John,

Of course, you’re right.  In my comments, I was f ocused on the academic teaching lab, not the academic or industrial research labor atory.  Obviously, there are many reagents, reactions, conditions and procedures th at are undertaken in the research lab that would never be attempted in an undergraduate teaching lab, especially in an introductory level (i.e. Chem. 101 or even organic).

So, yes, with the right training and respect benzene or even diazomethane can be used in the right way at the right time and for the rig ht reasons.  But neither one should show up in a teaching lab.

My main point, though, was that students should be taught pr oper care and respect for chemicals, both in the sense that they do have potenti al for harm, but properly harnessed and handled, they have improved the lives of billions.

Brad

Dr. Bradley K. Norwood

Laboratory Director

Arista Laboratories

1941 Reymet Road

Richmond, VA  23237

(804) 271-5572 ext. 307

(804) 641-4641 (cell)

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I need to take exception with the statement ‘benzene R 30; is a solvent that simply should not be used under any circumstances’. Research involving very reactive organometallic molecules uses hexadeuterat ed benzene (C6D6) as a solvent for NMR samples. The alternatives solvents eith er react with the sample molecule (example: CDCl3) or are prohibitively expens ive (example: D12-cyclohexane).

In regards to the original question about using dichloromethane as an extraction solvent – the sad reality is that the alternative solve nts don’t work as well as does dichloromethane for this experiment. A few weeks ago, we performed the extraction of caffeine from tea using diethyl e ther – the results were very disappointing. Ethyl acetate and 2-propanol h ave also been proposed for this experiment – both of these are water-solu ble. 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 moderat ely water-soluble solvents as the ‘water insoluble phase’.

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

Dr. John Nail

Professor of Chemistry

Oklahoma City University

While I agree (mainly) in principle with Ernest, there are s ome things that really should come off of the list.  An obvious example (a nd 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 should not be used under any circumstances.< /span>

But Ernest’s point is spot-on.  If all we do is ‘dumb down’ the content of labs and remove all possible hint of danger, we exacerbate the problem of a society full of chemophobic individu als who simply do not know how to handle any chemical, much less make a rational decision as to whether a given situation is really a problem or not.  Heck, if this is going to be our response (i.e. let’s remo ve all danger from the lab), we might as well discontinue ‘real’ l abs and just do the whole thing as an online & virtual experience.  Ta ke a video of the experiment and let 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 world does not operate this way (ambulance-chasing , TV ad-trolling trial lawyers notwithstanding).  Far better to teach them what the real issues are and how to think critically through a situation to asse ss 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 proper handling, care and understanding, chemicals c an and do perform wonderful things for us.

I’ll get off my soapbox now.

Brad

Dr. Bradley K. Norwood

Laboratory Director

Arista Laboratories

1941 Reymet Road

Richmond, VA  23237

(804) 271-5572 ext. 307

(804) 641-4641 (cell)

brad.norwood**At_Symbol_Here** aristalabs.com

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