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topic 42787

Titration procedure for oxalic acid anodizing bath


A discussion started in 2000 but continuing through 2019

2000

Q. Can anyone give me a titration for determining the oxalic acid concentration in a sulfuric/oxalic anodizing bath? Also...will the addition of oxalic acid affect my results when performing the titration for sulfuric acid? Any help would be greatly appreciated.

Marc Green
Marc Green
anodizer - Idaho


2000

A. Dear Marc: From Langford and Parker, "Analysis of Electroplating and Related Solutions" [linked by editor to info about book at AbeBooks], dilute a sample 10ml in a 100 ml volumetric flask using water. Pipet 10 ml of that diluted sample into a boiling flask, add 50 ml water and 25 ml of 50% sulfuric acid. Heat to 65-70 degrees C and titrate with N/10 KMnO4. 1 ml N/10 KMnO4 x 6.3 = g/l oxalic acid. You can test in your own laboratory if additions of oxalic acid will affect your sulfuric acid titration.

tom pullizzi monitor
Tom Pullizzi
Falls Township,
   Pennsylvania 


2000

A. I would add to Tom's remarks that oxalic and sulfuric acid will titrate together in a simple acid-base titration, so your best bet is to determine oxalic acid with permanganate and then subtract it from your total acid result.

As for the acid-base titration: If the concentration of oxalic acid is high, you may be able to see a small inflection point between the first part of a potentiometric-end point titration curve - which includes all of the sulfuric acid and half of the oxalic acid - and the second part, which is due to just the second half (2nd proton) of the oxalic acid.

You may be able to get better separation of the two parts by adding methanol or ethanol to your sample. I don't think an indicator method has any chance. A thermometric titration may work though (see my answer to letter 4626).

Emanuel I. Cooper
- Yorktown Heights, New York


2006

Q. Hi there
I am a student doing chemistry a2 individual investigation and I was given oxalate and manganate to investigate. I am preparing to investigate the rate of reaction of factors affecting such as concentration of potassium manganate (VII), concentration of oxalic and sulphuric acid, and the type of acid used, H2S04 and H3P04. I will also investigate effect of temperature.

However I need some help please. I am planning to do a titration by titrating the potassium manganate into the oxalic acid. however I can't find a method,can anyone provide me with one? how do I make a standard solution with the oxalic acid? also how does this relate to the rate of reaction since the purpose of a titration is to find the concentration of a substance.

any help will be much appreciated.

regards,

Adma Silan
n/a - London, UK



To minimize your searching efforts and to offer multiple viewpoints, we've combined some threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.



Oxalic acid titration

2006

Q. Hi

I need an instruction on how to make an analyse of an oxalic acid electrolyte used in an anodizing setup. Also I need to be able to check the aluminium content of the solution. I found some answers in this forum, but I'm not much of a chemist freak, so I need a simple step by step instruction. What chemicals and indicators etc to use.

Any input on this would be highly appreciated.

Martin Dehlin
- Eksjö, Sweden

2006

A. Hello,
here is my method to make the weekly analysis of my anodizing bath

Sulfo - Oxalic anodization bath

Preliminary :
Pipette 10 cc of the bath in a gauged balloon flask of 100 cc. Complete up to 100 cc with demineralized water. = The mother solution

1) Oxalic Dosage:
pipette: 10 cc from the mother solution and poor it in an Erlen of 300 cc
+ 50 cc of demineralized water
Add + 3 à 5 cc .pure sulfuric acid.(96%) Attention hot!.
Titrate with Potassium Permanganate N/10 -> rose persistent color

2) Free Sulfuric dosage :
10 cc of the mother solution -> Erlen. of 300 cc. + 50 cc demineralized water.
+~ 1 g. potassium fluoride pure. Mixed for complete dissolution.
+ 3 à 5 drops of bromothymol blue. (if powder : some grains)
Titrate by NaOH N/1 -> bleue color.

3) Dosage of dissolved Aluminium :
10 cc of the mother solution -> Erlen of 300 cc.
+ 50 cc demineralized water + Bromothymol blue
Titrate with NaOH N/1 -> persistent blue color

Calculation :

Oxalic A ..... cc x 6.3 = _____ g/l


Free Sulfuric(10 x B ... cc - A ... cc) x 4.9 = _____ g/l

Aluminium (C ... cc - B ... cc) x 9 = _____ g/l

Good luck
Best regards,

Paul Moreau
Paul Moreau
aluminum reflectors for lighting - Liège, Belgium



January 30, 2019

Q. Using the listed titration method we are having a problem with the accuracy of the aluminum concentration in a newly made bath.We analyzed the bath. Initial make up to 5 g/l aluminum. Analysis detected 2.9 g/l. After making another addition which should have doubled the aluminum we got the same 2.9 g/l results.

Frank kar
Anodizing - Passaic, New Jersey, US



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