interesting phenomena - what causes this corrosion/yellow staining? photos provided

Hey everyone,

Something has happened to my chemical storage cabinet. The cabinet shows a very visible discoloration, and the hinges has sustained heavy surface corrosion. Not shown in the photos, is that the discoloration has also affected other containers of chemicals. A stack of papers that was stored in the same cabinet has also been heavily stained yellow.

The following chemicals was contained within the cabinet. They've been stored here for atleast a year:

-Calcium carbide (tech. grade, not stored in air tight container).
-An airtight bottle of Dichloromethane
-2 small airtight bottles of Iodine crystals
-about 2 pounds of Hexamine, stored in a white PE bottle
-1 pound of sodium nitrite, stored in white PE bottle
- + small quantities of magnesium sulfate, sulfamic acid, sulfur powder, and for some reason, tartaric acid

I suspect the main culprit to be the carbide, as this was stored in a glass jar, and it looked like a large part of this carbide had reacted. I remember when i placed the carbide in the glass jar, it consisted of pieces of clean carbide. When i recently inspected the jar, the carbide pieces was covered by a fine dust/powder. I guess this means the carbide has reacted with moisture in the air, resulting in Ca(OH)₂, and other stuff from the technical grade carbide.

So what do you guys think? What has caused these yellow stains and corrosion?

Thanks for any answers, cheers

Quote: Originally posted by oblivious_terpene

-2 small airtight bottles of Iodine crystals

I'd say if it wasn't for those terribly corroded hinges that you got a pretty fashionable cabinet now
Looks a lot more like iodine damage to me, even stoppered teflon-lipped bottles have caused such rusting for me. If you have some sodium thiosulfate, you could try applying a solution to the stains and see if the discoloration goes away. I can't see how carbide, reacted or not could cause such staining (am I right in assuming only the edgings show a distinct, uniform stain)
Storing the iodine in a two ziplock bags has taken care of the problem for me. Clean up the hinges with SS wool and lacquer them with some thinned polyurethane varnish, or one of those varnishes in a spray can. They should be good for some time.

Eye oh dine!

The thiosulfate trick works like a charm. No need to buy special stuff. Notice the color of the inside of the lid on the secondary container?! Had to do this after my order arrived and my other half wouldn't stop complaining of the "medicine" smell

Just a table spoon of thiosulfate works nicely.

Quote: Originally posted by Mailinmypocket

Eye oh dine! The thiosulfate trick works like a charm. No need to buy special stuff. Notice the color of the inside of the lid on the secondary container?! Had to do this after my order arrived and my other half wouldn't stop complaining of the "medicine" smell Just a table spoon of thiosulfate works nicely.