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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: nature boy on April 27, 2011, 08:59:18 AM

Title: NaOH and plastics
Post by: nature boy on April 27, 2011, 08:59:18 AM
Hello to everyone!
I mix 33% NaOH solutions with table salt and pure lemon juice. I used a kitchen inox long rod for stirring. After about 15-20 different mixtures, the last time when i washed the rod with tap water immediately turned grey (only the surface that was in the solution). It looks like it corroded - can't glaze it with detergents. Contrary, the inox mixing pot still stays always in good condition (after more than 100 solutions).
I learned that thick plastics are more resistant with NaOH solutions.
Is it true? What kind of plastics is more durable and safer with NaOH solutions?
Thank you.
Title: Re: NaOH and plastics
Post by: JustinCh3m on April 27, 2011, 01:29:04 PM
As a lab instructor, I always inform my students to store NaOH in the plastic, polyethylene bottles (with cap).
Title: Re: NaOH and plastics
Post by: SirRoderick on April 27, 2011, 03:56:34 PM
Why are you mixing NaOH with lemon juice? That would just neutralise the acid.

Inox can be corroded by chlorine. I think it reacts with the chromeoxide, Perhaps the tap water contains enough of it to affect the rod? Anyway, plastic is a good recipient for NaOH.
Title: Re: NaOH and plastics
Post by: DevaDevil on April 27, 2011, 03:57:06 PM
As a lab instructor, I always inform my students to store NaOH in the plastic, polyethylene bottles (with cap).

indeed, NaOH solutions will corrode glass slowly
Title: Re: NaOH and plastics
Post by: nature boy on April 27, 2011, 04:23:00 PM
Why are you mixing NaOH with lemon juice? That would just neutralise the acid.

Inox can be corroded by chlorine. I think it reacts with the chromeoxide, Perhaps the tap water contains enough of it to affect the rod? Anyway, plastic is a good recipient for NaOH.

I am mixing NaOH with lemon juice to make a secret solution...  8)
Thank you all for your replies.
Also i found this helpful web page:
http://www.nalgenelabware.com/techdata/Chemical/index.asp
Title: Re: NaOH and plastics
Post by: SirRoderick on April 27, 2011, 04:25:58 PM
Well your "secret solution" would be the same without the lemon mate. Unless you're using it for the smell of course.

Also I just realised that you said "table salt". Duh, that's your Chlorine right there. It's reacting with your inox.

Anyway, so use glass and all will be well.
Title: Re: NaOH and plastics
Post by: enahs on April 27, 2011, 04:28:29 PM
Your secret solution is Sodium Acetate if you remove the water. Nothing secret about that.

I mean, it sounds to me like you are trying to make a salt that has a vinegar taste to it.

Which is awesome tasting, by the way.

But you can buy it in stores now, FYI.

Also, if you really want to do it at home (I have even done it too), I find that malt vinegar is the way to go instead of lemon juice. That extra malt flavoring really sets off the seasoning when you are done. So good on french fries, salty malt vinegar!!!!
Title: Re: NaOH and plastics
Post by: nature boy on April 27, 2011, 05:01:47 PM
Your secret solution is Sodium Acetate if you remove the water. Nothing secret about that.

I mean, it sounds to me like you are trying to make a salt that has a vinegar taste to it.

Which is awesome tasting, by the way.

But you can buy it in stores now, FYI.

Also, if you really want to do it at home (I have even done it too), I find that malt vinegar is the way to go instead of lemon juice. That extra malt flavoring really sets off the seasoning when you are done. So good on french fries, salty malt vinegar!!!!

Wrong. I will keep the secret ! :-X ;)

Well your "secret solution" would be the same without the lemon mate. Unless you're using it for the smell of course.
No. It will not be the same.

Also I just realised that you said "table salt". Duh, that's your Chlorine right there. It's reacting with your inox.

I found that this is true. Thank you mate!
Title: Re: NaOH and plastics
Post by: Borek on April 27, 2011, 06:18:44 PM
Also I just realised that you said "table salt". Duh, that's your Chlorine right there. It's reacting with your inox.

That's chloride, not chlorine.
Title: Re: NaOH and plastics
Post by: Borek on April 27, 2011, 06:20:44 PM
Your secret solution is Sodium Acetate if you remove the water.

More like sodium citrate  :P
Title: Re: NaOH and plastics
Post by: enahs on April 27, 2011, 06:22:28 PM
Your secret solution is Sodium Acetate if you remove the water.

More like sodium citrate  :P

Citric acid, acetic acid. Taste the same to me in the sodium form! But good point! heh
Title: Re: NaOH and plastics
Post by: SirRoderick on April 27, 2011, 06:23:55 PM
Also I just realised that you said "table salt". Duh, that's your Chlorine right there. It's reacting with your inox.

That's chloride, not chlorine.

Is it? Ah, well English isn't my native language so I'll take your word for it.
Title: Re: NaOH and plastics
Post by: DevaDevil on April 29, 2011, 01:06:22 PM
Also I just realised that you said "table salt". Duh, that's your Chlorine right there. It's reacting with your inox.

That's chloride, not chlorine.

Is it? Ah, well English isn't my native language so I'll take your word for it.

chlorine = Cl2, chloride = Cl-

if you ever want to be involved in chemistry, you do well to remember this, as it is the way to distinguish in language between the element and ion in halogen compounds:

Fluorine = F2, fluoride = F-,
etcetera
Title: Re: NaOH and plastics
Post by: SirRoderick on April 29, 2011, 03:20:29 PM
Also I just realised that you said "table salt". Duh, that's your Chlorine right there. It's reacting with your inox.

That's chloride, not chlorine.

Is it? Ah, well English isn't my native language so I'll take your word for it.

chlorine = Cl2, chloride = Cl-

if you ever want to be involved in chemistry, you do well to remember this, as it is the way to distinguish in language between the element and ion in halogen compounds:

Fluorine = F2, fluoride = F-,
etcetera

I see, thank you. I will remember that.