Arochlor

On behalf of Monona Rossol <actsnyc [at] cs__com>
Lisa Goldberg <lgoldberg [at] stny__rr__com> writes

>    I don't know some of you are old enough to be working when
>    Aroclor (PCBs) was still being used. But PCBs are really heating
>    up as a subject with EPA's recent announcements about caulks.  I
>    think it would be a good time to bring up management of historic
>    slides mounted in Arochlor.

I believe the correct spelling is Aroclor.  Walter McCrone of
McCrone Research Institute, Chicago was one of the main promoters of
the use of this material for making microscope slides.  I believe
that there were two different refractive indexes.  It worked just
like Canada balsam but had a  higher refractive index and it was
ideal for making slides of pigments.   When I worked at the Freer in
the 1970s we had a jar of it on the table for use  in making
microscope slides next to our jar of Canada balsam.

Walter McCrone applied for and got an exemption so that we could all
keep using Aroclor for making slides.  It's listed in OSHA's PCB
Regs part 761--I believe this dated June 27, 1988, but the website
wasn't working well enough  that I could confirm this.  Here's the
relevant paragraph:

    Subpart E - Exemptions

    761.80 Manufacturing, processing and distribution in commerce
    exemptions. (a) The Administrator grants the following
    petitioner(s) an exemption for 1 year to process and distribute
    in  commerce PCBs for use as a mounting medium in microscopy:
    (1) McCrone  Accessories Components, Division of Walter C.
    McCrone Associates, Inc., 2820  South Michigan Avenue, Chicago,
    IL. 60616.

It's still listed in one of their forensics courses: see

    <URL:http://www.mcri.org/
        home/section/10-15-312-315/
        nij-advanced-forensic-microscopy:-paint-and-polymer>

    **** Moderator's comments: The above URL has been wrapped for
    email. There should be no newline.

The McCrone catalog now lists a bunch of Cargille Meltmount
materials (actually, I should probably buy one of these) with
various refractive  indexes. It doesn't really say what these
thermoplastic materials are, but  I bet that they don't contain
PCBs.

    **** Moderator's comments: PAN has entries for both spelling
    spellings as "the most common name used for the particular
    chemical."

    Arochlor (composition unspecified, PCBs and/or PCTs)
    <URL:http://www.pesticideinfo.org/
        Detail_Chemical.jsp?Rec_Id=PC36535#ChemID>

    cf

    Aroclor
    <URL:http://www.pesticideinfo.org/
        Detail_Chemical.jsp?Rec_Id=PC35822>

Tom Chase
Chase Art Services
Woodstock,  CT


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                  Conservation DistList Instance 23:17
                 Distributed: Sunday, November 15, 2009
                       Message Id: cdl-23-17-007
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