The accurate use of pipettes is essential to the success of an experiment. Pasteur pipettes are not graduated at all, therefore, cannot be used for quantitative transfer. Transfer of liquid with a pipette can be best achieved by placing the tip of the pipette slightly below the surface of the liquid to be transferred and drawing liquid up into the pipette until the meniscus is 2 to 3 cm above the graduated mark. Then slowly drain out excess fluid until the meniscus is at the desired graduated mark. Delivery of a specified volume of solution to the receiving vessel is done by holding pipette vertically with the tip of the pipette in contact with the surface of the receiving vessel until the specified volume is released.
Buffers are mixtures of weak acids or bases and their salts.
Choice of buffer depends on the pH range required. Although for most of the experiments in this part of the course buffers will be supplied, students should be familiar with buffer preparation procedures.