Re: pH meters

From: Sandy King <sanking@clemson.edu>
Subject: pH meters
Date: Wed, 03 Mar 2004 18:13:03 -0500

> Is there a common household substance that can be used to verify the
> accuracy of readings of these meters, and/or calibrate them?

You can look up NIST and NBS standard buffer formulations.

My web page describes two of them. One is 0.01M borax for pH of 9.18
and another carbonate/bicarbonate for pH of 10.01. These are easy to
make out of common ingredients though if you want accuracy, you must
use AR grade and deionized water. My particular box of 20 Mule Team
borax is reasonably accurate but I wouldn't calibrate with it.

The standard pH 4 buffer is phthalate buffer; the pH 7 is phosphate
buffer.

All these solutions need to be used at 25C if you want nominal pH value.

--
Ryuji Suzuki
"All the truth in the world adds up to one big lie." (Bob Dylan 2000)