Graduated pipette is a precision liquid measuring instrument. Pay attention to the following points in use:
1. Before use:
① Observe whether the straw is damaged or stained.
② Observe the specification of the pipette: the specification of the pipette used should be equal to or approximately equal to the volume of the solution to be absorbed.
③ Observe whether there is "blowing": if there is, it indicates that the scale reaches the tip. After discharging, blow out the solution at the tip, otherwise do not blow.
2. Holding method: the thumb and middle finger are clamped on the straw, and the index finger is free.
3. Liquid taking: ① enter the liquid vertically; ② the depth of liquid entering is moderate; ③ the ear washing ball absorbs the liquid; ④ the liquid taking height is 2-3cm higher than the scale; ⑤ press the suction tube tightly with the index finger
⑥ lift the graduated pipette from the liquid level at the upper end ⑦ observe that there are no bubbles in the liquid ⑧ wipe the pipe wall with filter paper.
4. Discharge liquid to the scale: ① the scale pipette is vertical ② the right eye is parallel to the scale line ③ gently loosen the index finger (rotate the scale pipette) to slowly reduce the liquid level until the lowest point is tangent to the scale line.
5. Put the liquid into the container: ① the scale pipette is vertical ② the container is inclined at 45 ℃ ③make the solution flow into the container naturally, and pay attention to blowing or not blowing.
6. A pipette absorbs only one reagent and immerses it in water immediately after use