Natural Seawater Scale (Unesco 1966); Practical Salinity Scale - Hanna Instruments HI98192 Instruction Manual

For practical reasons, the salinity of a solution is derived from the salinity of the seawater. Two methods
of calculating the salinity from the conductivity are supported:
• Natural seawater scale

• Practical salinity scale

Natural seawater scale (UNESCO 1966)

According to the definition, salinity of a sample in ppt is calculated using the following formula:
C (sample)
R =
T
C(35;15)·r
T
T
r =1.0031·10 T –6.9698·10
‑9 4
T
R=R +10 R (R –1.0)(T–15.0)[96.7‑72.0R
‑5
T T T
S=‑0.08996+28.2929729R+12.80832R
where:
R ‑ coefficient;
T
C (sample) ‑ uncompensated conductivity at T °C;
T
C(35;15)= 42.914 mS/cm ‑ the corresponding conductivity of KCl solution
containing a mass of 32.4356 g KCl / 1 Kg solution;
r ‑ temperature compensation polynom.
T
Note: The formula can be applied for temperatures between 10 °C and 31 °C.
To access this range press Mode while in Salinity range until the seawater scale [SW] is
displayed.
Practical salinity scale
This is a practical scale based on the precise measurement of the electrical conductivity of a solution
with a known salinity range.
The relationship derived from the scale relates salinity, conductivity, temperature and pressure
and use a solution with a salinity of 35 ‰ as datum point. This is taken to have a conductivity
of 42.914 mS/cm of 15 °C at standard atmospheric pressure.
T +1.104259·10 T +2.00564·10
‑7 3 ‑4 2
+37.3R –(0.63+0.21R
2
T T
–10.67869R
2
T+6.766097·10
‑2
)(T–15.0)]
2
T
+5.98624R –1.32311R
3 4 5
‑1
11