Saline water


Saline water is water that contains a high concentration of dissolved salts. The salt concentration is usually expressed in parts per thousand or parts per million. The United States Geological Survey classifies saline water in three salinity categories. Salt concentration in slightly saline water is around 1,000 to 3,000 ppm, in moderately saline water 3,000 to 10,000 ppm and in highly saline water 10,000 to 35,000 ppm. Seawater has a salinity of roughly 35,000 ppm, equivalent to 35 grams of salt per one liter of water. The saturation level is dependent on the temperature of the water. At 20 °C one liter of water can dissolve about 357 grams of salt, a concentration of 26.3% w/w.

Properties

NaCl, wt%Freezing point Density Refractive index at 589 nmViscosity
000.999841.33301.002
0.5−0.31.00181.33391.011
1−0.591.00531.33471.02
2−1.191.01251.33651.036
3−1.791.01961.33831.052
4−2.411.02681.34001.068
5−3.051.03401.34181.085
6−3.71.04131.34351.104
7−4.381.04861.34531.124
8−5.081.05591.34701.145
9−5.811.06331.34881.168
10−6.561.07071.35051.193
12−8.181.08571.35411.25
14−9.941.10081.35761.317
16−11.891.11621.36121.388
18−14.041.13191.36481.463
20−16.461.14781.36841.557
26−19.181.1931.37211.676

At 100 °C, saturated sodium chloride brine is about 28% salt by weight. At 0 °C, brine can only hold about 26% salt. At 20 °C one liter of water can dissolve about 357 grams of salt, a concentration of 26.3%.
The thermal conductivity of seawater is 0.6 W/mK at 25 °C. The thermal conductivity decreases with increasing salinity and increases with increasing temperature. The graphs and online calculations in this page plot thermal conductivity for varying salinity and temperature:
The salt content can be determined with a salinometer.
Density ρ of brine at various concentrations and temperatures from 200 °F to 575 °F can be approximated with a linear equation:
where the values of an are:
Weight %a2a3
50.04372.60
100.03973.72
150.03574.86
200.03276.21
250.03077.85

Electrolysis

About four percent of hydrogen gas produced worldwide is created by electrolysis. The majority of this hydrogen produced through electrolysis is a side product in the production of chlorine.