π§« Laboratory techniques for biologists
Health and Safety
Liquids and Solutions
Separation Techniques
Electrophoresis
Antibody Techniques
Microscopy
Aseptic Technique and Cell Culture
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Lipids and solutions are prepared in the lab as nutrients for growing microorganisms, buffers to hold proteins in their correct folding, chemical solutions to undergo various reactions, and anything else one’s mind can think up. In the lab setting, even plain water needs to be pure, and pH is measured to one decimal point. Liquids can be handled down to each individual tenth of a microlitre, which is a 10,000,000th of a litre.
A common task when handling liquids in an experiment is the need to dilute a stock into multiple serial dilutions with decreasing concentration of the solute in the solvent i.e. glycerol in water. For example, 5 tests are undertaken, each a tenth of the concentration of the original solution. So a 50% glycerol solution of 10 mL (which contains 5 mL of glycerol and 5 mL of pure water) is used to create the subsequent 4 solutions.
In this serial dilution, a tenth (i.e. 1 mL) of the original solution is added to a new tube, and made up to 10 mL with 9 mL of pure water. This is now a 5% glycerol solution. A tenth of this is used to make the next solution of 0.5% glycerol, and so forth. This is a log dilution series because each dilution is a factor (in this case of 10) less concentrated that the previous.

Depending on how dilute we need the solution……