Summary for zinc bath titration calculation Discussion
zinc/chloride concentration in a zinc bath by titration is discussed with a practical calculation method from Dave Wichern. He says that if the bath is titrated with 0.1 M EDTA, each liter of titrant complexes 0.1 mole of zinc, which he recalls as 6.54 g Zn. To calculate the zinc content of the sample, multiply the EDTA volume used (in liters) by 6.54 to get grams of zinc in the aliquot, then divide by the aliquot volume (in liters) to obtain g/L zinc. Wichern also cautions against relying on generic factors without understanding the chemistry, noting that mistakes can be disastrous. For the procedure, he describes diluting the bath sample with water, adding pH 10 buffer, then potassium or sodium cyanide, then 10 ml of 10% formalin, and titrating immediately and rapidly with 0.1 M EDTA to the eriochrome black T endpoint.
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Q. Hi, my company suffers the ability to run the maintenance of their existing bath that is, zinc plating bath. Now I put some effort to discovering the step by step method of these analyses using titration approach, but my problem currently is how to conduct the calculation of the analysis.
Salisu Mohammed
plating shop employee – Minna, Niger, Nigeria
October 4, 2011
A. I suppose you are titrating your Zn bath with 0.1 M EDTA.
Each liter of this will complex 0.1 M Zn, which, if memory serves, is 6.54 g Zn.
So: volume titrated (in liters) x 6.54 = g Zn in the aliquot taken for analysis.
Now, divide this number (Zn, in grams) by the volume of that aliquot (in liters) and you will have the Zn concentration, in g/l.
OK?
Good luck. It is always better to work things out, from the beginning, knowing the chemistry. Blindly using some “factor” from somewhere can lead one into disastrous errors. (I know; I’ve made them.)
The way I always did this was to add the plating bath sample to 80 ml or so of water; add the pH 10 buffer; then, about 200 mg of potassium or sodium cyanide. Then, add 10 ml 10% formalin; then, titrate RIGHT AWAY, RAPIDLY, with 0.1 M EDTA to the eriochrome black t
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endpoint.
Dave Wichern
Consultant – The Bronx, New York
Q. Thank you very much Dave, I really appreciate your contribution.Could you please elaborate more on how you come with the value 6.54 that you multiply with the titrant value [i.e the volume titrate].
It might it interest you to have more idea on what I actually did during the titration;
I diluted 5 ml of bath sample with 100 ml deionised water followed by adding buffer solution then I finally added a tip of xylenol orange sodium salt then I titrate immediately with 0.1M EDTA.
thanks again in anticipation.
Salisu Mohammed
– Minna, Niger state, Nigeria
A. 65.4 g/mol Zn x 0.1 mol/l = 6.54 g/l
Dave Wichern
Consultant – The Bronx, New York
Great. Thanks.
Masoud amedi
– Iran.Tehran
May 23, 2023