ammonium hydroxide and aluminium

[the guy]

does ammonium hydroxide react with aluminium? what are the products? what is the equation?

[John Cuthber]

Last time I checked, ammonium hydroxide didn't exist.

[the guy]

uh, yes it does, i have some on me right now

 

its also known as ammonia water, ammonical liquor, ammonia liquor, aqua ammonia or aqueous ammonia

 

any of those ring a bell?

[Justonium]

The ammonium hydroxide is a catalyst. The aluminum reacts with the water VERY SLOWLY to form aluminum hydroxide and hydrogen gas. The speed at which it occurs is just ridiculously slow. There are no visible effects on the aluminum for weeks, we're talking YEARS. I've hooked it up in an indirect reaction to harvest electrical current, and though you get almost a volt, the current is in micro amps.

[John Cuthber]

uh, yes it does, i have some on me right now

 

its also known as ammonia water, ammonical liquor, ammonia liquor, aqua ammonia or aqueous ammonia

 

any of those ring a bell?

 

They all ring a bell.

Ammonium hydroxide still doesn't exist.

Measure the elctrical conductivity of the stuff and you find it's a bit short on ions. If you look at the raman spectrum you find there's nothing new covalent there either.

[hermanntrude]

John, you're being a bit of a pedant. While it's true that ammonium hydroxide has never been isolated, most aqueous solutions of ammonia are still sold under the name of ammonium hydroxide. It's annoying, but true.

 

So perhaps if we re-word the question "does ammonia in water, which is usually called ammonium hydroxide despite the fact it doesn't actually form ammonium hydroxide, react with aluminum?", then you'll answer the poor fellow's question?

[the guy]

haha lol ok i see now that there is actually no such thing as ammonium hydroxide but thank you to justonium for answering, john cuthber for enlightening me and hermanntrude for putting it so well:-)

[rohit_2787]

Hey guys m thinking of using aluminum in an ammonia/water solution heat exchanger. Would it be a problem. Is there any specific grade of aluminum alloys which i can use to prevent corrosion if it occurs.

[Santalum]

Last time I checked, ammonium hydroxide didn't exist.

 

How do you figure that John:

 

Basicity of ammonia in waterIn aqueous solution, ammonia deprotonates a small fraction of the water to give ammonium and hydroxide according to the following equilibrium:

 

NH₃ + H₂O NH₄⁺ + OH⁻.In a 1M ammonia solution, about 0.42% of the ammonia is converted to ammonium, equivalent to a pH of 11.63. The base ionization constant is

 

K_b = [NH₄⁺][OH^-]/[NH₃] = 1.8×10⁻⁵

 

It can't exist as a solid of course but it does exist in aqueous form.

 

The ammonium hydroxide is a catalyst. The aluminum reacts with the water VERY SLOWLY to form aluminum hydroxide and hydrogen gas. The speed at which it occurs is just ridiculously slow. There are no visible effects on the aluminum for weeks, we're talking YEARS. I've hooked it up in an indirect reaction to harvest electrical current, and though you get almost a volt, the current is in micro amps.

 

 

Works much better with sodium hydroxide.

[John Cuthber]

How do you figure that John:

 

In exactly the way which I stated earlier.

"Ammonium hydroxide still doesn't exist.

Measure the elctrical conductivity of the stuff and you find it's a bit short on ions. If you look at the raman spectrum you find there's nothing new covalent there either."

 

Did you not see it, or did you not understand it?

[Santalum]

Measure the elctrical conductivity of the stuff and you find it's a bit short on ions."

 

Did you not see it, or did you not understand it?

 

Short of ions not devoid of them, which means it has some electical conductivity albeit low but higher than pure water.

 

How do you explain the basicity/presence of hydroxide ions?

 

Is you argument something along these lines John:

it stinks, and there "is no such thing as ammonium hydroxide" !

 

There is ammonium

There is hydroxide

 

 

If so then I could also argue that, in aqueous solution, there is no such thing as sodium chloride. There is however sodium+ and chloride-.

Edited March 3, 2012 by Santalum

[John Cuthber]

Ammonia is a base- it's the lone pair that does it. What's to explain?

 

A solution marketed as, say 50% ammonium hydroxide is about a thousand times less concentrated than the claim. That's wrong enough to count as practically non existent.

Also, ammonium ions are present and hydroxide ions are present (albeit damnably few of them) but there's no compound present that you could sensibly call ammonium hydroxide.

Edited March 3, 2012 by John Cuthber

[Suxamethonium]

If you dissolve ammonia in water, you will get some hydroxide ions. The counter ions will be ammonium ions. It may not be much, but it is still present enough to be concluded that ammonium hydroxide is a (marginal) component of the solution- just because the equilibrium lies hard in favour of the molecular species doesn't mean the ions cannot exist at all. I don't see any reasonable way that can be denied without grossly changing acid/base (or even lewis) theories. If you can show ^-OH can magically exist on its own in such a case I will gladly eat my words.

[John Cuthber]

The ions exist, undoubtedly.

It's the compound that I have yet to hear any evidence for.

[Santalum]

The ions exist, undoubtedly.

It's the compound that I have yet to hear any evidence for.

What does that mean exactly?

 

Are you saying that because it can't exist as a crystalline salt ammonium hydroxide (as an ionic compound) therefore does not exist at all?

 

I have my doubts that many of your fellow chemists would agree with such a conclusion.

Edited March 5, 2012 by Santalum

[Mr.Chemist]

From what the product of 'theoretical ammonium hydroxide' and aluminum are, to the debate whether ammonium hydroxide exists or not. Haha. It's actually not with the name. It is the reaction of ammonia and water that there is a production of ammonium ion and hydroxide ion (though some part of the hydroxide ion production is due to ionization of water itself). OF course both ions exist but as I have said it is not with the name. There is no such evidence that ammonium ion clings to the hydroxide ion. They coexist in solution. In the question whether what would be the product, I haven't tried putting aluminum to ammonia solution. But most probably, aluminum hydroxide will be produced (I just don't know if it would really take years).

[Suxamethonium]

First of all to address John. "Ammonium hydroxide" is employed as a trivial name so arguing that it is not an isolated compound for the point of making a snide remark is fairly juvenile. Also, here- it is called "ammonium hydroxide solution" anyway so your argument doesn't even hold true in such situations.

 

As for ammonia and aluminium, I have no specific idea- but the presence of hydroxide may account for silimilar reactions as NaOH. If this is true, I don't think I would agree with it being a catalytic reaction (not unless the hydroxide is replaced). It is possible you might produce an ammonium/aluminium complex? So I don't know if you would yeild aluminium hydroxide anyway (note that reaction with NaOH gives sodium aluminate not aluminium hydroxide- maybe a similar reaction occurs (although more slowly)?).

[Mr.Chemist]

hahaha

[Slapgravel]

Just to add to this.....currently in the lab trying to reduce the solvent content of a litre of solution made to pH 10 with ammonium hydroxide solution. During evaporation some Al foil hit by the gas turned an nice black colour and smelt nicely of NH3. No time or reason to analyse it but while looking for the reaction I found this forum.....hope it helps in any kind of small way.

 

Also John...if something is labeled 'Nujol' then one can refer to it as Nujol...if something is labeled as 'Borax' one can refer to it as Borax. This solution is labeled 'Ammonium Hydroxide Solution' hence that is how I shall refer to it. If op had said 'I mixed ethylene with...' would you have said 'Ethylene doesn't exist!! I know only of Ethene!!' of course not. Stop being a tool.

[John Cuthber]

Nujol is a perfectly good name for the stuff it represents. So is ethylene.

On the other hand ammonium hydroxide is outrightly misleading.

A bottle labelled as 50% ammonium hydroxide contains the ions equivalent to about 0.05% ammonium hydroxide.

Would you be happy with that in any other context?

 

It's not that it isn't isolated that's the problem. The issue is that it's about 99.9% not there.

 

I'm perfectly happy with the outdated names but I'm sure you agree that they are not helpful except to a historian.

Salts of lemon is pretty unhelpful (never having been near the yellow citrus fruit) and, in much the same way, killed spirits was never really alive.

Thankfully the preparation of "oil of Dutch chemists" doesn't involve alchemists from the Netherlands any more that advocaat is made from lawyers.

 

We have ditched most of the silly names- why keep this one?

It also seems odd to say "Also, here- it is called "ammonium hydroxide solution" anyway "

It was indeed called that in your post- but not in the original one to which I was responding, and I don't do time travel

 

" It is possible you might produce an ammonium/aluminium complex? "

I'm not saying it's impossible, but a complex between two positively charged ions would seem unusual.

 

 

And it's just as well that tools are, by definition, useful or someone might interpret "Stop being a tool. " as an ad hom which would be particularly unfortunate in a first post.

[hypervalent_iodine]

!

Moderator Note

Slapgravel, please observe our rules regarding civility and courteousness when posting. Calling someone a 'tool' is not an advisable course of action, nor does it add to your argument.

 

[Suxamethonium]

"I'm sure you agree that..."

I don't see how you can be sure of that. If you are actively listening then you will notice we are outrightly saying why we DON'T agree that such names are not useful- in fact due to familiarity these names are probably MORE useful.

 

"ammonium/aluminium complex"

sorry, I wasn't very clear- I meant things similar to ammonium/aluminium double salt complexes (like ammonium aluminium sulfate)- although the ammonium is not truely part of the complex.

 

"We have ditched most of the silly names- why keep this one?"

Well it is not particularly "silly". In theory the name makes sense- it's just in that in practice the equilibrium isn't favourable. Most people (particularly those without a chemistry background) can identify with the term "ammonium hydroxide" so why change it just for the sake of being anal? Also- whilst the term inaccurately describes it's physical composition- it still accurately describes its properties and conveys its identity (I.e. High pH, reacts with acids to form ammonium slats) unlike your "salts of lemon" example which describes only the origin of the compound- not identity, properties or composition.

 

If someone refers to methylated spirits in a post are you going to jump on them with "Actually, methanol isn't added to ethanol cleaning products anymore- you need to call it denatured ethanol."? That is really not a helpful or constructive response and isn't that the point of this forum.. to be helpful not condescending?

 

Edit: Just an add. Ethylene (which you said was perfectly acceptable) can refer to H₂C=CH₂ or RCH₂-CH₂R. Obviously my point here is that in writing they are both written "CH₂CH₂" but structually and chemically they are completely different and without context is completely ambiguous. In retrospect "ammonium hydroxide" is actually more appropriate than the ethylene example because it doesn't require context for a person to know what you are refering to.

Edited March 23, 2012 by Suxamethonium

[John Cuthber]

"unlike your "salts of lemon" example which describes only the origin of the compound"

Nope, the point I was making is that salts of lemon isn't, and never was, made from lemons.

It's a hopelessly inaccurate name.

I grant you that ammonium hydroxide is only about 99.9% wrong but I think that's bad enough to ditch it.

 

"If someone refers to methylated spirits in a post are you going to jump on them with "Actually, methanol isn't added to ethanol cleaning products anymore- you need to call it denatured ethanol."? "

No, because, it may be anachronistic, but it's not wrong (in particular, some still does have methanol in and, short of analysing it, I wouldn't know).

On the other hand, if they said "I'm going to distil some methylated spirits to get methanol" I would warn them that they might be on a wild goose chase.

 

The distinction I am making is not between "IUPAC approved" and "archaic" but between "reasonably correct" and "hopelessly inaccurate, if not misleading."

[Suxamethonium]

"but I think that's bad enough to ditch it."

 

So you have the opinion that the term should be ditched- why do you feel that the rest of the chemist community has to agree with you? It's physically inaccurate, but so what? Why do you feel the need arrises to shut down a person asking a legitimate question for a nonlegitimate reason? There is really no reason why your first post was necessary- you didn't contribute to the question at all and in my opinion you were quite rude about it- particularly seeing as the term is widely accepted regardless of its physical accuracy. Maybe if the question related more specifically to the physcial state of the ammonia/ammonium in particular and was presented in an informative (not condescending) way I could see your point- but it sounds like you just want to be seen as "more correct" despite that many of us also understand the concept and physical availability of an ammonia/ammonium hydroxide solution.

[John Cuthber]

So, you do accept that the term is essentially wrong but you think we should keep it.

Because of that you think my attempt to send it on its way to oblivion was unnecessary.

If ammonia solution was actually ammonium hydroxide then it would dissolve aluminium just like sodium hydroxide does.

The reason there is a difference in reactivity is that ammonium hydroxide doesn't exist.

 

That does lead to an answer to the original question.

Logically, something that does not exist does not attack aluminium.

 

I grant that I could have been clearer and perhaps more polite- but I did answer the question.

You seem to have been to busy complaining about my post to realise that.

 

Incidentally, on this side of the pond, the term seems to be quite rare.

Edited March 24, 2012 by John Cuthber