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