Ionode IJ pH V5.1 Bedienungsanleitung PDF herunterladen (Seite 15)

Ionode IJ Instruction Manual 15

further details, please contact Ionode specifying

make and model of pH/mV meter or titrator.

Sodium Error

The selectivity of H

over Na

is extremely high,

but small errors become apparent at high pH

(i.e. low H

concentration) and high Na

concentration.

The pH glass used in the IJ44C has a very low

sodium error. Corrections to the measurement

can be made if the sodium concentration of the

sample is known. There are typical sodium

errors for a new IJ44 pH electrode (see Graph

1). The sodium error increases with aging.

A measured pH can be corrected by locating it

on the x-axis and drawing a line straight up until

it intersects the sodium concentration line of the

sample (extrapolate between lines for sodium

concentrations not drawn). Draw a line from the

intersection directly over to the y-axis to

determine the error in the measurement. The

actual pH of the sample is determined by

adding the error to the measured pH. For

example, if a sample with 1M Na

concentration

measures pH 12.6, then the actual pH is 12.77.

The sodium error is larger in the “A” glass pH

electrodes. As a consequence, “A” glass pH

electrodes are best suited to pH measurements

below pH12. The “A” glass would be preferred

for measurements in strong acids, titrations and

for measurement in lower conductivity samples.

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Ionode IJ pH V5.1 Bedienungsanleitung Seite 15