Conductivity and Brine for Dummies

example graph of salinity vs. conductivity 

We know it seems as if we harp on the topic a lot at the Antisocial Network – about a quarter of our DotD nominees are flagged for scientific illiteracy – but we think it's important that people who know nothing about science learn about it before writing about it. Too many content farmers display their ignorance of even basic principles, and we're here to point it out... point out writers like Micah McDunnigan of Sciencing.com (shouldn't that be Ignorancing.com?), who tried to explain "Brine Vs. Conductivity" back in the eHow.com days... and failed

So let's get the basics out of the way: the OQ, in all probability, was interested in the relationship between the salinity of a brine and its conductivity. In fact, conductivity is often used as a proxy for salinity, which is how the latter is measured. There are other factors, of course, including temperature... but let's see what McDunnigan had to say:

"Conductivity is a measure of a material's ability to carry an electrical current. Conductivity can also be measured for substances such as saline water, or water with significant salt content."

Umm, yeah, we guess... it's just that saline water doesn't necessarily include what Micah considers "salt" (the stuff on your kitchen table). Weak introduction, Micah, weak. Moving on, McDunnigan tells us that

"The term saline indicates the presence of concentrations of dissolved inorganic ions, such as salt. The relative magnitude of this concentration determines the salinity of the water." Err, Micah, "salt" isn't an inorganic ion. Sodium, yes; chlorine, yes; salt, no. If you meant "dissolved salts," you should've said that; assuming you knew what "dissolved" and "salts" mean, which is not a safe assumption. And then there's "Brine is water that is heavily saturated with inorganic ions, or salts. By definition, a saline solution becomes brine when its salt concentration hits 45,000 milligrams per liter."

Unfortunately, Micah falls victim to assuming that his (one) reference is authoritative; it's not -- the definition of "brine" typically depends on context: brine to a chef is different from brine to a marine biologist. Finally, McDunnigan has his big reveal:

"The salt concentration in water determines its conductivity. The greater the salt concentration, the higher the conductivity. Brine, having the largest concentration of salts, consequently has the highest conductivity."

Well, yeah, Micah, we kinda already knew that; though we find it interesting that 1) you said exactly zilch about why that's the case, and 2) you failed to suggest any sort of relationship between the two quantities; much less suggest that relationship can vary depending on temperature, pressure, and the dissolved ions. In other words, you did a lousy job, hence your award: the Dumbass of the Day (again).

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