I'm not a chemist by profession, so please forgive any syntactical or vernacular oversights on my part. Basically, I'm getting mixed messages from different sites about the density of sodium chloride. Wikipedia and some other sites list the density as $2.16$ or $\pu{2.17g/cm^3}$, while other sites list it as $\pu{1.199g/ml}$. Paradoxically, this one lists it as both:


Would someone be kind enough to point out what I am missing, please? I have reagent-grade NaCl that I need to measure accurately in order to obtain a correct weight/volume percentage. Thanks

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    $\begingroup$ The CRC Handbook of Chemistry and Physics (75 ed) gives values as $2.1634\pm 0.002$ measured by x-ray crystallography and 2.1654 in another table with unspecified method so these values rounded give your first two values. The third value (1.19 ) seems to be wrong. $\endgroup$ – porphyrin Sep 23 '18 at 9:11
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    $\begingroup$ If $\pu{1.199 g cm^−3}$ would be the correct density if sodium chloride, it would float in a saturated solution of itself in water at $\pu{20 °C}$. Since this is not the case this value must be wrong. $\endgroup$ – aventurin Sep 23 '18 at 9:50
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    $\begingroup$ There is a simple explanation: one density is the density of the pure substance; the other is the density of the container with imperfectly packed crystals of the substance (so the overall density contains a lot of air because the crystals don't pack tightly). The second matters to shippers; the first to chemists. $\endgroup$ – matt_black Sep 23 '18 at 10:39
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    $\begingroup$ I'm almost certain the value of 1.199 g/mL refers to the density of a saturated aqueous solution of NaCl. See for example this data sheet. This kind of thing happens a lot in sites which just scrape whatever property values they can find and don't do any sanity checking. $\endgroup$ – Nicolau Saker Neto Sep 23 '18 at 11:18
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    $\begingroup$ Dead Sea water has an density of $\pu{1.24 g cm^-3}$. Also no reports about saltbergs from there. ;-) $\endgroup$ – aventurin Sep 23 '18 at 13:42

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