[Music] volumetric pipets are glass or plastic tubes usually between 1 and 100 ml used for accurate measurements volumetric pipets are calibrated to deliver only one specific volume the specifications of a volumetric pipet are usually imprinted on the pipet itself the specifications indicate how much liquid will be transferred if the liquid is drawn up to the calibration line on the neck the temperature at which the calibration was made and whether it is a TD or a TC pipet TD means that the pipet is calibrated to accurately deliver the specified volume of liquid TC means that the pipet is calibrated to contain the specified volume of liquid with no remainders to begin again the pipet should be inspected for cleanliness if water beads up or collects on the inner surface the pipet is not clean follow a cleaning procedure or obtain a clean pipet pour the liquid to be pipetted into a beaker make sure there is sufficient liquid to fill the pipet and to rinse three times using a pipet bulb draw up a small quantity of the liquid to be pipetted and thoroughly rinse the entire interior Surface by Rolling the pipet horizontally with a slight rocking motion drain the rinse liquid into a waist Beaker repeat the rinsing procedure at least two more times using the pipet bulb drop the solution into the pipet until it is filled to about 2 to 3 cm above the graduation Mark remove the bulb and quickly place your forefinger over the top of the pipet stem make certain that there are no air bubbles in the bulk of the liquid or foam at the surface tilt the pipet slightly from the vertical position and wipe the outside of the lower stem with lint-free tissue to remove any adhering liquid hold the pipet vertically with the tip touching the inner wall of a waist vessel and slowly allow the liquid level to drop by slightly decreasing the finger pressure halting further flow when the bottom of the meniscus coincides exactly with the top of the graduation Mark the pipet must be held vertically with the Mark at I level move the pipat to the receiving vessel with the pipet held vertically and the pipet tip touching the wall allow the sample to drain freely once the liquid appears to be completely drained leave the pipet for an additional 5 Seconds by counting to 10 do not blow or shake out the small amount remaining in the tip as the pipet is calibrated to deliver a specified volume with a small amount remaining to review the steps are first inspect the pipet for cleanliness and rinse the pipet with the liquid to be pipetted use a pipet bulb to fill the pipet above the graduation Mark wipe the outside of the pipat using a lintree tissue to avoid contamination drain the liquid until the bottom of the meniscus sits on the graduation Mark and lastly drain the sample into a receiving vessel retaining the tip of the pipe pet on the wall of the receiving vessel for 5 seconds [Music]