homeslice (Stranger)
04-01-03 19:23
No 423059
      Dessicator questions  Bookmark   

Some very simple desiccator questions:
What the fuck is it? smile
How does it work?
Would you recommend it if one had to dry out like a couple hundred grams of p-benzo from the hydro method and if so, what would you recommend?
Is there an advantage to having a vacuum one or a glass one?
And i'm seeing them range in price from 9.99 to 1560.00, ummmm why?

PS I UTFSE and i really had a hard time finding basic information on this thing, just alot of info about ppl substituting shit in for it for drying.

Thanks
 
 
 
 
    VinnyC
(One Man Show)
04-01-03 21:48
No 423095
      A dessicator cabinet is used to dry (strip...  Bookmark   

A dessicator cabinet is used to dry (strip solvents). Vacuum comes in very handy, but you want a cold trap (acetone/dry ice). Also, placing a bed of KOH in the bottom of the cabinet is a good idea.

Cheers...

"This is bat country..." Fear & Loathing
 
 
 
 
    Rhodium
(Chief Bee)
04-02-03 00:06
No 423129
      How a desiccator works  Bookmark   

You place things in a desiccator to dry them (or to keep them dry). It is in effect an air-tight and chemical resistant container which has two compartments, one at the bottom which holds the drying agent (or desiccant) and above this a shelf where you can put beakers or small trays with the solids you want to dry. It is most often made of thick, vacuum-safe glass so that it can be evacuated without any risk of implosion.

The idea is to keep a substance away from any moist air and close to a drying agent (but not in contact with it!), another substance which absorbs water much more strongly than the compound you wish to dry (left overnight, most traces of water will travel from your compound and become absorbed by the desiccant). Concentrated sulfuric acid, sodium or potassium hydroxide pellets or flakes, phosphorous pentoxide or anhydrous calcium chloride all make good drying agents for most substances. Always use an acidic drying agent for acidic substances and a basic one for bases, otherwise salts may form between their vapors.

If you evacuate the desiccator, the process is more rapid, as water vapor evaporates from your moist compound much faster under vacuum, as it is only when it is in form of vapor it will be absorbed by the desiccant. Vacuum is optional though, if your compound does not bind water very strongly. In rare cases it may even be necessary to heat the desiccator to 100C under vacuum to driuve all the water out, but that is most often only necessary for analytical work.