chemical storage and reactivity

cfstrick · Post by **cfstrick** » Thu May 03, 2007 12:14 pm

I work at a lab that uses a 2.5% solution of potassium dichromate. Part of our production entails a step using very diluted bleach. Inevitably the two will mix together during production. The mixed liquid waste is stored on site for up to 8 months before being shipped off for disposal. Should I be worried about the two being mixed together and stored as hazardous waste in the same metal drum?

Xen · Post by **Xen** » Fri May 04, 2007 5:38 pm

cfstrick wrote:I work at a lab that uses a 2.5% solution of potassium dichromate. Part of our production entails a step using very diluted bleach. Inevitably the two will mix together during production. The mixed liquid waste is stored on site for up to 8 months before being shipped off for disposal. Should I be worried about the two being mixed together and stored as hazardous waste in the same metal drum?

Common chemical bleaches include "chlorine bleach", a solution of sodium hypochlorite (NaClO), and "oxygen bleach", which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate or sodium percarbonate. Bleaching powder is calcium hypochlorite Ca(ClO)₂.
If your bleach is either NaClO and Ca(ClO)₂ then it would not react with K₂Cr₂O₇.
In the case of peroxide-releasing bleaches the decomposition reaction might be catalyzed and as a result oxygen will be produced.
I would be worried about metal drum though ... is it made for the proper stainless steel? Because strong oxidizers like these significantly speed up corrosion.

cfstrick · Post by **cfstrick** » Sat May 05, 2007 4:11 pm

It is a very dilute Sodium hypchlorite solution (~1.5%) but there is still some gassing off when the two chemicals are mixed and stored together in the 55 gallon drums. As far as I know, the drums are stainless steel, but I am going in to work tonight and will check. This concerns me very much. Unfortunately I work for a highly regarded internaional veterinary pharmaceutical corporation with complete incompetents and I will be damned if I am going to endanger myself or the lives of my coworkers for others' incompetence and ineptitude when it comes to the storage of hexavalent chromium compounds, regardless of how dilute it may be. I need your help soon. I will get back to you on the drum, but I AM 95% CERTAIN IT IS STEEL, but don't know about the grade. I think the shipping stickers are still on them. What grade should it be? Also, any idea on the maximum temperature and time at which this mixture can be stored?

cfstrick · Post by **cfstrick** » Mon May 07, 2007 8:45 am

The steel drums bare stickers that say "UN 1A₁ / X₁.8 / 300 / 05
USA M₄₉₂₁
1.2/ 1.1/ 1.2"
And in white paint they read "TH₅₅-3E"
Is this the right kind of steel for this type of corrosive?

Xen · Post by **Xen** » Mon May 07, 2007 9:56 pm

cfstrick wrote:The steel drums bare stickers that say "UN 1A₁ / X₁.8 / 300 / 05
USA M₄₉₂₁
1.2/ 1.1/ 1.2"
And in white paint they read "TH₅₅-3E"
Is this the right kind of steel for this type of corrosive?

I am not an expert in steel specification either. I would look for something like this in the search engine.

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