http://braukaiser.com/wiki/index.php?action=history&feed=atom&title=2_point_calibration_formula 2026-09-24T00:33:01Z Revision history for this page on the wiki MediaWiki 1.24.1 http://braukaiser.com/wiki/index.php?title=2_point_calibration_formula&diff=1863&oldid=prev 2008-04-22T19:11:47Z

<p></p> <p><b>New page</b></p><div>When the pH meter doesn’t calibrate anymore or is only capable of a single point calibration, the following formula can be used to calculate the pH from the measurements of calibration buffer solutions<br /> <br /> &#039;&#039;&#039;&lt;tt&gt;pH&lt;sub&gt;x&lt;/sub&gt; = pH&lt;sub&gt;ref1&lt;/sub&gt; + (pH&lt;sub&gt;ref2&lt;/sub&gt; – pH&lt;sub&gt;ref1&lt;/sub&gt;) * (M&lt;sub&gt;x&lt;/sub&gt; – M&lt;sub&gt;ref1&lt;/sub&gt;) / (M&lt;sub&gt;ref2&lt;/sub&gt; - M&lt;sub&gt;ref1&lt;/sub&gt;)&lt;/tt&gt;&#039;&#039;&#039;<br /> <br /> * pH&lt;sub&gt;x&lt;/sub&gt; - the pH of the sample<br /> * pH&lt;sub&gt;ref1&lt;/sub&gt; - the pH of the calibration buffer 1 (generally 4)<br /> * pH&lt;sub&gt;ref2&lt;/sub&gt; - the pH of the calibration buffer 2 (generally 7)<br /> * M&lt;sub&gt;ref1&lt;/sub&gt; - the measured value for buffer 1<br /> * M&lt;sub&gt;ref2&lt;/sub&gt; - the measured value for buffer 2<br /> * M&lt;sub&gt;x&lt;/sub&gt; - the measured value for the sample<br /> <br /> When using 4 and 7 pH buffer solutions, the equation simplifies to<br /> <br /> &#039;&#039;&#039;&lt;tt&gt;pH&lt;sub&gt;x&lt;/sub&gt; = 4 + 3 * (M&lt;sub&gt;x&lt;/sub&gt; – M&lt;sub&gt;4&lt;/sub&gt;) / (M&lt;sub&gt;7&lt;/sub&gt; - M&lt;sub&gt;4&lt;/sub&gt;)&lt;/tt&gt;&#039;&#039;&#039;<br /> <br /> But most pH meters will do this automatically and such complicated calculation is not necessary.</div>

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