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I would like to evacuate a vessel (a glass round-bottomed flask) and which contains a few grams of platinum. However, I am worried about the platinum powder being sucked up by the vacuum.

A few people told me that this is possible if I take some care, but I am still not convinced. I use a turbo pump in combination with a diaphragm pump for the rough vacuum. So in the end a very expensive vacuum cleaner! I know that the powder will destroy the turbo pump if the powder is sucked in. Do any of you have some experience with powders in vacuum?

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  • $\begingroup$ Two questions: In what order do you intend to connect and switch on the pumps? And what is the reason a vacuum cleaner works? Hint: There is no vacuum involved. $\endgroup$ – Karl Jul 26 '18 at 19:13
  • $\begingroup$ Why are you using a turbopump? I would imagine that the off-gassing of ground glass oil would be continuous. Is there a need for ultra high vacuum. $\endgroup$ – A.K. Jul 26 '18 at 22:58
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I often high-vac powders on Schlenk. Issues only arise when going between positive and negative pressures though to minimise any risk I often lightly plug the sidearm of the glass stopper/adapter(?) with cotton wool. Glass wool would also suffice and I am certain there are already stoppers/adapters which have a porous mesh build in to prevent powder from entering the vacuum system.

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It is standard procedure for air-sensitive chemistry to apply a vacuum to a flask containing a solid. Most of the equipment used routinely for this involves a vacuum/gas line that allows the connection of the flask either to a source of an inert gas (nitrogen or argon) or a vacuum using a switchable stopcock (so you can evacuate all the gas and then fill the vessel with something inert). Nobody connects a vessel directly to a vacuum pump and the gas vacuum line is shielded from the pump with traps (usually cooled to liquid nitrogen temperatures) to collect any material entering the line (both solids and volatiles) that you don't want to get into your pump.

Using such an apparatus requires a certain amount of skill. One such skill is not applying a vacuum too quickly (which might cause some material in the flask to be blown into the line). Careful and slow application of the vacuum will avoid this and careful observation of the flask while applying the vacuum will help you learn just how fast you can afford to apply the vacuum. But it might be worth learning this with a cheap powder before you try it with platinum.

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