DCHAS-L Discussion List Archive
Date: Wed, 13 Oct 2010 15:47:22 -0500
Reply-To: chemsafety**At_Symbol_Here**verizon.net
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: "Jay A. Young" <chemsafety**At_Symbol_Here**VERIZON.NET>
Subject: Re: Science Education & Safety
Paul,
You ask " What exactly is the problem with DCM?"
Answer: To learn the hazardous properties of a hazardous chemical, go
to the references. Outstanding authorities include the Documentation
Volume published by the ACGIH, and Patty's Toxicology, a multi volume work
published by Wiley.
Wikipedia and other stuff you can find on the internet--including even
what is reported in the DCHAS e-mails--is not necessarily reli
able.
You may object that Patty sure costs a lot of money, and so does that
ACGIH publication, to say nothing of the time spent in finding and reading
the information aout a chemical in these references.
I reply that the biggest problem in chemical safety today is trying to
get by on the cheap , spending as little money and time as one can get awa
y with--and ending up with ignorance and therefore, vunerability to a
serious "accident" (which could have been prevented if you and others had
spent the required time and money).
Jay Young
>Colleagues:
>
>I have an undergrad. lab experiment tha
t uses dichloromethane to extract caffeine,
>but hadn't thought of c
hanging the solvent. This interesting discussion raises
>the questio
n 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 repla
ce 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 int
o 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 di
lantin and a few other prominent examples. Does anyone know if there
&g
t;is a more complete list?
>
>Lastly, I was surprised to find d
ilantin 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 t
he (remote but
>not inconceivable) possibility that a student in thi
s class is pregnant? My feeling
>is that the chances of successful s
ynthesis X pregnancy likelihood X likelihood
>of actually absorbing
an adequate dose is pretty remote, when compared to e.g. alcohol
>ex
posure for students. I can certainly warn students, but do not want mass hy
steria.
> I would appreciate any expertise.
>
>I look fo
rward 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 <
dakatz4
5**At_Symbol_Here**MSN.COM> wrote:
>> I did a quick and dirty web search for
a caffeine extraction that does
>not use dichloromethane. I found t
his
>class="parsedLink" target="_
blank">https://teach.l
anecc.edu/thompsonj/CH241/laboratory/Caffeine%20Extraction.pdf It is by John Thomson at Lane C
ommunity College, Eugene,
>Oregon
>>
>> I have no
t tried this procedure and I would be curious to know how well
>it w
orks.
>>
>> I do not know the scale at which the class a
t your university performs
>this experiment, macroscale, small scale
, semi-micro, or micro. That will also
>affect the extraction solven
t 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 e
xperiment, 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 hexan
e and use several
>rinsings of 10 mL or less. The solvent is dispose
d of in a waste bottle and the
>chips or fries which are only slight
ly 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 g
et good results.
>>
>> David A. Katz
***************
****************************************
>
>Paul Harrison
&g
t;Associate Professor of Chemistry
>Department of Chemistry and Chemi
cal Biology
>McMaster University
>1280 Main St. W., Hamilton, O
N, L8S 4M1, Canada
>Phone: (905)525-9140 ext. 27290; FAX: (905)522-25
09
>
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