pH Calibration Buffers
pH probes require periodic calibration. Calibration is done by placing the probe
tip in a small amount of buffer solution of known pH and then adjusting the pH meter
until the pH value displayed matches that of the pH of buffer.
The photo shows two different types of pH buffer: a single-use packet and bottles,
from which small quantities (about 5 ml) are withdrawn for calibration. The single-use
packets are almost certainly more accurate, but they're also more expensive: The
bottled buffers were $5.00 each at a local hydroponics shop. The packets sell for
about one dollar each. In my experience, the bottled buffers work fine.