# Pyrex Vacuum Desiccator



## philddreamer (Feb 29, 2012)

I went to the University of Washington surplus store & saw this item. I had no clue what it was... maybe some kind of lab dehydrator!? 
Well, after a search I found it's a vacumm desiccator & from the measurments, I believe is a 3.8L.
Now I hope I can find some good use for it... :mrgreen: 

Take care!

Phil


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## Acid_Bath76 (Feb 29, 2012)

Phil, 

Nice find! Great volume as well.


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## goldsilverpro (Mar 1, 2012)

They are normally used for drying small samples to a constant weight for gravimetric analysis. I used them mainly for things like silver chloride. A small Gooch porcelain crucible, usually made by Coors, (it has small holes in the bottom of it) was placed in a cup-shaped rubber seal on a vacuum filter flask. The crucible was first lined with asbestos fibers (they use something else now) and then the solution containing the precipitate you want to weigh was filtered (and rinsed) through it. The fibers retain the ppt and prevent it from exiting through the holes. I haven't used one since the early 70s. I'm thinking we used a thin layer of lab stopcock grease to seal the lid. You must put some desiccant material under the plate to absorb the moisture. Concentrated sulfuric is a common desiccant. There are also some sort of desiccant stones you can buy from a lab supply. When saturated with water, they turn colors. I think when dry, they are pink and when full of water, they turn blue (it may be the other way around). They can be dried (when dried, they turn back to pink) and reused.

The crucibles containing the samples are occasionally removed and weighed on an analytical balance. If they weigh less than they did the last time you weighed them, they are put back into the desiccator. You do this until the weight is constant.

It looks like there is a side-arm on the top where a vacuum can be pulled. I think this could be used instead of a desiccant.

Gravimetric analysis, in the right hands, can be quite accurate. In the literature, there are gravimetric analysis procedures for analyzing most everything. 

Great find, if the chip on the lid doesn't affect the seal. There have been quite a few times over the years when I wished I had one. I would bet that Lou has used these a jillion times. 4metals also.


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## jimdoc (Mar 1, 2012)

Here is some reading for you;

http://www.archive.org/search.php?query=gravimetric%20analysis

Jim


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## MysticColby (Mar 1, 2012)

I know about these ^_^
They are used for all sorts of things, including vacuum desiccating (They'll hold a vacuum for about 24 hours). I purchased a plastic version to remove air bubbles from silicone before pouring a mold.
I'm not sure how useful it'd be in refining...
I suppose it can be used as an air-tight desiccator container (add some desiccant to the bottom, put wet powder in a cup in the top, wait several days). I've tried to use it as an evaporator, but it doesn't work too well (A vacuum speeds evaporation, but when things evaporate, they lose heat and decrease in temperature, which then decreases the rate of evaporation). It could work as an evaporator if you could somehow then apply heat...


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## philddreamer (Mar 1, 2012)

Thank you gentlemen!

Chris, it still has 5/8th of an inch on the lid & it still seals good.

I'll just need to figure how I'm going to use it ... or just sell it & buy some glassware I could really use. we'll see...

Phil


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## samuel-a (Mar 1, 2012)

philddreamer said:


> Thank you gentlemen!
> 
> Chris, it still has 5/8th of an inch on the lid & it still seals good.
> 
> ...



Seems useful for drying pgm's colored salts.
That would probably be the first thing i would use it for...


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## philddreamer (Mar 1, 2012)

Thanks Samuel! 8)


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## lazersteve (Mar 1, 2012)

I have two large ones in my lab, one has a broken vaccum arm.

I have no real use for them as I do not like to dry out my silver chloride or PGMs salts. I'm a firm believer in converting these salts to the metals shortly after they are produced. 

PGM salts are *much* safer to handle and convert to sponge when wet and silver chloride is much easier to convert to silver when it has not been dreid.

They are really cool items though.

Steve


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