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I'm attempting to do a one-pot synthesis that requires autoclaving the chemical mixture. I thought this process would be greatly simplified by using the lab glass itself as the autoclave in situ without having to transfer the mixture to a traditional autoclave.

Borosilicate lab glassware has a pressure rating of 25 to 30 psi (1.72 to 2.07 bar) at room temperature. A traditional autoclave is set to operate at 15 psi (1.05 bar) and 250 °F (121 °C).

Is it safe to pressurize and heat borosilicate lab glass to these pressures and temperatures in order to use it as an autoclave?

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  • $\begingroup$ Please consult a professional with some experience and provide details about the procedure. Heating any sealed vessel is potentially dangerous and the container must be designed to contain internal pressure. Laboratory glassware is not designed to sustain high internal pressure and open chemicals should not be heated in an enclosed volume . $\endgroup$
    – jimchmst
    Commented Jul 14 at 17:43
  • $\begingroup$ I am doing a specific procedure synthesizing lithium niobate nanoparticles, but this is more of a general question regarding an arbitrary reaction. $\endgroup$
    – Steve Mucci
    Commented Jul 14 at 17:46
  • $\begingroup$ TLDR; Most likely no. Details: A well-made borosilicate glassware usually can survive 1 atm. of underpressure, though risk of implosion remains. Assuming you are warking with water, 250F correspond roughtly 40 atm. of overpressure, which is well above I would consider reasonable for glassware. AFAIK, special glass reactors can operate at 10 atm at most and they are quite costly and unwieldy. $\endgroup$
    – permeakra
    Commented Jul 16 at 3:10
  • $\begingroup$ Every explosive is safe until it explodes. Any missed or hidden scratch or tension on/within the glass may lead to an unexpected event. $\endgroup$
    – Poutnik
    Commented Jul 16 at 12:23

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The temperature and temperature rate of change in an autoclave should definitely not be a problem with borosilicate glass.

However, the pressure might be an issue, (if you mean 15 PSI gauge, that is, ~1 kg/cm2 above atmospheric pressure) which can be accommodated. There is both danger of implosion due to ~1 atm over-pressure, or explosion if the contents of a sealed vessel boil.

  • If you can afford the cost of occasionally destroyed apparatus to save on cost of high-strength labware, autoclave inside doubled or trebled plastic bags, such as these. The wrap might also reduce the chance of small scratches, which greatly weaken glass.
  • Provide some means to equalize pressure inside and outside the container, such as a capillary tube or frit filter in a stopper, or a high-temperature flexible lid (similar, perhaps, to these silicone caps? I could not find "roll-over" sheath closures online.).
  • Use small containers, both because there would be less energy stored in a smaller volume of compressed gas, and because smaller vessels have a higher surface-to-volume ratio. A closed capillary tube might withstand 100 atm, a 1 liter flask, smush.
  • Fill containers almost completely so that a small bubble acts as a stiff spring -- but leave some air space, lest the slightest expansion of liquid shatter the glass.
  • Use solvents with low vapor pressure at 250°F (96.9° Réaumur, 121°C). What solvent is being used?
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  • $\begingroup$ The danger is explosion not implosion [if sealed tubes are involved] open vessels will simply be a mess like putting a filled container in the microwave. $\endgroup$
    – jimchmst
    Commented Jul 14 at 22:56
  • $\begingroup$ @jimchmst, actually, could be either -- implosion due to pressurized autoclave, 15 psi (~1 atm), explosion due to boiling point, depending on contents. $\endgroup$
    – DrMoishe Pippik
    Commented Jul 15 at 1:58
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    $\begingroup$ Réaumur? Should I be impressed you know it, or worry that anybody uses it? $\endgroup$
    – Mithoron
    Commented Jul 15 at 12:07
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    $\begingroup$ @Mithoron, use of Réaumur was no stranger than OP use of "Fahrenheit" -- actually, an attempt at humour to point out that usage. Perhaps one measure velocity in furlongs/fortnight, and atomic radisu in femto-li... $\endgroup$
    – DrMoishe Pippik
    Commented Jul 15 at 13:15
  • $\begingroup$ Dr Moishe: Autoclaves usually run at atmosphere aka 15psi Sealed tube reactions with headspace are pressurized by thermal pressure increase and increased vapor pressure there is no boiling. Boiling is a result of the vapor pressure pushing back the atmosphere [Enthalpy vs energy]. Without headspace liquid expansion shatters glass or plastic containers and hopefully only expands metal altho bombs do shatter. Unless the tube is sealed with vacuum air P inside will be the same as outside Pressure will have no effect on reaction so increased pressure is foolhardy except to stop explosion. $\endgroup$
    – jimchmst
    Commented Jul 15 at 22:15

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