Hello, I am about to buy a glass vacuum desiccator for cold mercury development.

[Dafna Gazit]

Hello,

I am about to buy a glass vacuum desiccator for cold mercury development.

The seller in the chemists’ equipment shop advised me to by the German product instead of the chines one which is a lot cheaper than the German desiccator.

He claimed that the chines desiccator won’t hold for 24 hours in a vacuum because of the finishing of the glass.

I can only afford the chines glass vacuum desiccator.

Does anyone have an experiens whith a chineese desiccator?

thanks

Dafna

[photolytic]

Dafna,

I’m not familiar with the Chinese glass dessicator but my main concerns would be the thickness of the glass and the type of seal. Glass on glass is better than a telfon seal.

A picture would be very helpful.

John

[Dafna Gazit]

I saw a picture of it. it suppose to be somthing like the attached file

 

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[photolytic]

Dafna,

The desiccator in the pic looks as if it has a small Teflon valve at the top. These tend to leak as the Teflon is soft is soft and deforms under pressure. Even if the valve actually has a glass stem, the width of the greased seal is rather narrow and begins to leak after a few turns of the valve. Better to get the “German” or Pyrex design with large rotating glass valve collar valve on top of the lid. These need greasing periodically as they tend to tighten up when the grease film spreads out with use but they leak less than the smaller valves.

http://www.ebay.com/itm/370470077386?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I should explain that all desiccators can leak slightly even through a well greased ring seal. A 24 hour seal is not absolutely mandatory as the Dag development rate depends mainly on the maximum (initial) vacuum and the developing time rarely exceeds 3 hours at 20C.

[Dafna Gazit]

Thank you, Photolytic, that was very helpfull.

you mentioned that there will be leaks anyhow, in that case is it possible during the vacuum developmaent time, to re- vacuum the Desiccator?

[Author]

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