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Previous by Date: Subject: Re: [DCHAS-L] Pressurization of 5 gallon glass carboy Date: Thursday, February 24, 2022 at 3:09:27 PM Author: Heinz Trebitz <heinztrebitz**At_Symbol_Here**GMAIL.COM> |
Next by Date: Subject: [DCHAS-L] Chemical Safety headlines (17 articles) Date: Fri, 25 Feb 2022 06:22:52 -0500 Author: Ralph Stuart |
A dissenting voice if I may:
If the apparatus involved was inherited in a PChem lab, as described, it
sounds to me like the carboy [or carboys] was probably used for the
Clement-De´sormes Experiment for determining the Ratio of the heat
capacities of gases. I always thought that this had to be one of the most
ingenious experiments in the history of science?so simple, yet yielding
thermodynamic data. I don1t remember the exact specs, but I1ll bet that1s
what the carboy was for. With a bit of luck you might find a manometer in
the lab filled not with Hg, but with an organic liquid, maybe dioctyl
phthalate or some such. I suspect the carboy [or perhaps in a drawer in
the lab] was equipped with a large rubber stopper and three short glass
tubes though the stopper.
Anyway, safety wise: I can1t remember the specs here either, but I would
guess that one pressurizes the gas in the carboy to maybe 10cm of the
low-vp organic liquid, then waits for thermal equilibrium. Once there,
the manometer is read, and the small rubber stopper at the neck is quickly
removed and replaced. That causes an adiabatic expansion of the gas,
which cools it. Then one waits again for heat to flow through the walls,
and reads the manometer a final time. The pressures now reflect an
isothermal expansion interval.
The pressure is increased by using a small hand bulb with a check
valve?not much pressure at all, plus you have pressure relief from the
rubber stoppers and vinyl or rubber tubing. For the Clement-De´sormes
experiment, it is convenient to keep a separate carboy for each gas
studied, which could account for more than one carboy1s having been found.
I1ve had students do this experiment many times [having always been in
very low-budget situations] and don1t wee a problem.
Of course if that1s not what these were for, it1s a new ball game.
If those were used for the ignition of an organic vapor a la Hubert Alyea
et al., if done the carboys should be thoroughly taped and secured behind
appropriate shields. Polycarbonate carboys have been used for that one,
which I never dared to do.
Good luck,
Steve
--
Stephen J. Stepenuck, Ph.D.
Emeritus professor of chemistry
Keene State College
Keene NH 03435-2001
sstepenuck**At_Symbol_Here**ne.rr.com
603.352.7540
Ralph wrote:
>One of our faculty member was doing due diligence inspections on
>inherited equipment he uses in the physical chemistry lab for gas
>demonstrations. He found some defects in glass 5 gallon carboys, so
>ordered replacements. They arrived from DWK-Kimble with precautions
>etched on the outside, including 3Do not evacuate or pressurize unless
>recommended in the current DWK Kimble catalog.2 Unfortunately, the
>catalog does not contain any information about pressurizing or evacuating
>the carboys. It simply says that the carboys are "Ideal for storage and
>dispensing of solutions.2
>
>There are no discernible design differences between the new carboys and
>the older ones. I wonder if anyone on the list has experience with
>assessing the risk associated with gas pressure differences with this
>equipment?
>
>Thanks for any information on this.
>
>- Ralph
>
>
>Ralph Stuart, CIH, CCHO
>Environmental Safety Manager
>Keene State College
>603 358-2859
>
>ralph.stuart**At_Symbol_Here**keene.edu
>
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