This question is inspired by another question.

If you take some common salt (NaCl) and some water and mix them, then the volume of the solution is less than the volume of the constituents.

I did some calculations with;

  • 5.75 L salt
  • 44.25 L water
  • total initial volume 50 L

Density of salt is 2.170 kg/L so resulting solution is 22% concentration, which has a density of 1.164 kg/L. Therefore resulting volume is 48.73 L. This means the solution has a volume 1.27 L lower than the constituents.

My question is in two parts;

  1. Are my calculations correct?

  2. Is there another solute that would give a solution with volume 4 L lower than the constituents, given the volume of the constituents must be 50 L.

  • 1
    $\begingroup$ If you consider all kinds of solutes, “the largest reduction in volume when dissolved in water” applies to gases such as $\ce{CO2}$, $\ce{SO2}$, $\ce{HCl}$, or $\ce{NH3}$ (see also fountain experiment). $\endgroup$
    – user7951
    Commented Apr 21, 2016 at 18:11

1 Answer 1


(1) Your calculations are correct.

(2) $\ce{CaCl2}$ has a density of 2.16 kg/L

           kg        vol(L)
  CaCl2    18.00     8.38
  H2O      41.62    41.62
           -----    -----
           59.62    50.00 L

But when dissolved the solution has a density of 1.300 kg/L, so the total volume is 45.86 L. (Data about $\ce{CaCl2}$ solutions.)


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