Sciencemadness Discussion Board

Alternative to dessicators

Amos - 8-9-2014 at 18:11

I've seen a lot of procedures on sciencemadness that describe using a dessicator to quickly dry compounds produced through wet processes, even if the compounds aren't all that hygroscopic to begin with. Since before I even started home chemistry, I possessed a food dehydrator, similar to this one right here:
http://www.amazon.com/Nesco-FD-37A-American-Dehydrator-400-w...

In addition to being great for drying herbs and botanicals so that you can use them for chemistry, and for making excellent dried foods, my food dehydrator, which I got for around $30-40, very quickly dries my chemicals without me having to worry about preparing/recycling a dessicant all the time. It has even completely dried sodium hydroxide when I needed it to.
So here's just an alternative idea to using a dessicator; not sure how much money you could save, but certainly it could save some time.

Texium - 8-9-2014 at 19:08

Wow, nice. I just use a big jar with a bunch of calcium chloride in it. Nothing too fancy, and it still keeps for a long time before liquefying.
How long did it take you to dry your NaOH with that?

Dr.Bob - 8-9-2014 at 19:34

The food drier is somewhat like the electronic desiccators that a few companies sell, which simply dry a silica gel cartridge and then use it to keep the inside dry. But the price is a lot better. For a cheap desiccator, it seems like a reasonable device. Just be careful that you don't dry anything with flammable vapors left in it, as I doubt that it is safe for that, I much prefer drying things with a high vacuum pump, that generally works faster, but is not practical for most home labs. But it is faster in most cases. I would not use the same food drier for chemicals and food.

Amos - 8-9-2014 at 20:14

Bob, the dryer trays are easily dishwashed, which I'd say is a pretty safe bet when you put the food on top of paper towels, etc. Generally even the wettest of chemicals only need 1-2 hours if you fluff it up to give it some surface area. NaOH was no exception.

Varmint - 9-9-2014 at 03:57

My main objection to a food dehydrator is the open nature of the incoming air.

They operate by providing gentle heat coupled with low to moderated airflow.

As operation continues, "fresh" air is continuously drawn through the unit, including dust, organic aerosols, pollen, and basically anything else one might expect to find airborne.

In other words, while it may have uses for a limited number of chemicals, you might just want to use more traditional methods when working with things you expect to retain bonafide purity, and use extreme caution when processing oxidizers.

I wouldn't even remotely consider it for drying chlorates, and encourage you to avoid the temptation as well.

DAS

Praxichys - 9-9-2014 at 04:38

So:

No oxidizers
No flammable solvents
No solvents whose vapors attack the plastic (DCM/TCM?)
Risk of contamination by dust
Compound must not melt, degrade, or sublime at 70C for extended periods
No solvent recovery, solvent ejected into room

Sounds good for maybe inorganic wet chemistry. Personally I'll stick with the vacuum desiccator. The price was about the same!

Dr.Bob - 9-9-2014 at 05:21

I just put my compound into a rb flask or vial and then attach that to the vacuum line via a gas inlet tube or for vials, I often put them in a lyopholyzer jar (freeze drying jar), with a rubber lid, they are great for holding vials of powders. I normally put a kimwipe over the vial opening and rubber band it into place to help prevent the powder from leaking out or any other materials from getting into the vial. You don't want to overfill any of those, I like to only have a small amount of material in a flask or vial (10-20% of the space filled) as that helps it dry better. The vacuum will pull off water, solvent and even some reagents that are volatile.

Amos - 9-9-2014 at 05:57

Yes, obviously a dessicator and this device are two different things. I just made the post because I have seen time and time again people using a dessicator for insoluble inorganics and such because they don't want to wait for it to air-dry. I suppose it's really more of a beginner's tool. And I hadn't heard of vacuum desiccators before; those sound a lot more promising than this, but again, for those that can't afford a proper vacuum pump, which is a lot of us, those aren't as feasible.

[Edited on 9-9-2014 by No Tears Only Dreams Now]

careysub - 9-9-2014 at 06:07

Quote: Originally posted by Varmint  
My main objection to a food dehydrator is the open nature of the incoming air.

They operate by providing gentle heat coupled with low to moderated airflow.

As operation continues, "fresh" air is continuously drawn through the unit, including dust, organic aerosols, pollen, and basically anything else one might expect to find airborne....


This problem is easily addressed. Run it with a box inverted over it that has a section of FRP-10 (ideally) furnace filter installed on one or more sides. With the miracle of duck tape you can make the box entirely out of 5 furnace filters!