Tuesday, 23 September 2014

Not all solutions or liquids can be pipetted easily!

During the first skills test, some of you were able to answer the question relating to glycerol, but most were not. There was a statement that suggested you try pipetting the glycerol solution at the front of the lab. However, many of you attempted to answer the question "theoretically". I cannot stress the importance of experiments and this is one simple example of why it was necessary to at least attempt to pipette the glycerol.

Like a number of compounds, glycerol is viscous, it is more like motor oil, or a thick shampoo than water and it has a density (see here for a refresher) that is greater than water (which is 1, and is why 1ml of water weighs 1g). It is sometimes necessary to think laterally when preparing solutions and in this case, weighing the liquid is one way of ensuring that an accurate volume of the stock glycerol liquid is added to water to make a final dilution. And it may be necessary to make a larger volume of the solution than you need depending on the availability of precision balances.

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