Getting desiccant, oxygen scavenger too?

[AzoMittle]

Hey everyone,

 

I decided to purchase some desiccant to help keep my chems dry and was wondering if there is any reason to purchase an oxygen absorber also? I have never heard of them before now but they keep popping up alongside the desiccant.

 

Also, is there a preferred type of desiccant?

[MrB]

Silica-gel, since it can be regenerated. Preferably by the bucket. The kind that changes color when it does it's thing. (Nowdays i think most do that)

B!

[Milyan720]

Use hand warmer as oxygen absorbers

[Mumbles]

Use hand warmer as oxygen absorbers

 

You really should perhaps try to know what you're talking about before you try giving advice. Iron based oxygen absorbers, such as hand warmers, require water to function. They'll be rendered useless and ineffective by the desiccant.

 

I'm not sure what the requirements of other non-ferrous based materials are. I doubt they're really needed anyway. Only Mg or maybe MgAl would really benefit from them. Probably a few esoteric things people continue to use like copper (I) chloride as well. Water is a bigger issue for most thing.

[AzoMittle]

Sounds good, thank you MrB and Mumbles.

 

Update for those that find this later:

 

I was doing more research on the topic and saw that ferrous oxygen absorbers actually require (and usually provide themselves) some degree of moisture in order to oxidize the the iron powder and therefore scavenge it from the air (as Mumbles has pointed out); counterproductive to the desiccant. Non-ferrous seems to be a mixed bag, I have not seen any that explicitly state 'zero moisture' yet though.

 

It is also noted that ferrous GOX (Gaseous Oxygen) absorbers will heat up (as per Milyan720's suggestion of "Use hand warmer"). I do not know to what degree but this does pose a safety issue.

 

The storage container used is of importance also. Ziploc bags and standard 5-gallon buckets will not provide a sufficient seal to the outside atmosphere. Mylar bags or gamma seal bucket lids seem to be the best choices for pyro. Canning jars could also potentially be used however they pose an additional risk of: chipped glass shards over time, shattering the jar by dropping, shrapnel in the event of an accident, and the nuisance of boiling the rubber lid seal.

 

edit: When using absorbers make sure to check the bag they come in is properly sealed and the indicator is reading a good value, if not return the product. When loading the absorber into your container make sure to vacuum seal any unused product within 10-15 minutes of exposure to atmosphere; if you cannot vacuum seal you should also try to eliminate unnecessary air as much as possible, squeeze out the air and/or add a filler content such as sand, rice, or possibly oil.

 

Finally, it is advised to not use GOX absorbers with powders such as sugar and salt as they will harden to a brick like solid. I am unsure of whether this is due to hygroscopicity or compression by vacuum in relation to atmospheric pressure.

 

edit: See above. Summary: treat unused absorbers like finished composition, put it away securely.

Edited August 26, 2014 by AzoMittle

[Milyan720]

I'm pretty sure that water is more of a catalyst for the hand warmers, but there should be enough water in the air for them to be activated

Toe and feet warmers can reach temperatures of 165 degrees Fahrenheit if left out

Edited August 27, 2014 by Milyan720

[Mumbles]

I'm pretty sure that water is more of a catalyst for the hand warmers, but there should be enough water in the air for them to be activated

Toe and feet warmers can reach temperatures of 165 degrees Fahrenheit if left out

 

 

Nope, actively required for function. Without the water and salt working together, it's going to oxidize the surface of the iron and stop abruptly. This fact means it's not going to work as an oxygen absorber. 65% humidity is generally the figure I was seeing. No closed container, having a desiccant will have anywhere near enough moisture present, and will actively pull the moisture intentionally included in the package itself. It'd be easy enough to try out if you don't believe me.

[Milyan720]

so the oxide layer acts like a passivation layer

Im learning things, thanks mumbles

[MrB]

Im learning things, thanks mumbles

He's real good that way. The variety things i learn reading here is nothing short of astonishing, and a lot of it comes from that source... And he's a pretty good source when it comes to pyro related info as well.

B!

[stix]

Hi there, my first post on this forum.

 

I've been experimenting with small 'sugar motors'. Unfortunately this fuel is very hygroscopic, so I keep the motors in an air-tight plastic container with some Calcium Chloride Crystals (commonly sold as damp-rid) in the laundry section of your hardware store.

 

It loves to suck up moisture - to the point that left out in the open it will turn to liquid after a week or so depending on humidity.

 

Works for me, and very cheap. Cheers.

Edited August 29, 2014 by stix