Preparation before burette use

1. Check the leakage test

After the burette is washed, first check whether the stopcock rotates flexibly and whether there is any water leakage. First close the stopcock, fill the burette with water, and check with filter paper around the stopcock and at the tip of the tube. Then rotate the stopcock 180 degrees, stand upright for two minutes, and check with filter paper. If water leaks, acid pipes are coated with petroleum jelly; Before using the basic burette, check whether the rubber tube is aging, check whether the glass beads are of appropriate size, and if there is a problem, replace the piston in time to apply petroleum jelly.

2. Washing of burettes

The burette must be washed before use, in such a way as not to damage the inner wall. Before washing, close the stopcock, pour about 10mL of wash, open the stopcock, release a small amount of washer to wash the tip of the tube, and then tilt towards the nozzle while turning to fill the whole tube. Finally, it is released from the nozzle of the tube (it can also be soaked in chromium pickling solution). Then rinse with tap water. Wash three times with distilled water, 10~15mL each time.

The washing method of basic burettes is different from acid burettes, which can remove the tip of the tube and glass beads and put them into the washing solution for immersion. The tube body is upside down into the wash, and the washing solution is sucked up with an ear suction ball.

3. Rinse

The burette must also be rinsed with the operating solution three times before use, 10~15mL each time. Discard the lotion.

4. Fill the liquid to drain the bubbles

After washing, inject the operating solution above the neutral line and check for air bubbles around the piston. If so, open the piston to flush out the solution and expel the air bubbles. Titrant loading must be injected directly and cannot be assisted by funnels or other vessels.

The method of draining bubbles from the basic burette: put the basic burette tube body upright, pinch the glass bead with the left thumb, bend the rubber tube, the tip of the tube is obliquely upward about 45 degrees, squeeze the hose at the glass bead, and make the solution flush out to exclude the bubbles.

5. Read the first reading

After the solution is released (after filling or titration), wait one to two minutes before reading. To read, remove the burette from the burette holder and pinch the upper liquid-free area with your left hand, keeping the burette vertical. The line of sight is tangent to the horizontal line of the scale at the lowest point of the meniscus. If the line of sight is above the meniscus, the reading will be high; Below the meniscus, the reading will be low. If it is a colored solution and its meniscus surface is not clear enough, the highest point of the liquid level is read. Generally, the initial reading is either 0.00 or 0~1mL on any scale to reduce the volume error.

Some burettes have a blue band on the back called a blue ribbon burette. Le Cordon Bleu burette readings are similar to normal burettes, when Le Cordon Bleu burette contains solution, two meniscus surfaces intersect, and this intersection point is the position of the Le Cordon Bleu burette reading.