Chemistry Forum

My 90 year old mother in law thinks that she nearly killed her kids 70 years ago because she washed an aluminum cooking pan with bleach and later that day all her kids that ate the food from that bleach cleaned pan got sick. I have not found a single item online to show that other then oxidizing aluminum and discoloring it that there could be any health concerns. I tried to figure a reduction of NaOCl and Al or Al₂O₃ HELP ME reassure that while she might have sickens them with bad food she did not make them sick from chlorine and aluminum!

Thanks in advance!

danadeb, let your 90yr old mother to live in peace with her bad memories for the rest of her life. She DID NOT POISON HER KIDS!
That was an unfortunate coincidence, and the kids may had food poisoning but most likely from the foods, not from the washed pan. I assume your mother wasn’t stupid 70 yeas ago, and like anyone else she would wash the pan with water after bleaching. Even if some bleach was left it would probably make food taste bad but not create toxic concentrations of bleach or aluminum compounds. As for aluminum, it does react with bleach though. The reaction is complex but in any case it results in compounds that would have washed with water as jelly-like aluminum hydroxide and the rest will stay as aluminum oxide on the surface of metallic aluminum and protect it from reacting with water and air. Aluminum is not supertoxic, so if she didn’t wash thoroughly the pan and some traces of aluminum hydroxide were still on the surface that would still unlikely create toxic concentrations. Please read this Google search and you may find many interesting reports, opinions and conversations.
http://preview.tinyurl.com/2eo686a
To summarize, bleach has a basic pH and aluminum is not stable at high pH. Normally it would react with sodium hydroxide for example by the following equation:
Al + NaOH --> Na₃AlO₃ + H₂
Na₃AlO₃ is a water soluble compound and will be washed out. In a case of bleach hydrogen will not form but aluminum will still react
Al + NaClO + H₂O = Al(OH)₃ + NaCl
Bleach usually contains extra base, so insoluble Al(OH)₃ may actually dissolve
Al(OH)₃ + NaOH = Na₃AlO₃ + H₂O

If it wasn’t dissolved then Al(OH)₃ will form, and it will be washed out as a gel from the surface.
After bleach treatment aluminum may look dark or even black. That may make her to think that something was wrong. The dark color is because the protective aluminum oxide layer became actually thicker and it absorbs, traps and holds irreversibly any colored compounds that happened to be around at the time of building that oxide layer.
This is my speculation because aluminum gets colored this way with common dyes. The exact reason why aluminum gets dark color is very puzzling. Possibly it reduces carbon dioxide or some other carbon compounds to carbon and it gets trapped in the protective Al₂O₃ layer. In any case it’s not poisonous and in fact protects aluminum from further corrosion.
I hope I expressed enough my expert opinion on the subject and your mother shell live her life happy.

Aluminum Reaction with Bleach: Sodium hypochlorite (NaOCl) in bleach can react with aluminum, producing aluminum oxide (Al₂O₃) and potentially chlorine gas (Cl₂). This reaction primarily affects the surface of the aluminum, causing corrosion and discoloration, but it's not usually harmful to humans if the pan is rinsed properly.

Don't answer 14 year old threat.