Serial Dilutions « Richmondschoolbiology’s Weblog

These are used a lot in biology and our syllabus requires us to know how to do them. They allow us to dilute a stock solution in small steps rather than in one giant leap. This means that instead of measuring a very small volume of the stock solution (which is prone to errors) we can use larger volumes. This improves the accuracy of the resulting solutions. It is also faster than making up each concentration separately from scratch.

A common dilution is 10x – we take 1ml of the stock solution and add 9 ml of distilled water to dilute by a factor of 10; this is repeated with the newly produced solution in place of the stock to produce a further x10 dilution. If our orignial stock solution was 1M then the dilutions would be 0.1M, 0.01M etc. This is shown in the diagram below:

You can read more about this on the SAPS website and watch a you tube video clip.

NHS Choices: Behind the Headlines

Exercise linked to fertility November 9, 2009

“Gym workouts ‘can hit pregnancy hopes’,” warned the Daily Express today. The newspaper said that Norwegian study has apparently found that “superwoman workouts” triple the likelihood of fertility problems. This study found that high-frequency, high-intensity exercise was associated with a risk of infertility. However, the study cannot prove that heavy exerc […]

Lorenzo's oil disease gene trial November 9, 2009

The genetic brain disease that was portrayed in the film Lorenzo’s Oil “has been stopped in its tracks by a gene therapy”, according to The Times. This rare but fatal disease, called adrenoleukodystrophy (ALD), is caused by a mutation in a gene. Although the disease can be treated by bone marrow transplant, this requires a suitable bone marrow donor to be fo […]

Bad Science

The Nutt Sack Affair (part 493) November 7, 2009

Ben Goldacre, Saturday 7 November 2009, The Guardian Obviously it’s pleasing to see, in the storm of commentary over Professor Nutt’s sacking, that everyone outside of politics now recognises the importance of scientific evidence in devising laws. But a strange reasoning twitch has appeared, in the arguments of politicians and right wing commentators. Scienc […]

Political woo October 30, 2009

Ben Goldacre, Saturday 31 October 2009, The Guardian. Every now and then it’s fun to dip into the world of politics and find out what our lords and masters are saying about science. First we find Brooks Newmark, Conservative MP for Braintree, introducing a bill to reduce the age for cervical cancer screening to 20. The [...]

The Naked Scientists

Tripping over Psychoactive Toads October 13, 2009

For anyone fresh out of frogs and tempted to kiss a toad instead, this article has a word of warning. Although certain species of toads do make hallucinogenic chemicals linked to a lively "trip", many produce a lethal cocktail of cardiotoxic compounds that could turn such a trip into a once in a lifetime experience, en-route to the mortuary. So whi […]

Deconstructing Chomsky - Re-writing the Innate Rules of Grammar October 1, 2009

Noam Chomsky, a rookie professor at MIT, published a ground-breaking book called Syntactic Structures, which set out a theory of Generative Grammar. He suggested that a Universal Grammar (UG) of basic linguistic principles and a Transformational Grammar of rules responsible for putting sentences together was hard wired into all of us. Some don't agree i […]

Richmondschoolbiology’s Weblog