The silver halides $\ce{AgCl},~\ce{AgBr},~\ce{AgI}$ are insoluble in $\ce{HNO3}$. This is given in J.D.Lee's inorganic chemistry text. (The strength of nitric acid is not specified though).

But won't this reaction take place? $$\ce{X- + HNO3 -> X2}$$

This example is taken from JD Lee's book itself: $$\ce{6Br- + 8HNO3 -> 3Br2 + 2NO + 6NO3- + 4H2O}$$

because concentrated Nitric acid is a powerful oxidizing agent.

  • 3
    $\begingroup$ What kind of reaction is that ? It's not balanced either in elements or in charges. $\endgroup$ Mar 21, 2016 at 16:48
  • $\begingroup$ @Hippalectryon its a basic oxidation reaction. $\endgroup$
    – Aditya Dev
    Mar 21, 2016 at 16:53
  • $\begingroup$ Not all silver halides are insoluble in water. AgF is highly soluble in water. $\endgroup$
    – user124978
    Jun 16, 2022 at 19:52
  • $\begingroup$ Nobody is interested in the behavior of $\ce{AgF}$. Only $\ce{AgCl, AgBr, AgI}$ are studied and discussed. $\endgroup$
    – Maurice
    Jun 16, 2022 at 20:39

2 Answers 2


Nitric acid (even concentrated) is essentially an aqeuous solution.

Effectively, silver halides will not dissolve in water (they have incredibly low $K_\text{sp}$), so the reaction indicated is moot.... there is no appreciable concentration of bromide in solution to be oxidized.

$K_\text{sp}(\ce{AgBr}) = 5.0\times10^{-13} \Rightarrow [\ce{Br-}] \approx 700~\text{nM}$

  • $\begingroup$ Low but not incredible, Bi2S3 is almost incredible but even that is attacked by concentrated nitric acid [I think I have never tried it] All this seems to be a simple experiment for a high school lab [with good attention to safety]. Concentrated nitric is far from an aqueous solution. I have a friend who is in pain her whole life from a lab accident involving concentrated nitric acid. $\endgroup$
    – jimchmst
    Jun 16, 2022 at 21:42

The diagnostic test for Cl-, Br- and I- is reaction with Ag+ in a dilute nitric acid solution. The reason for the nitric acid is not because the silver halides are not attacked by nitric but that the dilute acid solution prevents the formation of other insoluble silver salts such as silver oxide, carbonate, phosphate, cyanide [careful here] and who knows what else. You cannot use sulfuric [perchloric will work but why even have it around] and acetic might work. Nitric is perfect. I have little doubt that the silver halides would be oxidized to the halogens or even higher oxidation states by hot concentrated nitric acid. You are welcome to try the next time you are in the lab.


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