In regards to the original question ab out using dichloromethane as an extraction solvent – the sad reality is t hat the alternative solvents don’t work as well as does dichloromethane f or this experiment. A few weeks ago, we performed the extraction of caffeine f rom tea using diethyl ether – the results were very disappointing. Ethyl acetate and 2-propanol have also been proposed for this experiment – both of these are water-soluble. Pedagogical reasons prevent me from using water-soluble solvents for this experiment. Students find the concept of solvent-solvent extraction sufficiently confusing before we make it more complex by using even moderately water-soluble solvents as the ‘water insoluble phase’.

This discussion reminds me of why ther e often is an adversarial relationship between faculty and EHS staff.

Dr. John Nail

Professor of Chemistry

While I agree (mainly) in principle with Ernest, there are some things that really should come off of the list.  An obvious example (and I’m being extreme here, not intending to imply Ernest wouldn’t agree) is benzene.  I’m sure we’d all agree that this is a solvent that simply shou ld not be used under any circumstances.

But ErnestR 17;s point is spot-on.  If a ll we do is ‘dumb down’ the content of labs and remove all possible h int of danger, we exacerbate the problem of a society full of chemophobic individuals who simply do not know how to handle any chemical, much less make a rational decision as to whe ther a given situation is really a problem or not.  Heck, if this is going to be our response (i.e. let’s remove all danger from the lab), we might as well discontinue ‘real’ labs and just do the whole thing as an online & virtual experience.  Take a video of the experiment and l et the kiddies watch it.

I think we do our students (and, ultimately, society itself) a disservice when we immediately presume that we must be the nanny-protector from all harm.  The real w orld does not operate this way (ambulance-chasing, TV ad-trolling trial lawyers notwithstanding).  Far better to teach them what the real issues are a nd how to think critically through a situation to assess it, and to actually perform, hands-on, real chemical reactions with real chemicals and reagents – some of which can harm them – to demonstrate that, with prope r handling, care and understanding, chemicals can and do perform wonderful th ings for us.

I’ll get off my soapbox now.

Brad

Dr. Bradley K. Norwood

Laboratory Dir ector

Arista Laborat ories