User Guide

GENERAL INFORMATION:
The pNa tester utilizes a sodium ion-selective elec-
trode to determine the activity of free sodium in
solution.
pNa = -log a
Na
In dilute solutions, the activity coefficient is nearly 1
and in such solutions pNa is a good indicator of the
sodium ion concentration. The relationship between
the pNa scale and the g/L Na
+
scale is explained
in the chart below.
A double junction reference is used to ensure a
highly stable reading. If you suspect that the
calibration has drifted, you can recalibrate the
meter by using a solution of known concentration.
Adjust the reading with the calibration trimmer.
HOW TO USE THE CHART:
• Locate the pNa reading on the horizontal axis of
the chart.
• Move vertically upwards to intersect with the 45º
line.
• Move horizontally and read the g/L Na value.
E.g. pNa = 1.4
g/L = 0.9
OPERATION:
• Remove the protective cap and turn
the meter on with the ON/OFF switch
located on the top.
• Immerse it in the solution to be tested
without exceeding the maximum im-
mersion level.
• Stir gently and wait for the reading
to stabilize.
• The reading on display is directly
expressed in pNa unit. Use the chart
below to change the value from pNa
to g/L.
• After use, switch the meter off and rinse the
electrode with water to minimize contamination.
Always replace the protective cap after use.
• Large differences in pNa readings (±0.5 pNa)
could be due to a dry electrode or lack in
calibration.
• To improve performance, immerse the meter in
HI7080 solution up to the maximum immersion
level at least once a week.
pNa
HI98202
Soft Water Tester
Manufacturers since 1978