T/AHEMA 13-2022 Active

Main Technical Content: 8. Titration Operation and Zero Adjustment - If the liquid level in the titration pipette is below the "0" mark, add solution until it reaches a few millimeters above the "0" mark. Hold the pipette vertically on the right side of the titration stand. After 30 seconds, adjust the zero point and remove any droplets hanging from the pipette tip. Record the initial reading. - For pipettes with stopcocks: - Insert the tip of the pipette into the conical flask opening approximately 1–2 cm deep. - Bend the left ring and little fingers toward the palm, gently pressing against the outlet tube with the thumb and index finger. - Gently twist the stopcock to release the solution steadily. - Do not release the stopcock during titration. - For pipettes without stopcocks: - Insert the tip of the pipette into the conical flask opening approximately 1–2 cm deep. - Clamp the outlet tube with the left ring and little fingers. - Use the thumb and index finger to squeeze the latex tube toward the glass bead to release the solution. - Release the thumb and index finger first, then the ring and little fingers. - For observing the color change at the titration endpoint, place white paper or a white board on the titration stand surface to ensure adequate lighting. - Use a fluorescent lamp as supplementary lighting if natural light is dim. - Follow relevant standards for lighting requirements. - Start titration by shaking the conical flask and titrating simultaneously, selecting an appropriate titration rate based on the reaction type. - Avoid contact between the conical flask and the pipette. Shake the flask in a circular motion toward the same direction, with consistent and moderate shaking intensity. - As the endpoint approaches, add one drop of solution at a time and shake after each addition until the standard-defined endpoint is reached. - To add half a drop: - Hang the solution at the tip