Great description of xylenes, thank you.
While the use of "less than stellar" xylenes may not make much of a difference
in processing tissues, it may when used during dewaxing and clearing of
sections.
Many moons ago we received batches of xylene with a high sulfur content (could
smell this) and this did affect the staining. It was especially noticeable with
metallic impregnations.
While all xylenes will tend to fade metallic impregnations over time, these
batches caused a patchiness that was not apparent with more purified samples of
xylene.
Barry

PMarcum wrote:

> Louise,
> Generally speaking the cheaper the xylenes the more contaminate you will
> have in the final product.  Xylenes are a petroleum distillate by-product
> and are not really very pure.  The purest form you can get is Xylene as in
> 99-100% pure.  We do not use this as rule as it is very expensive in the
> pure form and we, in the laboratory have not been educated enough about
> which reagents are the purest.  We are usually told to buy the cheapest and
> we do not fully look at the possible issues of safety.  Several lectures at
> different NSH meetings have had the information included, unfortunately not
> every one can attend and get the most up to date safety information.
>
> Look at your bottles and ask your supplier for information.  Many years ago
> this came to my attention for a different reason.  I did neuroanatomy and we
> were getting strange areas dry looking material in rat and monkey brain from
> contaminants.  When I checked my XYLENES (always look for the "s") I found
> it had 5-10% unknown contaminates and my supplier did not know what they
> were.  As less than 1% each they do not need to report them and did not care
> to find out what they were.  When this problem occurred they could have more
> than 1% and not report it.  We switched to a different clearing method and
> the problem disappeared.  A pure clearant is your best bet for better
> tissues also.  It is one of the reasons some laboratories with stills are
> unhappy at first.  The still actually removes the contaminants and cleans up
> the clearant or alcohol.  Often these laboratories need to change processing
> protocol as a pure reagent works better and faster.  Pam Marcum
>
> -----Original Message-----
> From: LOUISE YARROW [mailto:LYARROW@HOME.COM]
> Sent: Tuesday, May 15, 2001 11:03 PM
> To: Histonet@pathology.swmed.edu
> Subject: Xylol.or Xylene..Benzene derivatives
>
> Hi,
> Today someone brought to my attention many places are using xylene without
> benzene derivatives.
> Could someone please enlighten me to the quality, and any difference in
> cost.
> Also how many use Xylene or Xylol in 4 litre containers.
>
> Thanks once again  for your replys.
>
> Louise Yarrow
> Foothills Hospital
> Calgary, Alberta, Canada