used to replace the stopcock because it was considered that the glass stopcock would get stuck due to the corrosion of the alkaline solution. As long as you lightly press the side of the round bead with your hand, the titrant can flow out. However, nowadays the stopcock on burettes is made of Teflon, which has good resistance to alkaline liquids. Therefore, even when titrating alkaline liquids, there is no need to use the aforementioned rubber tube stopcock.
Tips for use: Use a base burette and do not press the area below the glass bead, otherwise bubbles may form when releasing your hand.
Tips for using an acid burette: Use your left hand to control the stopcock of the burette and observe the color change of the indicator inside the conical flask with your eyes
Leak detection before use of burette: Add an appropriate amount of water to the burette, fix it on the iron frame with a burette clamp, and observe if there is any leakage. If there is no leakage, rotate the piston 180 degrees for acid burette? Gently squeeze the glass ball with a basic burette, release a small amount of liquid, and observe again whether the burette leaks water.
Before use, remove bubbles: For acid burettes, tilt the burette 30 degrees with your right hand? Left and right, quickly open the piston with your left hand to flush out the solution and fill the outlet tube with the solution; For alkaline burettes: bend the upper rubber tube of the glass bead upwards and squeeze the glass bead.
When reading, hold the upper end of the tube vertically and align the solution surface with the eyes before reading.
