Weight share of solid particles (usually salt) in fluid or soil.

It is normally measured as the ratio of salt weight to pure fluid/soil weight:

(1)	$\begin{array}{l}\displaystyle {\rm Sal} = \frac{\mbox{mass}_{\mbox{salt}}}{\mbox{mass}_{\mbox{pure fluid/soil}}}\end{array}$

Symbol

Dimension

SI units

Oil metric units

Oil field units

Additional

Sal

–

‰

frac = 10^-3 ‰ = 10^-6 ppm

‰ = ppk = ppt = 1,000 ppm

wt% = 0.01 frac = 0.1 ‰ = 100 ppm

^[1] g/L = 10^-3 frac = 10^-5 wt% = 1 g/kg = 1 ‰ = 10³ mg/L = 10³ ppm

^[2]mg/L= 1 ppm = 0.01 wt% = 0.001 ‰

^[1],^[2]: In engineering practice, the Salinity is often measured in [ g/L ] and [ mg/L ] as equivalent of ppk and ppm correspondingly.

But this is a misnomer as these units have a physical meaning of density while the standard Salinity measure is a dimensionless quantity and frac, wt%, ppk and ppm should be used instead.

The equalities ^[1] and ^[2] take the true meaning only when non-saline fluid has a density of 1 kg/L which is close to the distilled water density at Standard Conditions (0.9991 kg/L).

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