### chloride, adjusted for the absolute difference between sodium and chloride

Chloride is arguably the most underestimated quantity in clinical acidbase practice.
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Because electroneutrality has to be maintained, reducing the difference between the two main ions in extracellular fluid, Na^{+} and Cl^{-}, one positive, the other negative,
necessarily narrows the space left over for the second most common negative ion species: HCO_{3}^{-}.

As long as PCO_{2} remains unchanged, the classical Henderson -Hasselbalch- equation tells us that the solution will become more acidotic.

As it is the difference between the two, Na^{+} and Cl^{-}, that matters and not their absolute values, Cl^{-} gets adjusted for any concomitant changes in
Na^{+} by simple addition and subtraction: *Cl*_{corr}

(Deriving Cl_{corr} by its change proportional to that of Na^{+}, is preferred when looking for concentrational and dilutional effects.)

### consult the glossary for other aspects of acid-base equilibria and the rules and mathematics behind our website:
Glossary