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Here it writes that nitrohydrochloric acid (possibly Aqua Regia) is of the ratio of $18:82$, which is $1:4.56$ in a simpler form. On Wikipedia and every other source i found the ratio $1:3$. So what's the truth behind this?

Also is Aqua Regis a valid way to call the mixture? On Wiktionary it says that this is a synomym of Aqua Regia but why would it have such a different ratio then?

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    $\begingroup$ Having made aqua regia fairly regularly during my (short) time in the lab - I never measured it out precisely, and I don't think the exact ratio matters too much... You get a slightly different colour (more nitric acid = more brown), and the exact composition won't be the same, but it'll probably still dissolve what you throw in it. BTW, 18:82 in what units -- volume, mass, etc.? 1:3 refers to the stoichiometry. $\endgroup$
    – orthocresol
    Nov 30 '20 at 16:14
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    $\begingroup$ "Aqua regia" is "royal water", or more literally "water of kings". "Aqua regis" is "water of the king". I would suspect the latter has occurred because people didn't know Latin, or translated the term from their own language back into Latin. (For example, in German it's "Königswasser" which means literally "king's water", though it could also be interpreted as "water of the king" or even "king water"; hence also similar terms in languages spoken around the Baltic Sea and in Scandinavia, where German cultural influence was significant for many centuries.) $\endgroup$
    – tripleee
    Nov 30 '20 at 16:24
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    $\begingroup$ @tripleee, Interesting account. You are right. I checked the etymology it was indeed aqua regis until 1612s and by 1650s aqua regia appeared. $\endgroup$
    – M. Farooq
    Nov 30 '20 at 16:53
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    $\begingroup$ It is called the Unabridged Oxford English Dictionary (www.oed.com). I think it is 22 volumes in print if I remember correctly. Unfortunately, it is not free and you have to pay for subscription or a library has a license. The ordinary OED does not have dates with usage examples. $\endgroup$
    – M. Farooq
    Nov 30 '20 at 21:45
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    $\begingroup$ Aqua regia does not have that rigid fixed composition as the OP is suggesting. There is no magic in his 18:82 numbers. $\endgroup$
    – M. Farooq
    Nov 30 '20 at 22:16

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