Talk:Aqua regia

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Contents 1 Gold Metal or Ion? 2 Copper doesn't dissolve? 3 Form of Gold in Solution 4 Color of aqua regia 5 disactivation of Acqya regia 6 precipitated the gold out of the acid?

[edit] Gold Metal or Ion?

The following phrase is a ambiguous: "which react with the gold to produce chloraurate anions." Is the article referring to the gold metal or the Au3+ ions produced by reacting with nitric acid? absolutecaliber

The sentence is accompanied by the relevant equations. The equation shows that the chloride ions react with the ionized gold (Au3+). The sentence is unambiguous if viewed in this overall context. Leeannedy 20:18, 1 November 2006 (UTC)

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If painters did use aqua regia to clean their brushes, the metal parts would dissolve and the organic parts would be burned. I think, if they did once use something called aqua regia, it must have been something different. Can you verify your info source? -- Marj Tiefert 09:13 Jul 21, 2002 (PDT)

Of course, they use it in a light solution (with water, I'd think) that allows to do it without damages. I believe that the substance keeps this name even if it is in a poor concentration. As for what I personally directly know, a close friend of mine was a reputed painter and I still remember the typical smell of aqua regia in his "studio", as well as the regular, unavoidable operation of cleaning the brushes in it at the end of the work. We call it "acquaragia", but my dictionary confirms me we should be talking about the same substance; if anyone here can tell the correct name of what painters do use for this purpose, I might check if we have a different translation and, consequently, if I just made a silly mistake (hope not! :-))). -- Gianfranco

Aqua Ragia is more commonly known as turpentine in English and is a completely different substance from Aqua Regia -- Derek Ross

Well, I made a silly mistake, we use the same "acquaragia" for both and I got lost in the middle. Sorry for the confusion... -- Gianfranco

Put that in the article! - Omegatron 22:41, Feb 4, 2005 (UTC)

According to [1], it would seem that the Nobel prize medals which were dissolved into aqua regia were, in fact, created from "fresh" gold rather than that dissolved into the solution.- Caspian 11:26, Oct 31, 2005 (EST)

It's not clear, but at the end of the article it says that Francke was given a "recoined" medal, which suggests that at least his was made from the same gold. KarlM 04:40, 25 July 2006 (UTC)

[edit] Copper doesn't dissolve?

I put a penny into some fresh aqua regia (Yellow and fuming). Nothing happened. Why doesn't the copper get oxidized as it does in HNO₃? —The preceding unsigned comment was added by 71.142.218.139 (talk • contribs).

While I highly doubt that you actually used aqua regia (if you have access to these sorts of chemicals, one would think you would know the answer), I'll try to humor you. First of all, the penny is not pure copper: it's an alloy of metals plated in copper. It's 97.5% zinc (courtesy of our very own Cent (United States coin) article). However, aqua regia should still be strong enough to dissolve zinc too. Check the dilutions: the acids you used probably weren't high enough concentration. However... IANAC (I am not a Chemist) — Ambush Commander^(Talk) 03:06, 26 February 2006 (UTC)

It's not that hard to find sulfuric and nitric acid. I purchased both off eBay and produced my own aqua regia. absolutecaliber

They both have to be at dangerous concentrations though. — Edward Z. Yang^(Talk) 02:20, 15 November 2006 (UTC)

absolutecaliber, Sulfuric Acid is not a component of aqua regia.

[edit] Form of Gold in Solution

Each of the referenced external links indicates that the dissolved form of the gold is the anion chloraurate (AuCl₄^-) rather than the acid form chlorauric acid (HAuCl₄). In which form is the dissolved species of the gold? I assume that in reality an equilibrium is present between the chloraurate and chlorauric acid. In this manner, the dominant species would depend on the acid dissociation constant of chlorauric acid and the concentration of hydronium ions. Since the oxidation reaction generates water, the hydronium concentration will vary with the quantity of gold dissolved. Can someone shed some light on the typical dominant form? If the dominant form is the chloraurate anion, I believe the reactions should be changed to reflect this (since they are written in ionic form). Leeannedy 12:25, 11 March 2006 (UTC)

[edit] Color of aqua regia

I was once a chemical techician in a semiconductor plant, and I used to wash quartz-glass ampules in aqua regia before they were used in a diffusion oven. I don't know why Columbia Encyclopedia would say it is yellow. It is only yellow for a little while. When you first mix the HCl and the HNO3 it is clear. Within a minute or so it starts turning yellow, but goes from there to orange and finally a deep red, like boiling, fuming cherry Kool-Aid. It is an amazing thing to behold. Scary, but you learn to be very careful when you're up to your elbows in that stuff under a fume hood. If you're going to pick one color for it, you'd definitely pick red if you ever worked with it. 128.244.230.13 21:26, 19 April 2006 (UTC)Richard Waddel

1Aug06RLC I made up a solution for semiconductor use and the color is pink or red with bubbles. Semiconductor solution is different than standard Aqua Regia mixture. The mixture difference may cause different solution color. Semiconductor Mix HNO3:HCl (2:1) , Standard Mix HNO3:HCL (1:4)

I've reverted it, because most other sources on the web say it's yellow. I understand that your personal experience may tell you otherwise, so if you can find a reputable source, we should make note of the color changes in the article. — Edward Z. Yang^(Talk) 00:36, 20 April 2006 (UTC)

Ah, this source says it's red, yellow or gold. Will reword accordingly. (you're right). — Edward Z. Yang^(Talk) 00:38, 20 April 2006 (UTC)

For metal etching such as in swords, the solution should be aged for a month, I don't know why. This may account for different color observations.

[edit] disactivation of Acqya regia

Hi every body, I need to know if it is possibile, and if yes, how to disactive Acqua regia in yor lab? If any one knows, please send me your information best regards Nabil

The same way you neutralize any other acid. (seriously though, I am not a chemist and if you have Aqua Regia but don't know how to disable it, you probably shouldn't be either.) Please direct non-article related questions to the help desk. — Edward Z. Yang^(Talk) 19:06, 21 August 2006 (UTC)

[edit] precipitated the gold out of the acid?

How would this be possible? —The preceding unsigned comment was added by Archangel991 (talk • contribs) .

Since gold is such an unreactive metal, dissolving it is the hard part. Getting it back into metal form is easy. Just add any weak reducing agent. This website says: "The gold can then be selectively precipitated using a number of reducing agents, such as ferrous sulphate (also known as Copperas), sodium bisulphite, and sulphur dioxide gas. Other less frequently used agents include hydrazine, formaldehyde, oxalic acid, and hydroquinone." —Keenan Pepper 00:03, 2 September 2006 (UTC)