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Author: Subject: What is my best bet at diggesting a mix of all elements that can form acetates at once, as I would do with nitric acid?
VeritasC&E
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[*] posted on 24-7-2022 at 19:22
What is my best bet at diggesting a mix of all elements that can form acetates at once, as I would do with nitric acid?


Nitric acid and acetic acid have this in common that they both form at least somewhat soluble salts (with very few exceptions).

Based on this I would like to substitute nitric acid for acetic acid in order to dissolve a mix of all elements that can form acetates all at once (this can be useful to perform a very fine analysis of complex metal alloy composition, for instance, or to perform trace metal analysis).

Now as much as both acids generally form at least somewhat soluble salts, they have a lot of differences. Nitric acid is a much stronger acid, it is an oxidizer, and (as far as I know) it almost fully dissociates in solution.

I'm prepared for longer digestion times (I'm ready for up to a few days if necessary, preferrably less than two), but I'm wondering what my best bet could possibly be at digesting all different elements that form acetates at once (alltogether mixed)?

I'll probably digest this under reflux a dozen degree under the BP of acetic acid.

Should I add a bit of H2O2 before starting the digestion? I know peracetic acid is a powerful (and also somewhat unstable) oxidiser. Would this universally help or at least be neutral to the formation of the corresponsing acetate salt of all elements that form acetates?

Would it help to mix in a tiny amount of another acid that would serve as intermediate in the digestion into acetates of some elements (a bit like two acids work together in aqua regia)?
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[*] posted on 25-7-2022 at 00:13


Aqua regia is not really just a mix of acids, nitrosyl chloride is formed which does the oxidation.

I think you might be able to oxidize the metals with a mix of H2O2 and acetic acid if they normally oxidize in HNO3 alone, but you will need at least an equimolar amount of H2O2, unless the metals are really reactive off course. There might be some exception metals that don't get oxidized though and many metals catalyze the decomposition of H2O2.
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[*] posted on 25-7-2022 at 01:01


Quote: Originally posted by Tsjerk  
Aqua regia is not really just a mix of acids, nitrosyl chloride is formed which does the oxidation.

I think you might be able to oxidize the metals with a mix of H2O2 and acetic acid if they normally oxidize in HNO3 alone, but you will need at least an equimolar amount of H2O2, unless the metals are really reactive off course. There might be some exception metals that don't get oxidized though and many metals catalyze the decomposition of H2O2.


Will it dissolve everything that forms acetates with gradual additon of eventually equimolar quantities of H2O2?

Maybe I can save some H2O2 by simply slowly bubbling O2 into the mixture as a first step (maybe even air but I fear the formation of very insoluble carbonates could interfere with the digestion of some elements into their acetate salt / at least on a reasonable time scale).
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[*] posted on 25-7-2022 at 12:53


Lots of things destroy peroxide catalytically.

Mixtures of acetic acid with oxidants are potentially explosive so be very careful about that.
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[*] posted on 25-7-2022 at 13:08


If you use aqueous solutions of acetic acid and add some H2O2 to that, then the risk of explosion is minimal. I would not worry about that too much. Catalytic decomposition of H2O2 by metal ions, however, is a thing which may happen with many metals.

Also be prepared to accept very slow reactions. Quite a few metals do dissolve in aqueous H2O2/acetic acid mixes, but it will take time. Acetic acid is a weak acid and using very concentrated acid hardly helps, because it makes dissolving of formed salts more difficult. I would go for a concentration of 10%, maybe 15% of acetic acid and 5% or so of H2O2.

With acetic acid alone, the reaction will be even slower. Days, or weeks.




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[*] posted on 25-7-2022 at 17:42


People need to stop saying "I will substitute X for Y" if they don't know how the phrase works. Substituting nitric acid for acetic acid means you would be using nitric acid for this procedure, which is not the case. This is driving me crazy so now you get to be driven crazy.

What on earth are you attempting here? Do you have a fine powder of various metals mixed together? An alloy? Multiple alloys? You could benefit a lot more by clearly stating what you're trying to accomplish and what material you are digesting.
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[*] posted on 25-7-2022 at 22:38


To address catalytic decomposition, it may help to use a warm, stirred solution of acetic acid with H2O2 added continuously.



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[*] posted on 25-7-2022 at 22:41


Quote: Originally posted by VeritasC&E  

Will it dissolve everything that forms acetates with gradual additon of eventually equimolar quantities of H2O2?


Most likely not, but the question is: do you need to be able to dissolve everything?



[Edited on 26-7-2022 by Tsjerk]
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[*] posted on 26-7-2022 at 02:11


Quote: Originally posted by unionised  
Lots of things destroy peroxide catalytically.

Mixtures of acetic acid with oxidants are potentially explosive so be very careful about that.


Thank you for the warning, it is always better to be too much cautious than too little. If you read what I write right above your response, you'll see that I talk about "gradual addition" of H2O2, which will limit catalytic loss of H2O2 and peroxide accumulation.
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[*] posted on 26-7-2022 at 02:50


Quote: Originally posted by woelen  
If you use aqueous solutions of acetic acid and add some H2O2 to that, then the risk of explosion is minimal. I would not worry about that too much. Catalytic decomposition of H2O2 by metal ions, however, is a thing which may happen with many metals.

Also be prepared to accept very slow reactions. Quite a few metals do dissolve in aqueous H2O2/acetic acid mixes, but it will take time. Acetic acid is a weak acid and using very concentrated acid hardly helps, because it makes dissolving of formed salts more difficult. I would go for a concentration of 10%, maybe 15% of acetic acid and 5% or so of H2O2.

With acetic acid alone, the reaction will be even slower. Days, or weeks.


Thanks for the tip! I did have in mind to keep enough water as solvent in there looking at the fairly poor solubilities of acetates in acetic acid, but I was still going for a much higher concentration of acetic acid because of its poor dissociation (I was thinking of starting with 90% acetic acid). I'll adjust downwards after your input. I think I will do as follows that I'll start with 50% acetic acid and logarithmically dilute it down towards 15% acetic as the reaction proceeds and the solution saturates. I'd like to try a first phase with only very slow O2 bubbling (alone), and only when I see things don't proceed further then gradually add H2O2 sln over time, which will provide quite a great deal of dilution water on its own.

What do you think about the effect of having one percent or so of HCl in solution? Though I don't fully understand all the different dynamics involved, my initial intuition was that it could speed things up / facilitate digestion (as can be read in my first post). I then read a post yesterday about the reaction of copper metal with acetic acid which seemed to go in the same direction: in that post it is stated that the reaction between acetic acid and copper metal, in contact with air, wouldn't proceed at all (as can be expected by the low reactivity of copper), but this was changed with the simple addition of NaCl in solution; the same was attempted with another sodium salt but yielded no noticeable effect at all. So it's possible that it was all due only to the presence of the chloride ion in solution (it would be in any case interesting to see if there's some difference between HCl and NaCl; it can't be excluded that the formation of some of the many complex sodium containing salts, in the presence of chloride, play a role in bringing some of the less reactive elements into solution). The only big negative side I can see so far is that there are many more insoluble chloride species than there are insoluble acetate species (so depending on the elements present, the presence of HCl in solution, though initially speeding things up, may interfere with ultimately reaching complete dissolution).

[Edited on 26-7-2022 by VeritasC&E]
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[*] posted on 26-7-2022 at 03:48


Quote: Originally posted by Amos  
People need to stop saying "I will substitute X for Y" if they don't know how the phrase works. Substituting nitric acid for acetic acid means you would be using nitric acid for this procedure, which is not the case. This is driving me crazy so now you get to be driven crazy.

What on earth are you attempting here? Do you have a fine powder of various metals mixed together? An alloy? Multiple alloys? You could benefit a lot more by clearly stating what you're trying to accomplish and what material you are digesting.


Thank you for teaching me proper English. I looked it up and you are right, I must have picked it up from reading it being used this way on many instances. I don't have the option anymore to edit my original post however.

Do keep in mind that, as is my case, many members of the forum have English as a second or third language. It might be linguistically humbling to ask yourself how proficient people amongst your own social/private circle are, on average, in their second a third language compared to the general English proficiency denoted amongst us. This applies to yourself: I know nothing about you except that you are a chemist (at least at heart, as is my own case). How proficient are you then in German, the historical language of Chemistry?

By searching the web for the mistake you rightly pointed out, I had the occasion to read that the very dictionaries of English aren't all having this straight either. I would in general encourage you to reflect on you being deranged by a linguistic mistake in others (at all; but more especially so when the very linguists of that language aren't themselves getting it right). Not that helping others refine their language isn't good, and I am thankful for it, and I encourage you to do it again and again with a slightly improved approach; but it needn't emotionally affect you so.

As for what I would like to do, I think this was already described in my post:

Quote: Originally posted by Amos  
I would like to substitute [acetic acid for nitric acid] [*duly corrected] in order to dissolve a mix of all elements that can form acetates all at once (this can be useful to perform a very fine analysis of complex metal alloy composition, for instance, or to perform trace metal analysis).


So yes, alloys included, mixes of alloys too if you want. Powder, or clumps, crystals or minerals, chips or shots, flakes or turnings, ingots or pellets, anything you want. It can also be bio material that would then be burned down to minerals prior to dissolution.
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[*] posted on 26-7-2022 at 03:53


Quote: Originally posted by Tsjerk  
Quote: Originally posted by VeritasC&E  

Will it dissolve everything that forms acetates with gradual additon of eventually equimolar quantities of H2O2?


Most likely not, but the question is: do you need to be able to dissolve everything?

[Edited on 26-7-2022 by Tsjerk]


Quote: Originally posted by VeritasC&E  

So yes, alloys included, mixes of alloys too if you want. Powder, or clumps, crystals or minerals, chips or shots, flakes or turnings, ingots or pellets, anything you want. It can also be bio material that would then be burned down to minerals prior to dissolution.


If that is your question; definitely not. You just went from just metals to "all metals and minerals"...
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[*] posted on 26-7-2022 at 03:57


Quote: Originally posted by clearly_not_atara  
To address catalytic decomposition, it may help to use a warm, stirred solution of acetic acid with H2O2 added continuously.


These are two very good points which were covered in previous messages.

Quote: Originally posted by VeritasC&E  

under reflux a dozen degree under the BP of acetic acid


Quote: Originally posted by VeritasC&E  

gradual additon of eventually equimolar quantities of H2O2

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[*] posted on 26-7-2022 at 04:00


Quote: Originally posted by Tsjerk  
Quote: Originally posted by Tsjerk  
Quote: Originally posted by VeritasC&E  

Will it dissolve everything that forms acetates with gradual additon of eventually equimolar quantities of H2O2?


Most likely not, but the question is: do you need to be able to dissolve everything?

[Edited on 26-7-2022 by Tsjerk]


Quote: Originally posted by VeritasC&E  

So yes, alloys included, mixes of alloys too if you want. Powder, or clumps, crystals or minerals, chips or shots, flakes or turnings, ingots or pellets, anything you want. It can also be bio material that would then be burned down to minerals prior to dissolution.


If that is your question; definitely not. You just went from just metals to "all metals and minerals"...


ok, I got a bit carried away: consider just metals / alloys.

And to your question: yes, for trace metal analysis (clearly cited in my original post), all the different metals need to be pulled into solution.

[Edited on 26-7-2022 by VeritasC&E]
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[*] posted on 26-7-2022 at 05:04



Would CO2 be scrubbed efficiently by passing air in a bubbling stone through a 5% NaOH sln at room temperature before it being bubbled into the reactor? (I'm struggling to know if the short term solubility of CO2 in water, favoured by lower temperatures, but in general fairly slow, is of any relevance in comparison to the speedy reaction with NaOH)

Though bubbling air through the digestive sln this way may be a bit slower than systematically starting right off with H2O2 from the very beginning, I have a feeling that in some (/many?) cases it may save a lot of H2O2 to do so for the first phase of the digestion.
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[*] posted on 26-7-2022 at 05:10



I guess a colder CO2 scrubbing solution may be better. CO2 needs to dissolve before it reacts anyways, and that's also the culprit for scrubbing it. Now I don't know, but my uneducated guess is that even close to zero NaOH reacts faster with CO2 than the solution could saturate in it. Is this a good reasoning?
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[*] posted on 26-7-2022 at 12:16


I'm very sorry for my and everyone's inability to read your posts exactly as you intended them.

Besides that, there is not a single compound, solution or mixture in the world that can dissolve all metals, and acetic and H2O2 definitely can't. But what are you expecting? HNO3 also doesn't dissolve everything.

[Edited on 26-7-2022 by Tsjerk]
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[*] posted on 26-7-2022 at 12:51


Quote: Originally posted by Tsjerk  
I'm very sorry for my and everyone's inability to read your posts exactly as you intended them.

Besides that, there is not a single compound, solution or mixture in the world that can dissolve all metals, and acetic and H2O2 definitely can't. But what are you expecting? HNO3 also doesn't dissolve everything.

[Edited on 26-7-2022 by Tsjerk]


Your first sentence appears to me like a form of passive agression intended (subconsciously perhaps?) to feed animosity / polarisation in the thread. It´s just my perception; but in any case I would much like us to stay focused on science, and us to all keep contributing to the topic at hand. Would you agree to do that?

I apologise if I myself made any mistakes in that direction.

I just want us all to contribute towards finding out the best way and conditions to be able to convert into their acetate salt, within a single evolutive medium, as wide a range of different metals as can be done into nitrates in a nitric acid solution, within a reasonable, albeit longer, amount of time.

I believe there is a lot of utility to that for many reasons, including the following:
- Nitric acid is gradually getting banned across the used-to-be free world and is getting unavailable to most of us
- Acetic acid solutions can easily be made anywhere, and has been produced and used by humans for over ten thousand years.
- Acetic acid production has, in equimolar amounts, a lower carbon footprint than nitric acid production (for anyone who cares about such issues, which is not necessarily my personal highest priority to be fully transparent)
- Acetic acid is much safer to use, purify, and recycle than nitric acid.
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[*] posted on 26-7-2022 at 14:06


From reading all of the above posts in this thread, and going to nit-pick about the starting material, I've had a stream of conscious thought considering how I might handle this problem. If I were starting with a metallic/crystalline/amorphous inorganic sample of known origin, as an ancient chemist just past the age of alchemy and long before instrumental analyses were readily available, I would probably begin by consulting an inorganic qualitative analysis text for beginning methods to characterize the sample and to prepare a solution for(a) the usual scheme to identify cations; (b) the usual scheme to identify anions.

If course, nowadays I guess you would prepare a solution by chemically blasting it to near oblivion and then analyzing for metals by atomic absorption spectrometry and/or mass spectrometry.

Would I be guessing correctly that most home chemists would benefit from employing classical wet methods of qualitative and quantitative analytical chemistry? With one of today's inexpensive balances and a 1–10-gram sample size and with readily available glassware for volumetric and gravimetric analyses you can achieve precision to 4 or 5 digits.

Just the musings of an old fart...
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[*] posted on 26-7-2022 at 14:42


Quote: Originally posted by CharlieA  
From reading all of the above posts in this thread, and going to nit-pick about the starting material, I've had a stream of conscious thought considering how I might handle this problem. If I were starting with a metallic/crystalline/amorphous inorganic sample of known origin, as an ancient chemist just past the age of alchemy and long before instrumental analyses were readily available, I would probably begin by consulting an inorganic qualitative analysis text for beginning methods to characterize the sample and to prepare a solution for(a) the usual scheme to identify cations; (b) the usual scheme to identify anions.

If course, nowadays I guess you would prepare a solution by chemically blasting it to near oblivion and then analyzing for metals by atomic absorption spectrometry and/or mass spectrometry.

Would I be guessing correctly that most home chemists would benefit from employing classical wet methods of qualitative and quantitative analytical chemistry? With one of today's inexpensive balances and a 1–10-gram sample size and with readily available glassware for volumetric and gravimetric analyses you can achieve precision to 4 or 5 digits.

Just the musings of an old fart...


This is a valuable input. I like this way of thought, and I believe there is a lot of wisdom in making generous use of traditional / tried and tested methods.

I'd very much like us all also to keep pushing and discover together what is possible to achieve in terms of producing as wide a range of different metal acetates from a metal sample with a single process. One of the reasons is that it has practical applications not only for trace metal analysis but in many other useful applications as well. I was very excited yesterday as I read this thread here on SM about dissolving copper (known for its fairly low reactivity) with acetic acid. I think this has been achieved as well with silver (not only yet less reactive than copper, but known to mostly form very insoluble salts). These are just examples of all the myriad of things I believe can routinely be made in the home-lab with this fairly weak and very natural (from an anthropological standpoint) acid.
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[*] posted on 27-7-2022 at 02:55


Your only real option is to test both methods on actual samples and see what happens.



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[*] posted on 27-7-2022 at 05:39


Quote: Originally posted by Fulmen  
Your only real option is to test both methods on actual samples and see what happens.


I think there are many methods to be devised. Are you referring to (1) Method 1 as: Acetic Acid + Water + H2O2, and (2) Method 2 as Acetic Acid + Water + NaCl + Air?

Do you have a suggestion for a fairly accessible alloy to try methods on as a good but sufficiently challenging starting point? I know there's a couple (very few) elements that only form very insoluble acetates, so it will only work on alloys containing them in trace amounts, but I think most alloys aren't based on these elements. I don't quite remember which elements these were whose acetate salt is very insoluble but I remember there were very few of them (like two or three), and then a dozen maybe with medium low solubility but still high compared to that of low solubility compounds of other salts. So I think the general focus simply is on making all the different metals react and dissolve fast enough in a single evolutive medium: all the challenge is there. My understanding of the dynamics of chemistry is too poor however to be able to understand how simple or complicated that can be. I only have basic and mostly practical chemical experience.
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[*] posted on 3-9-2022 at 10:21


https://pubs.acs.org/doi/10.1021/j100181a084

Quote:
Acetic acid/acetate is a well-known stabilizer of aqueous O3 solutions


With proper safety precautions of course.




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[*] posted on 3-9-2022 at 12:55


Quote: Originally posted by VeritasC&E  

this can be useful to perform a very fine analysis of complex metal alloy composition, for instance, or to perform trace metal analysis


Would a reagent that would bring everything into the solution at once would make the sample very difficult to study???

The process of finding trace metals is a tedious one. That's why so many years of research went into finding easier, more accurate, and nondestructive methods with the smallest samples.

It's baby steps to perform the same analysis by "wet chemistry", requiring larger samples and destructive techniques.

I've done a lot of assaying over the past few months and have the advantage of knowing someone who owns an x-ray spectrometer and they are happy to tell me when I'm way off on my analysis.
But I got it easy, as I am only testing for precious metals, and these tests are very well documented.

The theory is, by knowing what metals react with what anions, as the sample is processed with different reagents, you can separate different metals into different solutions.

I had a mystery a few weeks ago. I was running a chlorate cell and had an unexpected color change caused by an alloyed cathode.

Out of curiosity, I went through the process of identifying the transition metal contamination. Took about 10 hours to identify 1 element. Went to the pawn shop and they verified my findings in less than 5 seconds.
I love living in the future

I would love to hear how a real chemist does this
But what i did was take 8 test tubes, each with 5ml of sample plus 10ml of water.
Added different reagents to each then noted if a reaction took place.
Then gogle google goollgle

Then more test. 3 of my tubes had a precipitate, so I dried them, stuck them in the oven, and ramped up the heat 50c at a time. Noting melting points, color change and decomposition.

Quote: Originally posted by CharlieA  


Would I be guessing correctly that most home chemists would benefit from employing classical wet methods of qualitative and quantitative analytical chemistry? With one of today's inexpensive balances and a 1–10-gram sample size and with readily available glassware for volumetric and gravimetric analyses you can achieve precision to 4 or 5 digits.


I would enjoy any and all reading material, guides, threads you have available on that subject please.




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[*] posted on 3-9-2022 at 14:31


Quote: Originally posted by Rainwater  
Quote: Originally posted by VeritasC&E  

this can be useful to perform a very fine analysis of complex metal alloy composition, for instance, or to perform trace metal analysis


Would a reagent that would bring everything into the solution at once would make the sample very difficult to study???



Per my limited understanding the highest end modern trace analysis techniques require all elements to be brought into solution (so samples are digested with HF / HCl / HNO3 and sometimes a mix of some of them such as Aqua Regia). The machines are then discriminating the atoms / ions on the basis of various physical characteristics (e.g. based on their mass-to-charge ratio using a magnetic field).
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