Metal finishing Q&As since 1989
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How I can determine Saccharin by classic volumetric titration?
Q. Indeed I am working on a project about electroplating systems. My work is about determination of some compounds which are used in electroplating baths, such as saccharin, 1-Benzyl-3-carboxypyridinium chloride, pyridinium-1-propane-3-sulfonate.
Because we can buy the instrument same as HPLC or other I want to find a classic method same as simple volumetric titration.
I found some method for determination saccharin but with information that has been mentioned in article I was not successful in determination.
Would you please help me and introduce some methods!
Thank you again for your time and consideration. I greatly appreciate your generosity.
Researcher - Tehran, Iran
February 25, 2011
A. If the saccharin concentration is similar to a Watts bath, this will work-
Add 50 mL bath sample + 35 mL ethyl acetate + 1 mL conc. HCl to a separatory funnel. After standard extraction procedure, quantitatively transfer the ethyl acetate layer to an Erlenmeyer flask. Add 20 mL of methanol
[affil links]+ a dropper-full of bromocresol purple
[on
eBay or
Amazon]
indicator. Titrate with 0.1N NaOH [on
eBay or
Amazon]
to blue. You'll want to use an experimental factor for the determination rather than the mathematical equivalence.
Jon Barrows, MSF, EHSSC
GOAD Company
Independence, Missouri
Q. Bromocresol purple vs. phenolphthalein as indicator for Saccharin analysis?
We use similar method for determination of saccharin, but we use a different indicator (Phenolphthalein).
Today I made 2 analyses, one with bromocresol purple
[on
eBay or
Amazon]
as indicator and one with phenolphthalein
[on
eBay &
Amazon]
. But I got different results, about 2 ml difference. So now I'm not sure which one is more accurate.
- Bovec, Slovenia
August 29, 2014
A. I will bet that the BCP is closer to the correct answer. It changes color in the 4-5 Ph area which is extremely close to 7 as far as the amount of titrant it takes. phenolphthalein changes color in the 8 - 10 range, and more commonly closer to the 10 range. That means that part of the titrant is probably dropping out some of the metal that MIGHT be in the solution.
phenolphthalein is a lousy indicator for a plating chemist.
- Navarre, Florida
Q. Okay, now I will do analysis with both indicators and then will decide which one I will choose. I also prefer BCP -- it has more visible end point from violet red to blue colour.
I have another question regarding saccharin determination:
Last week I added additive which contains saccharin to nickel bath; two days later I made analysis and the consumption of NaOH was the same as before I added the additive. Don't understand that. Has anyone had the same experience like this?
- Bovec, Slovenia
August 31, 2014
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