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Chapter 7 Reference
7.1 Conductivity measurement
DS-51
71
Chapter 7
Reference
This chapter provides a simple compilation of information for those who
would like to know about the functions of the main unit of the COND
meter and other measurement principles in greater detail.
It also serves as a reference for spare and optional parts.
・
pH 7 standard solution
・
0.025 mol/L potassium dihydrogen phosphate
・
0.025 mol/L sodium dihydrogenphosphate aqueous solution
7.1
Conductivity measurement
●
Electrode sensitivity check
The cell constant of a conductivity electrode may vary, depending on the
sample solution. Check the cell constant by measuring conductivity,
using the following solutions, at least once every three months.
Prepare the potassium chloride standard solution (KCl 0.01 mol/L) using
the procedure below.
In addition, if an error of 5% of more compared to the above values
occurs, calibrate the cell constant (See page 19).
●
Preparing potassium chloride standard solution
How to prepare solution
Dry the potassium chloride powder ("superior quality" commercial
potassium chloride or better) for two hours, at 105 ºC, then cool it in a
desiccator. Measure out the above-listed amount of potassium chloride
into a beaker and dissolve it in de-ionized water. Then, pour into 1-liter
volumetric flask and add de-ionized water until the indication line.
Cell constant
Corresponding
model
KCl
standard
solution
KCl
Weight
Solution
temp.
Conductivity
value
SI units 100 m
-1
(former unit designa-
tion 1 cm
-1
)
9382 -10D
0.01
mol/L
0.7440 g
0ºC
77.4 mS/m
(0.774 mS/cm)
18ºC
122.0 mS/m
(1.220 mS/cm)
25ºC
140.8 mS/m
(1.408 mS/cm)