# Salinity Calculator

Calculate Salinity from electrical conductivity and temperature of a solution:

Use the following calculator to calculate Salinity from electrical conductivity for any solution. The Salinity range for this calculator is from S = 2 to S = 42.

Lab Procedure:
1. Measure temperature of sample in Celsius degree (C)
2. Measure the electrical conductivity (in uS/cm) of the same sample using conductivity meter at specified temperature in step 1.
3. Enter temperature (C) and electrical conductivity (uS/cm) in the following calculator.
4. Press recalculate button to calculate Salinity.

Note: Most types of conductivity meters measure both conductivity and temperature using the same probe. Almost all of them are measuring conductivity and making correction by temperature correction factor (~2.5% for each degree) to standard temperature 25 C degree. i.e. if you are using those types of equipment then use standard temperature 25 C in the following calculator.

Questions:

What is Salinity stand for?
Salinity is an important unitless property of industrial and natural waters. It was originally conceived as a measure of the mass of dissolved salts in a given mass of solution.

What is the Salinity measuring unit?
The commonly used unit is Practical Salinity Unit (PSU), and another unit called PPT (part per thousands)

How to measure Salinity of sample?
The most accurate method to measure salinity is by measuring electrical conductivity of a solution at specific temperature (t) and substitute values in the following equation:

Where
S: is the practical Salinity scale (PSU)
Rf: Conductivity ratio
t: temperature of solution in Celsius degree (C)

Values a0 to a5 and b0 to b5 all are constants
C (Sample at t) (uS/cm): conductivity of sample at specific temperature t
C (Kcl solution at t)(uS/cm): is a measure of the conductivity of KCl solution containing a mass of 32.4356 g KCl in a mass of 1 kg of solution, the solution has a Salinity of 35 PSU at 15 C degree. It can be measured also using the following equation:

C (Kcl solution at t)(uS/cm) = -0.0267243 x t3 + 4.6636947 x t2 + 861.3027640 x t + 29,035.1640851

Example: when KCl solution’s temperature is 18 C then we calculate the solution conductivity as follows:

C (Kcl solution at t)(uS/cm) = -0.0267243 x (18)3 + 4.6636947 x (18)2 + 861.3027640 x (18) + 29,035.1640851
= 45893.8 uS/cm

This equation generated from 37 readings of the same solution at different temperatures from 0 to 37 C degree. See Figure A below

Figure A: Conductivity of reference KCl solution at various temperatures

Reference
Standard Methods for the Examination of Water and Wastewater, 20th edition, 1999.

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