Date: Sun, 10 Oct 2010 00:14:59 -0400
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Paul Harrison <pharriso**At_Symbol_Here**UNIVMAIL.CIS.MCMASTER.CA>
Subject: Re: Science Education & Safety
Comments: To: DAVID KATZ
In-Reply-To: <BLU104-DS1444E53B3C3E2C8B13E97C5510**At_Symbol_Here**phx.gbl>


Colleagues: I have an undergrad. lab experiment that uses dichloromethane to extract caffeine, but hadn't thought of changing the solvent. This interesting discussion raises the question of whether there is a "safety series" of solvents, much like the elutropic series. What exactly is the problem with DCM? Is it safer or more environmentally friendly (not necessarily the same thing) to replace 1 mL of one solvent with xx mL of another? What about volatility? Should David replace the hexane in his fries experiment with e.g. heptane, as we have done in the research lab? Does price enter into the "value" of a solvent? On another note, I have recently been involved in assessing chemicals around a pregnant student. I googled "teratogen" and found many sites that quoted ethanol and dilantin and a few other prominent examples. Does anyone know if there is a more complete list? Lastly, I was surprised to find dilantin on the list, especially since we have another experiment in this class in which students make dilantin which has run for years uneventfully (ignorance is bliss). Does anyone know what level of exposure to dilantin is required to exert an effect? Should I worry about the (remote but not inconceivable) possibility that a student in this class is pregnant? My feeling is that the chances of successful synthesis X pregnancy likelihood X likelihood of actually absorbing an adequate dose is pretty remote, when compared to e.g. alcohol exposure for students. I can certainly warn students, but do not want mass hysteria. I would appreciate any expertise. I look forward to continuing to read the excellent posts to this list: keep up the great work! Best wishes, Paul On Sat, 9 Oct 2010 07:41:52 -0700 DAVID KATZ wrote: > I did a quick and dirty web search for a caffeine extraction that does not use dichloromethane. I found this It is by John Thomson at Lane Community College, Eugene, Oregon > > I have not tried this procedure and I would be curious to know how well it works. > > I do not know the scale at which the class at your university performs this experiment, macroscale, small scale, semi-micro, or micro. That will also affect the extraction solvent used. For semi-micro scale or microscale procedures, I agree with Ernie Lippert that students must learn how to work with chemicals such as dichloromethane safely. That includes the generation of only small quantities of waste product. > > In another experiment, I have my class extracting the fat from potato chips and French fries. Starting with 5 g of chips or 10 g of French fries in a 125-mL flask, I have switched the solvent from dichloromethane to hexane and use several rinsings of 10 mL or less. The solvent is disposed of in a waste bottle and the chips or fries which are only slightly damp with solvent, in the flask, are dried in a water bath under the hood. The fat content is determined by the loss in mass. We get good results. > > David > > _________________________________________________________________________ > > David A. Katz > Chemist, Educator, Expert Demonstrator, Science Communicator, and Consultant > Programs and workshops for teachers, schools, museums, and the public > 133 N. Desert Stream Dr. * Tucson, AZ 85745-2277 * USA > voice/fax: (520) 624-2207 * email: dakatz45**At_Symbol_Here** > Visit my web site: > _________________________________________________________________________ Paul Harrison Associate Professor of Chemistry Department of Chemistry and Chemical Biology McMaster University 1280 Main St. W., Hamilton, ON, L8S 4M1, Canada Phone: (905)525-9140 ext. 27290; FAX: (905)522-2509

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