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Gluconate Analysis for Caustic Etch


Does anybody know of an analytical technique for gluconate in the caustic etch used for aluminum? I need something for a plant floor that does not use complex equipment or techniques. Involving a pH meter or colorimeter is OK, but not HPLC, extractions, etc.

Paul Schultz
- Alcoa Center, Pennsylvania


Gluconate is a complexing agent, so how about adding dropwise amounts of ferric chloride or some other compound to a known quantity of sample. Ideally, the iron would become complexed only by the gluconate, in stoichiometric amounts, and perhaps even be its own endpoint?

tom pullizzi monitor
Tom Pullizzi
Falls Township,


Gluconate is a good complexor of transition metals, but it also complexes the aluminum dissolved by the etch (it is there to complex the Al and help prevent the Al sludge from precipitating like concrete). Therefore, titration with iron or other metals would only work if the gluconate complexes the iron or other metal much more strongly than aluminum. Does anyone know if that is the case? Or, is there a way to tie up the aluminum and do a simple acid-base titration for the gluconate endpoint?

Paul Schultz
- Alcoa Center PA


Paul, If you add a certain amount of Na glucoheptonate to tie up the Aluminum than I do believe you can proceed w/ Tom's suggestion of adding known amounts of Ferric chloride to determine the so called "free gluconate" in your bath. I'd run a blank w/ and without the glucoheptonate.

One other suggestion would be straight titration w/ perchloric acid however you need to make the solution neutral This procedure can be found on the American Pharmacopoeia for Gluconate - Just follow the bouncing ball.

Good Luck

Domingos J C Spinelli
- SP Brazil


Gluconate can be titrated by periodat (marplade titration). Take 0.5 cc of filtered etch bath dilute by 100 cc dw add fk and by CLH neutralize it by phenolphetalein. Any S or SO2 from your etch will be removed , then make solution slightly acidic to prepare for periodate titration . Titration is the same for glycerotitration is blank type.

Hadi Khosravi
- Tehran, Iran


Analysis method for sodium gluconate concentration. I'm looking for an analysis method for determining the concentration of sodium gluconate in a mixture with sodium hydroxide. The sodium gluconate is to be 25 to 50 g/l and the sodium hydroxide is to be 75 to 150 g/l.

William L. Glass
- Paramont, California, USA

January 27, 2009 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Does anybody know of an analytical technique for gluconate in the caustic (sodium hydroxide)

vahida huseljic
- Tuzla, Bosnia and hercegovina

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