Rev. 01/10 JEB GLASSWARE CALIBRATION 1. Objectives
Verify the actual volume of liquid delivered by 2 different types of glassware devices. Evaluate which measurement method is better for different uses. 2. Techniques
Buret use: Put the buret in a buret stand and approximately fill it with temperature-equilibrated water. Make sure that the tip of the buret is filled with water and that there are no air bubbles remaining in the buret tip or valve. Record the initial level – it does not need to be exactly “0.00 mL.” Place the bottle under the buret; open the stopcock and allow slightly less than the desired amount to flow into the bottle, and then slowly add the last few drops to bring the meniscus to the line exactly to the desired volume below the initial volume. Touch the tip of the buret to the interior of the plastic bottle to collect the last drop measured from the buret. Record the final level of the buret and calculate the actual amount dispensed by subtracting the two readings, even if you do not dispense exactly the desired amount. Make sure to read the meniscus correctly and estimate the final digit on the reading (0.01 mL). Volumetric pipet use: Squeeze the bulb to empty it. Gently but firmly hold the compressed bulb against the top end of the pipet. It will not stick there on its own, but is held on by your pressure – but it doesn’t need much! Slowly allow the bulb to expand, drawing water up the pipet to just above the line – do not draw water into the bulb. Quickly remove the bulb from the pipet and place your finger or thumb over the top of the pipet to prevent the water from draining out. Slowly release the pressure to bring the meniscus to the line. Remember to read the meniscus correctly! Transfer the contents by releasing water into you bottle; do NOT blow out the contents using the bulb, but rather touch the tip of the pipet to the inside of the bottle to transfer the final remaining drop, but leaving liquid inside the tip. Mettler Balance...
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