# Density of saturated KBr

Google search shows the density of saturated $\ce{KBr}$ is $\mathrm{3.119\ g/ml}$ at $\mathrm{25\ ^\circ C}$.

We have a solution of saturated $\ce{KBr}$ and density is about $\mathrm{1.5\ g/ml}$ when weighed on a calibrated analytical balance. How do we account for this discrepancy?

• This is a little off topic, but I just did a google search for 'saturated KBr density' and this question came up. So in a weird paradoxical way, a google search shows it as 3.119g/ml simply because you asked this question :D – N A Feb 17 '16 at 13:50

According to “Aqueous Solubility of Inorganic Compounds at Various Temperatures”, in CRC Handbook of Chemistry and Physics, 90th Edition (CD-ROM Version 2010), David R. Lide, ed., CRC Press/Taylor and Francis, Boca Raton, FL., the solubility (expressed as mass fraction) of potassium bromide $(\ce{KBr})$ in water is $39.4\ \%$ (at $T = 20\ \mathrm{^\circ C}$) and $40.4\ \%$ (at $T = 25\ \mathrm{^\circ C}$).

According to “Concentrative Properties of Aqueous Solutions: Density, Refractive Index, Freezing Point Depression, and Viscosity”, in CRC Handbook of Chemistry and Physics, 90th Edition (CD-ROM Version 2010), David R. Lide, ed., CRC Press/Taylor and Francis, Boca Raton, FL., the properties of a potassium bromide solution of with a mass fraction of $w_{\ce{KBr}} = 40.0\ \%$ at $T = 20\ \mathrm{^\circ C}$ are as follows.

• molality: $b_{\ce{KBr}} = 5.602\ \mathrm{mol\ kg^{-1}}$
• concentration: $c_{\ce{KBr}} = 4.620\ \mathrm{mol\ l^{-1}}$
• density: $\rho = 1.3746\ \mathrm{g\ cm^{-3}}$

It seems, that the discrepancy arises from the fact, that the mentioned density of $3.119\,\mathrm{g\,ml^{-1}}$ belongs to solid $\ce{KBr}$ (Source - Which might be wrong as well, since wiki suggests a much lower value of $2.74\,\mathrm{g\,ml^{-1}}$, which is in good accordance with the information available on the GESTIS Substance database: $2.75\,\mathrm{g\,ml^{-1}}$ at $20\,\mathrm{°C}$) rather than to a solution.

This is why your measured density and the literature density are not consistent.

I don't know where you got your information from, since you did not name any sources, but it was either wrong there, or it was mistaken with a solid density (or both). In his very informative answer, Loong already named some citations for densities of aqueous solutions.

Addendum: The source stating the $3.119\,\mathrm{g\,ml^{-1}}$ does not seem to be reliable at all, since it states a $\mathrm{mp}$ of $734\,\mathrm{°C}$ and a lower $\mathrm{bp}$ of only $58.8\,\mathrm{°C}$, which does not sum up at all.

• Amen. The same source says that KBr has a vapor pressure of 175 mmHg, which is absurdly high. The "synonyms" for KBr listed include BROMINE TS; BROMINE WATER; BROMINE LIQUID; BROMIDE BROMATE and many other absurdities. Potassium bromide is not the same as liquid bromine! Nor is it a bromate! – Curt F. Feb 23 '16 at 0:21
• My guess is that the density listed on the absurd site is the density for potassium bromate, not potassium bromide. The properties on that page are an absurd scramble of the properties for bromine, potassium bromate, and potassium bromide. None of them seem to apply to aqueous solutions. – Curt F. Feb 23 '16 at 0:22
• @CurtF. Thanks for the supplementation. Yeah, this site is a colossal cheek - Calling itself "Chemical Book" – lcnittl Feb 23 '16 at 8:18