I need Aqua Regia knowledge!!

[H2SO4]

I realized because im gonna be making HCl and nitric acid, why not make aqua regia too. Ive been researching this stuff and found that aqua regia is an extremely corrosive, fuming liquid. So ive found that you simply mix concentrated nitric and hydrochloric acid together in a 1 to 3 ratio. I can imagine if this came in contact with skin or eyes (beyond bad!)!!!!!!!!! Wat you get is a fuming brown liquid that can disolve gold. Can this be stored in a normal glass vessel with a stopper. And if/when i mix the acids, will there be an evolution of heat or a violent reaction that i should be aware of. I realy want to try this but i need to no more about aqua regia.

 

Trust me, around dangerous/corrosive/poisonous chemicals i am very safe and catious.

[collector]

1. The molar ratio HCl:HNO3 is 3:1.

But if you calculate on the concentrated acids, their molar konc etc, the VOLUME ratio between the commercially available acids will be 4:1 !

Remember that konc HCl is ~35%, and konc HNO3 is ~65%.

 

2. The acids react to form a water solution of nitrosyl chloride (NOCl) and chlorine. The originally colourless mixture is soon going yellow and dark orange red (by the NOCl), and emits an intense smell of chlorine.

 

Fume hood is needed, goggles and gloves too!!!

 

I did notice a tiny temperature rising during the reaction. The mixture can be stored for a short time in a glass bottle, but there is a risk that both the components will be gassing off above room temperature. And consequently pressure increase inside a closed bottle!

Should be stored for a short time only at low temp, unstable even in cold.

Aqua regia is most often used freshly prepared because of the decomposition.

 

I have spilled drops of this liquid on the skin, gives the same local burns as any strong acid. Wipe of immediately, rinse with plenty of water.

 

3. The violent reactions occur when the liquid come in contact with reducing agents/easily oxidizable substances.

Metals, even noble metals, are rapidly attacked, producing either soluble chlorocomplexes (Au gives (AuCl4)- in solution) or insoluble chlorides (Ag gives AgCl(s) ).

 

Some of the reactions are violent; once I tried reaction with Sb, and that was certainly violent!!

 

Other reactions may be slow (Pt reacts a lot slower than Au).

 

Only a few metals are not attacked by aqua regia, like Ir, Ru, Rh. Especially Ir withstand attacks from all acids even when finely divided.

 

When working with aqua regia, always use goggles, fume hood, and only small amounts (maximum ~10 ml). Should be freshly prepared.

[raivo]

Do you know how much aqua regia is needed to dissolve 1g of gold?

[MulderMan]

you just need enough to cover the gold, i just pipetted some over so it would cover. also its best to make it fresh every time, not to keep it.

[budullewraagh]

i think the most important thing you should know is that it is only to be mad in small quantities. personally, i suggest 5mL, mainly because you have never worked with it.

 

just a followup: HNO3 can be more than 65%; 70% is required for most nitrations. 85% is required for some.

[jdurg]

I used Aqua Regia all the time when I was working with GC/MS machines. It's VERY effective at cleaning the ceramic components of the machines when you have to take them apart and clean them. We never kept the Agua Regia stored. We'd make it in whatever quantity we needed it when we needed it. As soon as the two acids are mixed, you'll see the color of the solution change to yellow and the smell of chlorine gas immediately evolves from it. (Even with a fume hood at full blast). Remember that Agua Regia is so effective because it creates a mixture of three INCREDIBLY powerful oxidizers; NOCl, Nitric Acid, Chlorine Gas.

[akcapr]

Isnt there a strong acid that can be made with hcl and sulfuric or someting like that?

[akcapr]

I suggest sticking to oher acids. This one isnt that special from wat ive heard, except it can dissolve gold (who n the right mind will destroy gold instead of selling it. A chemist.. but thats beyond the point).

[collector]

For nitration purposes in organic chemistry "nitration acid" is often used, a mixture of HNO3 and H2SO4. In this mixture, the HNO3 actually acts like a base(!), producing nitryl cations, (NO2)+. This is the specie attacking organic molecules.

 

In this acid mixture, the sulfuric acid acts like a strong acid, even together with nitric acid.

[jdurg]

Nitration acid is something you want to never store and you should only make it as you need it. ANYTHING organic that comes in contact with it can be inadvertantly turned into a very unstable compound, or a compound that will decompose in a violent manner. Plus, when making it you are mixing very concentrated sulfuric and nitric acids, so the heat of dissolution of the sulfuric acid can make it unexpectedly boil. It's not something you want to play around with or spill on yourself. (I made nitroglycerin (VERY tiny amount. Maybe 1 mL or two) and nitrocellulose in college. I was more nervous about the nitration acid than I was the product!)

[MulderMan]

nitroglycerin shouldnt be too bad to make if made under the right conditions, ive never done it nor intend to but it looks pretty straight forward. whats so bad about nitrocellulose? ive never heard of it thats all.

[H2SO4]

nitrocellulose is just cotton soaked in an concentrated soulution of nitric and sulfuric acid. Its done in an ice bath i think. seems safer to make then nitroglycerin. Although nitroglycerin doesnt seem to insane to make, just as long as your careful and work with an ice bath and ,ale small amounts.

[akcapr]

nitro cotton or cellulose is just like a big matchhead but less intense

[budullewraagh]

"nitrocellulose is just cotton soaked in an concentrated soulution of nitric and sulfuric acid."

well, it's nitrated cellulose. you nitrate the cellulose using sulfuric and nitric acid. if you remove the acids, you have nitrocellulose

[jdurg]

The problem is, if you don't remove the acids it becomes very unstable and will spontaneously ignite, or go 'boom' if you have it confined. That's what makes nitration so dangerous. It's the actual cleaning that you MUST do which is so dangerous. With nitroglycerin, for example, ANY remaining acid in the stuff will make it frighteningly unstable. So you have to remove the acid through neutralization. The neutralization could generate enough heat or motion to make the nitroglycerin detonate. It's straightforward, but incredibly risky.

[budullewraagh]

out of curiosity, what would you use for neutralization?

[jdurg]

I have heard of people using either a moderately strong solution of sodium hydroxide, or powdered sodium bicarbonate. The NaOH would have to be done with the solution VERY cold as the dilution of the sulfuric acid and the neutralization will result in a lot of heat and a potential KABOOM. With sodium bicarbonate, you have to be careful that you don't add too much at once an cause a violent release of CO2 which could agitate the nitroglycerin too much and make it go KABOOM! With nitrocellulouse, the agitation really doesn't matter so soaking the nitrated cotton in a saturated NaHCO3 solution until the fizzing ceases is an effective way.

 

My senior year of high school I took an AP Chemistry course. Since the AP Exam happened before our final, the teacher made our final 'optional' but we could show up for the slotted time period if we wanted to for some extra credit. Since I had to be at school anyway, I decided to go. It was just me and a few other people there, and the teacher gave us almost full reign of the chemical supply cabinet to come up with an experiment. We could do anything we wanted as long as the materials were there in the chem lab. (Though things with alkali metals, white phosphorus, and halogens were out of the question. ) So when looking through the supply closet I saw the concentrated nitric acid and the concentrated sulfuric acid. I immediately thought 'nitroglycerin', but the teacher said no. heh. Then I suggested nitrocellulouse and she was a lot more willing to let us do that since it's far more stable, and doesn't really explode unless confined. The only problem is that we had no cotton.

 

Not even the first aid cabient had cotton swabs. So we had everything we needed except cotton, and since it was during the finals we couldn't leave the room in order to go to the nurse's office to get some cotton balls. I then thought about other sources of cotton, and realized that I was wearing a somewhat chemically 'eaten' tee-shirt that I could cut a piece off of. I ripped out the tag from the back, and it said 100% cotton. It was a white tee-shirt so I took some scissors and cut off a couple of nice sized pieces from the bottom. We then nitrated them. Nitrocellulouse burns REALLY fast once it's been neutralized and dried, and if it is confined it makes a pretty loud pop. I was able to see why it is called 'guncotton'.

[The Thing]

Nitric acid by itself is a powerful oxidizing agent, yet its chemical equilibrium for the reaction w/ gold only permits a miniscule amount of Au+3 cations to form. But in the "royal water", hydrogen chloride reacts with nitric acid, thus creating nitrosyl chloride (NOCl), water, and CHLORINE. The chlorine anions allow the formation of a stable ion, chloraurate complex (AuCl4-). Due to this high concentration of Cl- ions in aqua regia, the Au+3 reacts almost instantaneously, keeping its concentration low in the mixture, thus allowing more gold to be oxidized into Au+3, and the gold is dissolved.

[BenSon]

How is the Cl gas produced what do the Cl anions donate their electrons too?

 

~Scott

[budullewraagh]

i think the half reactions would be:

N+5+2e- --> N+3

2Cl- --> Cl2+2e-

 

so the overall reaction would be:

HNO3+3HCl-->NOCl+Cl2+2H2O

 

i like how nitric acid is a base

[jdurg]

The chloride ion from HCl is oxidized by the nitrate ion which results in the formation of chlorine gas. The nitrate ion is reduced at the same time into nitrite which is further reduced to NO+ which will bond with another free Cl- ion to form the NOCl. Meanwhile, the liberated oxide ions bind to the free hydrogen ions in the acidic solution, thus forming water.

[budullewraagh]

isnt that what i just said?

[jdurg]

But what I posted was in more common english. You kind of left out the oxygen there. ;-)

[budullewraagh]

well, i assumed people would find it to be an acid base reaction.

 

btw im STILL laughing at the fact that HNO3 is a base in this case

how poetic i am

[jdurg]

As Einstein once said, EVERYTHING is relative.