From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Bottom Falls Out of Sulfuric Acid Bottle
Date: Fri, 20 Mar 1998 09:44:31 GMT
Rob Buckley <R.Buckley@sct.gu.edu.au> wrote:
>Eric Lucas wrote:
>> Rob Buckley wrote:
>> > Here in Australia, at least, conc. HCl is sold in plastic
>> > bottles. AS other acids are in glass,
>> This newsgroup is just full of misinformation. Repeat after
>> me--borosilicate glass is *inert* to HCl. And yes, HCl is sold in glass
>> by chemical suppliers here in the US.
>Touchy, aren't we? I was not _saying_ glass is attacked by HCl, but
>simply pointing out that I had never seen conc HCl in glass bottles, and
>had previously assumed (wrongly) that that was the reason.
Ultra-pure acids are usually sold in preleached teflon or
polyethylene containers rather than glass, because glass *is*
attacked by acids. Not many chemical suppliers use borosilicate
glass ( Pyrex ) as their retail chemical reagent containers down
here due to the extra cost, and the glasses used for acid
containers are usually less acid-resistant. Just check the
J.T.Baker catalogue for HCl for trace element analysis.
Most analytical chemists would know that concentrated acids
will leach constituent elements from glass containers over
time, and blanks are used to compensate for the leaching.
The rate of attack is slow ( 100mg/m2 for Pyrex borosilicate
glass subjected to constant boiling HCl for 6 hours, compared
to 190 mg/m2 for 15psi steam at 120C ). The metallic impurities
often do not interfere with the ultimate use of the
acid, so either glass or plastic containers are used for
lower grades of acids, including analytical, general purpose,
and technical. Many suppliers of laboratory reagents
offer both glass or plastic containers, depending on the
concentration and acid.
Even borosilicate glass is not inert, and is not claimed
to be inert by the manufacturers, but the corrosion rate
is usually so low at ambient temperatures that it can
be ignored for most purposes - but even old glass water
stills can corrode away just from exposure to steam, and
the weight loss is noticable - our glassblower has
said that the steam section of our water still body is
now so thin that it will have to be replaced soon.