Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: PhuongHuy108 on November 18, 2010, 10:32:37 PM
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Hi all, I'm a newbie in this forum. Today I have two questions
1. Why do you use two standards to calibrate the pH meter?
2. why do we should always use the pH 7 buffer for the first point of the calibration ?
Please forgive me if I have some errors in my post.
:)
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Hi all, I'm a newbie in this forum. Today I have two questions
1. Why do you use two standards to calibrate the pH meter?
2. why do we should always use the pH 7 buffer for the first point of the calibration ?
Please forgive me if I have some errors in my post.
:)
1. Usually you use 2 or MORE standards to calibrate a pH-meter. With one point calibration you cam overlook the moment when you electrode is damaged or lost it efficiency.
2. You do not have to use buffer pH7 as the first point.
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One point doesn't tell a slope.
While Stepan is right that you don't have to start with 7.00, it is a common procedure. Can't think of any rigid logic why it is better to start with pH 7 (unless that's dictated by pH meter, some use automatic calibration procedures and expect you to start with neutral buffer).
http://www.ph-meter.info/pH-electrode-calibration