Sciencemadness Discussion Board - Making Silver Oxide

Making Silver Oxide

symboom - 18-5-2011 at 18:16

ive found a post were some one mentions this about making silver oxide without nitric acid

Silver anode in a nitrate solution with good stirring should do it, doing it in a base solution may coat the anode too quick, passivating it. A nitrate solution will at least be easier to filter the oxide out of.

or do i really need the nitrate salt. like making copper hydroxide through electrolysis

also would HCl in hydrogen peroxide dissolve solid silver in to insouble silver chloride and from there silver oxide.

AJKOER - 18-5-2011 at 19:45

Hi:

I have an old reference that HClO (see preparation below from household chemicals) can dissolve Silver Oxide forming AgCl and liberating O2. As HClO can also be prepared from HCl + H2O2, if HCl/H2O2 etching solution dissolves silver, my guess is that it first dissolves existing Ag2O (or sulfide or carbonate), and then the liberation of nascent oxygen may be oxidizing more Ag to Ag2O, and the process continues, albeit slowly.

Perhaps a more direct approach is, as I have witness that bleach (NaClO) quickly oxidizes Iron (Fe) to rust, is to just add powdered silver to NaClO, as this would again be the action of nascent oxygen on silver (if no reaction, add H2O2 to the NaClO to liberate the active oxygen). Filter and wash with H2O2 to remove any active NaClO.

PREPARATION OF HClO: Add a weak acid to bleach (vinegar works, ascorbic, very dilute mineral acids, and even H2CO3 although this process is slower). Heat the solution which at first drives out mostly Cl2O, Dichlorine Monoxide the anhydride of HClO, and use the vapors directly or dissolve in water to create a surprisingly useful solution of dilute HClO.

cyanureeves - 21-5-2011 at 07:03

i have silver in hcl acid and hydrogen peroxide and it is not dissolving the silver as it does other metals, i've added bleach and can see some bubbles but i dont think its going to dissolve silver.the silver forms a black coating after a while and the bubbling stops.

AJKOER - 21-5-2011 at 16:07

Try adding powdered silver to a solution of NH4OH/H2O2.

The logic is that apparently NaClO, with its nascent oxygen, can form Ag2O, a black to tan salt. So H2O2 may also oxidize Ag powder as well and can be safely mixed with NH4OH (unlike NaClO which reacts with NH4OH forming vapors of the deadly NCl3 explosive and toxic amines).

Then, the ammonia will dissolve the Ag2O produced from the H2O2 forming di-amine silver hydroxide.

Ag2O + 4 NH4OH --> 2 [Ag(NH3)2]OH + 3 H2O

CAUTION: On standing this solution has, on occasion, produced crystals of the explosive, Silver Nitride, Ag3N (also, called fulminating silver, but not to be confused with Silver Azide). This compound is so sensitive that friction between its crystals has on many occasions produced injuries from 'in-solution' detonations.

As such, hopefully using the NH4OH/H2O2 solution, the silver will be oxidized and dissolved. The di-amine silver hydroxide can be heated (soon after its creation) to safely yield Ag2O, all without the use of Nitric acid.

symboom - 26-5-2011 at 11:05

Quote: Originally posted by cyanureeves

i have silver in hcl acid and hydrogen peroxide and it is not dissolving the silver as it does other metals, i've added bleach and can see some bubbles but i dont think its going to dissolve silver.the silver forms a black coating after a while and the bubbling stops.

thats interesting it desolves copper was not sur if it desolves silver

bleach desolving silver forming silver oxide not sure if that will work... hmm hypochlorous acid might work bleach and vinagar what your talking about is making a concentrated solution of hypochlorous acid
HCl wont work HClO + HCl → H2O + Cl2

cyanureeves - 26-5-2011 at 14:06

yes i know. i right away tried it even though it was sterling not 99.9 silver but it did turn slightly blue because of copper. funny how bleach and hcl acid solution will dissolve gold and so will hcl acid and hydrogen peroxide solutions.

AJKOER - 28-5-2011 at 07:59

Whatt I would try is to place silver filings in bleach. Let react until all silver is black to tan (Silver Oxide).

Then, add H2O2 to further react (liberates nascent oxygen) and also convert any unreacted NaClO to NaCl:

NaClO + H2O2 --> O2 (g) + NaCl

Filter and rinse again with H2O2. Now, you should be able to safely add NH4OH to dissolve the Silver Oxide with time.

My guess is that the finer the silver powder, the better the final result.

[Edited on 28-5-2011 by AJKOER]

The WiZard is In - 28-5-2011 at 16:25

Quote: Originally posted by symboom

ive found a post were some one mentions this about making silver oxide without nitric acid

Boy this thread has to be a new low for the madness of science.

Excuse me if I inject a little chemistry into the fun

Do you be wanting — Silver I or "II" oxide?

djh
----
Penthouse magazine founder Bob Guccione
dies at 79 21x10

DALLAS – Bob Guccione tried the seminary
and spent years trying to make it as an
artist before he found the niche that Hugh Hefner
left for him in the late 1960s.

Where Hefner's Playboy magazine strove to
surround its pinups with an upscale image,
Guccione aimed for something a little more
direct with Penthouse.

-----------
“Something a little more direct,” e.g.,
Gynecology through the picture study method.

symboom - 7-6-2011 at 17:56

well tried 6% household bleach and vinagar tested it on other metals strong gas emerged alittle bit even though the bleach had a perfume to mask the smell of the bleach then mixed with vinagar wow did it make a corrosive solution added stainless steel it started to stain.(react) well tried stainless steel for weak concentration it works quicker than i expected.
copper desolved a bit slow so im going to just make more concentrated bleach with my chlorate cell with bleaches clothes very fast with cold water.with normal vinagar with has to be used instead because bleach and hcl forms chlorine gas
which that reaction forms hypochlorous acid.

also tried a solution of peracetic acid then to dissolve at least copper did not notice any thing then slowly started to turn blue copper acetate i dont think silver acetate could be made this way.

[Edited on 8-6-2011 by symboom]

AJKOER - 9-6-2011 at 09:55

Two points.

Dilute HClO keeps much better than any concentrated solution. The reason is due to a significant disproportionation reaction (which occurs also with NaClO, Ca(OCl)2, etc.):

3 HOCl --> 2 HCl + HClO3

Light and heat are catalysts. There is also a decomposition reaction that occurs (depending on the source) more or less than 10% of the time:

2 HClO --> 2 HCl + O2

but can be accelerated in the presence of certain oxides (of copper, nickel, Mn, Fe and cobalt) and organic substances.

Probably most important as you may unintentionally, using old solution of HClO, create some unstable and explosive chlorates (especially ammonia and heavy metal salts).

FYI, Cl2O, which is the gaseous anhydride of HClO, reacts as follows with various metals:

Cl20 + Fe --> FeO + Cl2

Cl20 +2 Cu + H2O --> Cu(OH)2.CuCl2

2 Cl20 + 4 Ag --> 4 AgCl + O2 (gradual)

Cl2O + 2 Hg --> HgO.HgCl2 (very slow reaction)

So, for the most part, either Cl2 or O2 is liberated, and either a chloride or an oxy-chloride double salt is created.

Intergalactic_Captain - 9-7-2011 at 03:47

This thread is a month or so old, but I've got a little practical advice regarding the OP's lack of success regarding the actual dissolution of silver. The simple answer is that although HCL plus H2O2 or HNO3 or xNO3 will doubly react to form the nitrate which is then displaced as the chloride, in reality it isn't that easy...

To go this route, you need an alloy that's less than 90% silver - That rules out coin and sterling. For practical purposes, you need to go far below that. I've tried my hand at dissolving many silver alloys over the years, mainly coin and fine - Haven't found any cheap sterling to play with to date. If it's fine, any chloride process will give you one result - It'll react at first, but the speed at which the chloride forms, as a skin on the piece, is detrimental - The process essentially stops. I have a couple of scrap fine silver strips that have been sitting in aqua regia and the nitrate version for, quite literally, 2-3 years that are simply laughing at me...

Coin silver is not much better - Although the copper helps the process, it's not much of an improvement. A few months ago I went through my "pulled from circulation" pile and tossed a couple of old quarters in a HCl/KNO3 bath - There's only a miniscule (absolutely insignifigant) amount of AgCl, after 3-4 months in there (at STP), there appears to be absolutely no change in the physical surface of the coins...

...Why did I say that? I've spent a lot of time trying to find a way to refine silver without the use of nitric acid - At this point, I've realized that it's a futile effort. I'm sure there's some exotic method out there, but for the average person HNO3 is the only practical way.

...One thing I've been pondering, though, for quite some time is the idea of ultrasonicaiton - Find a sonicator that can take the chemical stress (or a toothbrush in a ziploc bag), and it might flake the AgCl layer off at such a rate that the reaction can procede at a reasonable pace - That's for the future, though...

I should probably note that this isn't something that I"m just pissing out - Silver is one of the few things I actually give a shit about. For the last ten years, on and off, I've been trying to find a "hardware store" method for extracting silver from common alloys. The only thing I've been able to gather is the the xCl methods are nothing but theoretical masturbation - The ONLY method I've found merit in is using raw HNO3 and working from there to the desired compounds.

...That said, HNO3 ain't cheap, no matter how you obtain it - Neither is silver. When I started playing around, $8/ozt was steep - 8->12>15->20->27->35->37->42->~50->~32->~36 - Check the spots - Odds are, today, at least, the nitric process is viable when the costs are balanced - If nothing else, AgNO3 is far more valuable than pure Ag on a molar basis...

Fleaker - 15-7-2011 at 16:41

Dissolve it in hot sulfuric acid, precipitate with HCl, keeping it wet, then slurry it with a 1.2 molar excess of base solution. Filter, rinse until pH neutral and you will have AgO.

cyanureeves - 15-7-2011 at 18:00

fleaker dissolve what in hot sulfuric acid? sterling?

Fleaker - 16-7-2011 at 07:34

Yes, sterling dissolves in hot concentrated sulfuric acid.

AndersHoveland - 16-7-2011 at 13:13

Chloride ions act as a sort of inhibitor, preventing corrosion of metallic silver by forming a surface layer of insoluble AgCl. That a mix of H2O2 and HCl will not dissolve silver is not at all surprising. Neither is silver attacked by aqueous chlorine. Of course, aqua regia can still attack silver.

(3)AgCl + (4)HNO3 --> (3)AgNO3 + (2)H2O + NOCl + Cl2

Note for the newbies: the above reaction only works if the nitric acid is highly concentrated >60%.

[Edited on 16-7-2011 by AndersHoveland]

Fleaker - 16-7-2011 at 20:28

Quote: Originally posted by AndersHoveland

Chloride ions act as a sort of inhibitor, preventing corrosion of metallic silver by forming a surface layer of insoluble AgCl. That a mix of H2O2 and HCl will not dissolve silver is not at all surprising. Neither is silver attacked by aqueous chlorine. Of course, aqua regia can still attack silver.

(3)AgCl + (4)HNO3 --> (3)AgNO3 + (2)H2O + NOCl + Cl2

Note for the newbies: the above reaction only works if the nitric acid is highly concentrated >60%.

[Edited on 16-7-2011 by AndersHoveland]

That reaction doesn't work at all. In any case involving Cl-, a crust of AgCl still forms. It's too favourable a reaction with AgCl being a very stable compound which I detest.

Aqua regia does not solvate much silver at all. Try and dissolve 14K gold in aqua regia and see how much dissolves due to the troublesome silver content. This is why the metal is often either atomised or alloyed down (inquarted with silver and parted with 30% nitric acid).

AndersHoveland - 16-7-2011 at 23:15

Try bubbling chlorine into AgNO3 solution. If there is no reaction then it would suggest that AgCl is not so favorable after all. Remember chlorine has an equilibrium in water.
Cl2 + H2O <==> HCl + HOCl

AndersHoveland - 28-7-2011 at 11:24

After some research,

"The ability of aqua regia to dissolve silver in gold is due both to the oxidizing power of the nitrate ion and the ability of chloride ion to form highly stable, partially covalent polyatomic ions with the metal ions once they are oxidized."

"Gold and most other metals will dissolve in aqua regia; silver, however, will form a silver chloride precipitate. Because of this reaction of silver, it is necessary to restrict the amount of silver in the start material to be refined to a maximum of 10%; any more than this will run the risk of the silver chloride preventing complete dissolution of the gold by masking it off."

"some low carat white golds contain considerable silver and are very difficult or impossible to dissolve in aqua-regia as an insoluble silver chloride film is formed which prevents further action by the aqua-regia."

"Aqua regia typically reacts by oxidizing the metal to a metallic ion and reducing the nitric acid to nitric oxide. Its reaction with silver produces silver chloride."

"[silver] will react with hot concentrated H2SO4, with HNO3, and with aqua regia." (this was from an informal chemistry site, so they may have made a false assumption)

One researcher encountered problems trying to dissolve away elemental gold, while leaving silver chloride in a photographic plate intact. “I could not employ aqua regia of the usual strength because the concentrated hydrochloric acid dissolved the silver halide at once. A success was obtained with dilute aqua regia.”

"The remainder of the silver was placed in another beaker and covered with concentrated HNO3. To this beaker was added an equal volume of concentrated HCl, forming a mixture that lacked the proportions of true aqua regia (3 HCl : 1 HNO3). As the acid attacked the silver, AgCl precipitated out as white clumps. The amount of precipitate steadily increased, peaking at about four hours. It redissolved after prolonged standing, however.
The method of using mixed HCl-HNO3 was done in this experiment to illustrate a curious situation in which Ag seems to go into solution via the nitric acid and comes right back out again as AgCl because of the hydrochloric. If we could make a diagram to show what we think is happening, it would show newly-mobilized Ag+ ions coming off the metal surface, only to form insoluble AgCl as soon as they meet up with nearby Cl- ions. It is well-known that silver chloride is highly insoluble, even in nitric acid; however, beginning chemistry texts often neglect to mention that silver chloride will in fact form a soluble complex ion (AgCl2-) in the presence of excess chloride. AgCl is therefore soluble in excess NaCl or concentrated HCl, especially when some AgNO3 is present (Merck Index, 1983).
In this experiment, much of the silver came right out of solution as AgCl. However, some remained in solution as AgCl2-. Dilution of this liquid caused more AgCl to precipitate. This tends to confirm that [Cl-]aq must be high in order to allow significant [AgCl2-]aq. Dilution favors solid AgCl over dissolved AgCl2- ions."

"solvent action of strong nitric acid upon silver chloride. A large quantity of the strongest nitric acid, apparently free from..."
http://pubs.rsc.org/en/content/articlelanding/1872/js/js8722... (perhaps someone could share with us what is in the paper)

Apparently, silver chloride does have some equilibrium with concentrated nitric acid, thus the AgCl can be dissolved, although only very slowly)
http://pubs.acs.org/doi/abs/10.1021/ja01333a009

Basically, to answer the original question, aqua regia can dissolve pure silver, but only with great difficulty.

If trying to more rapidly dissolve elemental silver with aqua regia, I think it would be important to use a much larger excess of nitric acid than hydrochloric, and use as high a concentration of nitric acid as possible (preferably over 90%, but possibly 99-100% would be required). Might try saturating anhydrous nitric acid with chlorine gas, then reacting it with silver, I bet the silver would dissolve.

[Edited on 28-7-2011 by AndersHoveland]

White Yeti - 5-8-2011 at 07:50

Perhaps if you took some silver nitrate and heated it to decomposition temperature ~450C, nitrogen dioxide with be evolved and disproportionation should yield silver I oxide.

redox - 5-8-2011 at 08:57

Quote: Originally posted by White Yeti

Perhaps if you took some silver nitrate and heated it to decomposition temperature ~450C, nitrogen dioxide with be evolved and disproportionation should yield silver I oxide.

That method won't work, I think. Silver oxide decomposes at 280C, so heating silver nitrate would go strait to the metal, skipping the oxide altogether.

[Edited on 6-8-2011 by redox]

kryss - 6-8-2011 at 15:02

You can reduce AgCl with glucose and Aluminium foil, then dissolve in Nitric.

mario840 - 8-8-2011 at 02:03

why aluminium foil ?? dextrose (glucose) will be just fine and basic solution it's important, good stirring ad heating for 1 hour and it's done , here you have (yield 100%):

kryss - 9-8-2011 at 08:57

Its from a DOE/SCA method for Chemical Oxygen Demand, for recycling Silver - which builds up in kilos, I think they do it that way as you dont need tons of hydroxide - I think the Al foil just starts it off.

AJKOER - 13-8-2011 at 09:35

I have successfully dssolved Sterling Silver in a solution of Vinegar and H2O2. The process appears slow but within 12 hours, you will have a solution of Silver Acetate.

I believe there is also a YouTube video using this method.

Adding a base (like NH4OH) will precipitate Ag2O. Note, on standing for several days, the Silver Acetate solution will breakdown by itself releasing Ag2O.

CAUTION: Unknown to my spouse, I left the Sterling Silver Candle holder in the Vinegar/H2O2 for a few days (I thought it would just clean it more). It apparently, however, cause a deep pit and invades the Candle holder from within the pit, basically badly damaging your Sterling Silver. Thus, I would not recommend this as a cleaning approach.

As I previously noted, one must take care using NH4OH owing to the possible formation of the explosive Silver Nitride, Ag3N. But how is it formed? Here is my explanation which can serve as either a route to its preparation or avoidance.

First, Silver oxide dissolves in an excess of aqueous NH3:

Ag2O(s) + 4NH3 (g) + 4H2O <--> 2 [Ag(NH3)2]OH + 3H2O [1]

Note, I have written this reaction as reversible (see as a source, "Second year college chemistry" by William Henry Chapin, page 255):

"As might be expected, the silver-ammonium complex dissociates slightly into its constituents as indicated by the equation

Ag(NH3)2+ <=> Ag+ + 2 NH3

This is a reversible reaction, very much like the ionization of a very weak acid or base."

Second, the equation for the creation of Silver Nitride can be written for one mole of Ag2O as:

2/3 NH4OH (aq) + Ag2O (s) --> 2/3 Ag3N (s) + 5/3 H2O [2]

Now, per "Comprehensive Inorganic Chemistry Series", Silver Nitride can be prepared by adding Ag2O to concentrated ammonia and letting stand in air, heating in a hot water bath (or, one can precipitate it with the addition of alcohol).

Now, my speculation as to the involuntary mechanism of Ag3N formation is that by removing NH3 from the reversible Equation [1] (remember the Ag3N preparation calls for standing in air, or heating in water bath or adding alcohol), the reaction is driven to the left as excess NH3 was originally required to dissolve the Ag2O. The freshly precipitated Ag2O can then react with the reduced amount of available NH3 per Equation [2] to form Ag3N.

As such, for safety when working with Ag2O and ammonia, it is probably best to start with concentrated ammonia and cold store the solution in a sealed container if not discarding. If not possible, at least periodically adding more NH4OH would be recommended.

[Edited on 13-8-2011 by AJKOER]

[Edited on 13-8-2011 by AJKOER]

[Edited on 14-8-2011 by AJKOER]