Re: Help with a "careful with chemicals list"

From: Barry Singer <bsinger@sasktel.net>
Subject: Help with a "careful with chemicals list"
Date: Mon, 13 Sep 2004 19:44:52 -0600

> Does any one else think it might be nice if the chemists on the list
> made a chart of the chemicals we use with reminders of what to watch
> out for?

Those are found in geleral laboratories guides... if you have more
specific questions I'll see if I can help here.

Glass is probably not the best material for storing highly alkaline
solution like your sodium hydroxide solution. HDPE plastic bottles
(the recycle mark has number 2 in it) is probably your best option.
HDPE has pretty good chemical resistance against strong bases and
acids. One weakness of HDPE is its high gas permeability. Sensitive
solutions, such as developer solutions for silver gelatin process
lasts longer in glass or PET (PETE, recycle code 1) bottles.

Another thing to watch out for is temperature limit and reactions that
generates heat. Did you mix NaOH and water in the bottle and left it
in your shelf? Dissolving NaOH in water gives off a lot of heat and
makes the solution hot. PET bottles can sustain only up to 60C or so,
and I suspect the heat killed the bottle, not the NaOH itself. HDPE
can take up to 120C and its safe with boiling water and dishwasher.

Here are two extra pieces of useless information. Soda bottles use PET
because the drink is highly pressurized and it shouldn't go flat by
the time people drink them. If it were plain HDPE or something, drink
could go flat. But PET is a rather difficult plastic to recycle
because of its low thermal durability.

--
Ryuji Suzuki
"You have to realize that junk is not the problem in and of itself.
Junk is the symptom, not the problem."
(Bob Dylan 1971; source: No Direction Home by Robert Shelton)