Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: znaes97 on December 01, 2022, 11:19:07 AM
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Hey everybody,
I have a procedure to check for the presence of chlorine in waste water. The procedure says to use a sodium acetate buffer. Does it have to be sodium acetate or can we use something else like an ammonium acetate buffer? Any help is greatly appreciated.
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A sodium acetate buffer contains the equal moles of sodium acetate and acetic acid. The concentration and the to achieve pH you have to know. Calculation with Hendersson Hasselbalch equation.
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The procedure doesn't say anything about concentration. It just says "moisten a strip of potassium iodide starch paper with the sodium acetate buffer." A little more detail about the procedure, it is a two part check for cyanide in waste water. The first check is for chlorine and the second is for sulfide. Both checks require the sodium acetate buffer.
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I would suggest to use a 0,1 M buffer. 0,05 M CH3COONa and 0,05 M CH3COOH
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Procedure as worded is ambiguous - acetate buffer means a buffer made by mixing acetic acid with some acetate (typically sodium), but what are concentrations of these and what is their ratio is in no way obvious. Acetate buffer typically means something between pH 4 and 5.5, exact value can be important, or it can be not, depends on the reaction details.
Buffer has to be selected carefully, so that it doesn't interfere with the detection reaction. Say, if you detect chlorides with Ag+, any ion reacting with Ag+ will give you a false positive. Acetate buffer is a common selection in such cases.