Wolfram
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Material search
Im looking for the following materials:
1. A material that forms komplexes with ethanol and prevents it from boiling away.
Does anything like this even exist?
2. A liquid that is colored in a bright color but becomes colorless after som time in air.. oxidised.
Now a question would normal labglas inplode if the pressure inside was lowered to 1/4 of normal atmospheric pressure?
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Theoretic
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Lab glassware certainly wouldn't implode even under vacuum, lightbulbs have walls about five times thinner and don't implode, even if you
stand on them!
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Saerynide
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Lightbulbs?! REAlly? 
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vulture
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Labglass under reduced pressure should ALWAYS be protected by a net or blast shield. The implosion danger is very real!
Lightbulbs are not under reduced pressured, they're either filled with N2 or Ar. Otherwise they'd give quite a bang when you drop them.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Blind Angel
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Neon glassbulb (the long one) are under vacuum i think, when you break them they bang
/}/_//|//) /-\\/|//¬/=/_
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guaguanco
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| Quote: | Originally posted by Wolfram
Im looking for the following materials:
1. A material that forms komplexes with ethanol and prevents it from boiling away.
Does anything like this even exist?
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Under what conditions? What are you trying to do?
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Theoretic
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Old lightbulbs are filled with vacuum ( ), while newer ones are filled with
inert gas. The great strength of lightbulbs is due to their dome-like shape, while lab glassware has weak spots (such as the middle of the side wall
in conical flasks) since it isn't designed for negative pressure. Lightbulbs with gas filling are likely to have thinner walls, now that they
don't have to withstand negative pressure.
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unionised
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Neon bulbs have neon in them (granted, under reduced pressure) hence the name.
Lab glassware may stand a vacuum but I would be very careful. Large conical flasks (unless rather thick walled) will not.
Titanous chloride solution is violet but oxidises to colorless Ti(IV) compounds.
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vulture
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Slightly basic phenolphtalein solution will turn colorless on air eventually because of CO2 absorption.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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overseer
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Glass under vacuum
| Quote: | Originally posted by Wolfram
Now a question would normal labglas inplode if the pressure inside was lowered to 1/4 of normal atmospheric pressure? |
The ability of glass to withstand pressure differences depend heavily on its shape. Dome-like shapes can withstand higher pressures for the same
thickness, owing to the fact that the external pressure cannot "crush" them easily (remember the simple experiment of attempting to crush an
egg in Your hand): inner parts of the dome material are compressed and solid materials aren't easily compressible. However, flat surfaces, such
as windows, can easily be broken: pressure *stretches* them on one side, and this is where the material fails. So, comparing dome-like light bulbs
with cylindrical tubes is not entirely correct.
Generally, I do agree that implosion is a real danger, so one should always use thick glass. Even then, a protective screen is recommended (e.g. 3 mm
- thick transparent plastic sheets) since invisible micro-cracks in thick glass, or internal thermic stress caused by uneven heating, can cause the
material to fail. I once witnessed such a mishap, so be careful. On several occasions, I witnessed the implosions of standard distillation flasks when
the operators left them to cool and forgot to remove the stopper. It happened when the setup involved bubbling the vapor from the distillation flask
through a liquid in the second flask. In the process, the distillation flask is filled with vapor of the liquid to be distilled, and when it is left
to cool, the temp. reaches back the condensation temp. of the liquid and the vapor condenses. The momentary pressure drop caused the implosions.
Normal incandescent light bulbs are filled with chemically inert gases at atmospheric pressure. Neons are filled at reduced pressure, but not vacuum:
an electric arc (spark) is very thin at atmos. pressure, but with reducing pressure, the arc widens. Thus, at reduced pressure, an electric discharge
arc fills almost the whole volume of the neon tube. Besides, the spark is obtained with lower voltages, so You can ignite a long neon tube with a 7 kV
neon transformer, while You'd need ~30 kV per centimeter for a spark in dry air at 1 atm.
If You want to get an idea about how thick a glass is considered "safe" for vacuum applications, You can try to locate and inspect a piece
of a shattered TV or computer monitor CRT (cathode-ray tube, i.e. monitor screen). These tubes are evacuated in order to prevent collisions between
gas atoms and accelerating electrons.
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