Yamato WA500, Instruction Manual

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-32-
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Indication of Water Quality
Electric conductivity
●
Electric conductivity shows how much electricity can pass. As water contains more electrolyte or
impurity, more electricity can pass through and the value of conductivity gets larger. On the contrary,
the value gets smaller as water contains less electrolyte.
●
That means water is more pure as the conductivity is smaller.
However, the value of conductivity shows containment of electrolyte only but does not indicate any
containment of non-electrolyte such as organic, colloid, dissolved gas and microorganism. Therefore,
conductivity is just one of indicators to show water purity.
●
Resistivity is to indicate the same property as the electric conductivity shows. Resistivity is reciprocal
to electric conductivity . The larger resistivity indicates higher purity.
●
To calculate the resistivity from the electric conductivity;
R=Resistivity
ρ
=Electric conductivity

R［Ω･m］
1
S m］


[ /
or R［×10 Ω･m］
1
×10 S m］
４
－４


[ /
Pure water theoretically has the following value.
R=18.3
×
10
4 Ω･
m(18.3M
Ω･
cm)25
℃
(This unit display the integral number within 18 to 1
×
10
4
Ω･
m. Note there is no decimal number
indication.)
ρ
=0.055
×
10
-4
S/m(0.055
μ
S/cm)25
℃
Quality of ion-exchanged/distilled water
●
Ion-exchanged water and distilled water have the following properties respectively. Select either water
according to your requirement.
It is ideal to use distilled water just after you collect. If you do not use the water soon, drain the distilled
water tank. When you keep distilled water in the tank for a while, drain the tank and store new distilled
water in the tank to use.
(1) Ion-exchanged water
Since almost all electrolyte are removed from ion-exchanged water, you can get water with the lowest
electric conductivity. But it is impossible to remove non-electrolytic impurity. Purity is a little low with a new
resin or at the re-start of flow after operation stops.
(2) Distilled water
The mode can remove averagely electrolyte and non-electrolyte except ammonia and other
substances with low boiling point.
However, water absorbs carbonic acid gas from air and creates carbonic gas during its production
process (in condensation and storage).
Accordingly, water quality is worse than ion-exchanged water and becomes weak acid (pH 5 to 6)
with its electric conductivity about 1 to 2
×
10
-4
S/m 25
℃
(1 to 2.5
μ
S/cm)