Cryptic Science

This post is all about the science we used during at the ‘Why Scotland Why East Kilbride performance’: what we did, and why. You have two options: either watch the video blog here (it’s about 5 minutes long and was shot quickly during a break in rehearsals), or read the rest of this post. There are several other posts on this blog detailing the ‘vaporisation experiment’ (see the related articles section below).

(Just a wee note about the video: it was unscripted and so some of the explanations are not as good as I would have liked…)

For the show we’ve put together three experiments: a vaporisation, an extraction and a titration.

Ethyl acetate – Photo: Wikipedia

The vaporisation experiment uses a petri dish, heated to 50-60˚C on a hotplate, to evaporate two solvents while a fan disperses the vapour around the auditorium. The two solvents are acetic acid (the main component of vinegar) and ethyl acetate (an ester found in low levels in wine, but also found in a more concentrated form in products like nail polish remover). In rehearsal tests it’s been quite effective, even at the low levels we’re using to ensure it’s all well within safety margins. Together with the CCA staff we’ve spent quite a while over the last couple of days formalising the safety and risk assessments. (See ‘This lab smells…”)

The extraction experiment simulates a technique where one compound is separated from others by using differences in how readily chemicals dissolve in two, non-mixing, solvents: usually one based on water and the other a ‘hydrophobic’ (literally water-hating) organic solvent. Here we have replaced the organic solvent with olive oil (which is technically still an organic solvent but is safer to handle outside the lab). This sort of ‘liquid-liquid extraction’ is still used in synthesis labs, but in analytical labs it has been largely replaced by techniques like High Performance Liquid Chromatography that can accurately measure lots of compounds in a single sample at the same time.

At the end of the extraction step is we ‘mouth pipette’ a sample. This was common practise in the 1960 and 70’s, and is still is developing countries where resources are scarce, but It’s extremely dangerous because the liquid you’re sucking up can get into the mouth: this sort of accident was treated as an ‘occupational hazard’. In fact the central character of Why Scotland Why East Kilbride, Teddy Edwards, once got a mouthful of ammonia solution this way. There is a great online article about month pipetting in biological labs here.

The titration experiment, with the tall, thin burette and fatter, bulbed pipettes, will be recognisable to most folks who have done high school chemistry .The principle of titration is simple: you measure the quantity of one compound by the way it reacts with another and use some sort of ‘indicator system’ to show when the reaction is completed. Although this sort of analysis may have started in the late 18th century, the main principles are still in use – my lab has an automated Karl Fischer ‘titrator’ for testing the amount of water in samples. For Why Scotland Why East Kilbride we have weak (1M) acetic acid in the burette (which we have slightly coloured with pH indicator) and a 5% sodium bicarbonate solution in the glass dish (normally this would be a conical flask but we get a better sound effect from a thicker glass dish). The sound during the performance is the ‘ting’ of the magnetic stirring bar hitting the glass as it rotates: changing the position of the dish conveniently alters the sound.

The science we have tried to replicate in Why Scotland Why East Kilbride is 40 years old! The equipment we used for the performance has been borrowed from one of our training labs at the University of Strathclyde since we have very little equipment of this ‘vintage’. We have some short video clips of our modern lab at the Cancer Research UK Formulation Unit which shows our biological testing, chemical testing, some of the complex results modern equipment generates and how we handle some of the potent drugs we work with.

If you were at the performance, we how you enjoyed it, and I hope this blog post ‘unpacks’ a bit of the technical stuff for you.

Related articles in this blog

• Art, Science and Safety (drsjford.wordpress.com)
• Cabbage patch thiol (drsjford.wordpress.com)
• Action and Reaction: Art, Science and Safety II (drsjford.wordpress.com)
• This lab smells…. (drsjford.wordpress.com)