Sciencemadness Discussion Board - Dissolving silver

Dissolving silver

plante1999 - 14-1-2012 at 10:10

I dont have nitric acid so I attempted to disolve silver with 3% H2O2 and 5% Acetic (vinegar) , I own 1g of silver , I will buy more sometime , I also aded 1keyboard mylar which contain silver but no copper/gold. The theorical ratio for disolving silver is about 15ml acetic acid and 15ml H2O2 but I used an exess , I used 30ml acetic acid and 40ml H2O2 and waithed 30minute , I tested for silver with HCl and I got a positive result!, but I can not even see the difference on my 1g silver piece , my scale give my a 0.01g less silver on my piece , so I suppose there is 0.01g+ in the sol. .

I will ad photo/video later.

Is there anybody here that have similar process for disolving silver?

[Edited on 14-1-2012 by plante1999]

blogfast25 - 14-1-2012 at 10:29

Ermm... three methods: nitric, nitric and... erm... nitric.

There really isn't much else that works and isn't a slow boat to China.

Try perhaps the "poor man's Aqua Regia": HCl + KNO3.

Use the search facility, if you haven't already.

AirCowPeaCock - 14-1-2012 at 10:37

You wouldn't get very far with nitric alone anyways. I dont think a mix of HCl and KNO3 would work either. But 20 g 12M HCl added to 10 g NH4Cl fromcold packs oughta work..

Mailinmypocket - 14-1-2012 at 11:03

HNO3 dissolves Ag to form Ag(NO3)2

AirCowPeaCock - 14-1-2012 at 11:26

Ive heard it forms a layer around it of silver oxide from the oxidizing properties of HNO3 protecting it. But Ive never done it myself..

Lambda-Eyde - 14-1-2012 at 11:34

Quote: Originally posted by Mailinmypocket

HNO3 dissolves Ag to form Ag(NO3)2

No, silver form monovalent ions (with a few exceptions), so the salt you get from dissolving Ag in HNO3 is AgNO3

Quote: Originally posted by AirCowPeaCock

Ive heard it forms a layer around it of silver oxide from the oxidizing properties of HNO3 protecting it. But Ive never done it myself..

That happens with >95% HNO3, but not the more common azeotropic solution. Copper won't dissolve in fuming nitric acid, but it dissolves readily with copious formation of nitrogen oxides in the 70% solution.

plante1999 - 14-1-2012 at 12:39

A quick video for SM users only.

<iframe sandbox width="420" height="315" src="http://www.youtube.com/embed/mOPiEZCf7ko" frameborder="0" allowfullscreen></iframe>

[Edited on 14-1-2012 by plante1999]

[Edited on 14-1-2012 by plante1999]

Mailinmypocket - 14-1-2012 at 13:35

Quote: Originally posted by Lambda-Eyde

Quote: Originally posted by Mailinmypocket

HNO3 dissolves Ag to form Ag(NO3)2

No, silver form monovalent ions (with a few exceptions), so the salt you get from dissolving Ag in HNO3 is AgNO3

Ah right, I was thinking of lead nitrate! Thanks!

cyanureeves - 14-1-2012 at 14:11

i've used nitric acid. someone on this forum wrote that hot concentrated sulfuric will work.i have electrolyzed silver in ammonium hydroxide and got a deep blue solution similar to prussian. the silver collects on the bottom as a sponge sandlike substance.

phlogiston - 14-1-2012 at 14:39

The "poor man's nitric acid" (HCl + KNO3) probably won't work because silver will precipitate as insoluble AgCl.

AJKOER - 15-1-2012 at 09:43

OK, your method of acetic acid/H2O2 has worked fine for me with periodic stirring. However, the reaction proceeds slowly (in a day or more, the solution will develop some gray color as some of the Silver acetate breaks down and releases Ag). Caution, although the reaction is slow, I still manged to make an obvious damaging cavity in a Sterling silver candle, having left it in the solution for a week.

Note, Silver acetate is NOT soluble in water, but does dissolve in acid solutions (like Acetic). So upon neutralizing the solution, white Silver acetate will precipitate. Reacting with NaHCO3 will result in yellow Silver carbonate.

[Edited on 15-1-2012 by AJKOER]

cyanureeves - 15-1-2012 at 11:26

its been a while since i've done anything with silver so i'm going to try it with kodak developing acetic acid and peroxide.

Aqua_Fortis_100% - 15-1-2012 at 13:30

Whats interesting! Congrats Plante1999.

I was under impression that silver only dissolves on dilute HNO3 acting on it. Now, a complete home method to process silver mylar keyboards!

But I prefer x-rays scrap.. these are much richer in Ag!

Hope this wont be off topic, but since you people are talking about dissolving silver from keyboard, it would be nice to talk also about other scrap sources of Ag here..

Acetate/protein bearing silver particles (like on x-ray sheets..black parts) and other photographic scrap, can be process in another way (still oxidizing, but alkaline way).

The yield could go up to 5g Ag/m^2 x-ray.

Ive found that other Ag scrap, like X-ray can easily be processed with home bleach (2% bleach is just fine), it is very easy to do..

The gelatinous material used in photographic emulsions consists primarily of proteins which under the action of the alkaline bleach are hydrolyzed slowly crumbling and releasing silver dispersed therein. So the silver can be attacked by the hypochlorite:

4 Ag + 2 ClO- + H2O -----> 2AgCl + Ag2O + 2OH-

You could easily reduce then AgCl/Ag2O with hot NaOH/sugar solution. The mud containing non-hydrolised matter , Ag, AgCl and Ag2O is reduced by NaOH/sugar because beyond it will hydrolise all the organic remnants from bleach step, in hot alkaline-reducing media, all AgCl is converted in Ag2O which oxidizes sugar to CO2, formic and levulinic acid (you can see acid smell during this step, even though solution is alkaline) and gets reduced back to elemental Ag..

Get a shallow plastic or glass container and dilute 2% NaOCl bleach with water (3:2).

Put in cut squares of your x-ray scrap:

Bleach will eat x-ray film very fast, leaving transparent celluloid behind..

After done, spray it with water on the shallow dish, to bring down stuck AgCl..

Treated films.. It tooks about 10 mins to make about 4 foils (that were cut in smaller squares to fit in the dish..)

Plasticware dish with AgCl

Carefully decant (it may take a day):

And reduce with hot NaOH/sucrose:

Unfortunatelly I dont have photo of the actual process, but is very simple.. The colour of mixed solution quickly turns light brown, dark brown then grey/black.. Will try to make a video next time I put my hands on more x-ray films...

Filtering (neutralize it with mild acid BEFORE you filter, since hot NaOH solution will eat your filter paper. I learned this through bad way)..

Save the filter paper used to filter Ag. It is impregnated and could be processed later along with other silver scraps with dilute HNO3 (or Plante1999 proposal of acetic/H2O2 )

Ag powder from previous runs:

There are of course patents of process.. e.g.
http://www.freepatentsonline.com/3960550.pdf
though this is a bit different and harder to do at home.. But gives ideas on how to melt/purify your silver..

AJKOER - 15-1-2012 at 15:38

Some of the chemistry per my research, see "The principles of chemistry", Volume 2, by Dmitrïi Ivanovich Mendelieev.

From the bottom of page 403:

"This is how he describes the phenomenon which then takes place: if silver oxide or carbonate be suspended in water, and an excess of water saturated with chlorine be added, then all the silver is converted into chloride, just as is the case with oxide or carbonate of mercury, and the water then contains, besides the excess of chlorine, only pure hypochlorous acid without the least trace of chloric or chlorous acid. If a stream of chlorine be passed into water containing an excess of silver oxide or silver carbonate, while the liquid is continually shaken, then the reaction is the same as the preceding; silver chloride and hypochlorous acid are formed. But this acid does not long remain in a free state; it gradually acts on the silver oxide and gives silver hypochlorite. If, after some time, the current of chlorine is stopped but the shaking is continued, then the liquid loses its characteristic odour of hypochlorous acid, while preserving its energetic decolorising property, because the silver hypochlorite which is formed is easily soluble in water. In the presence of an excess of silver oxide this salt can be kept for several days without decomposition, but it is exceedingly unstable when there is not an excess of silver oxide or carbonate present. So long as the solution of silver hypochlorite is shaken up with the silver oxide, it preserves its transparency and bleaching property, but directly it is allowed to stand, and the silver oxide settles, it becomes rapidly cloudy and deposits large flakes of silver chloride, so that the black silver oxide which hud settled becomes covered with the white precipitate. The liquid then loses its bleaching properties, and contains silver chlorato iu solution,...."

And from the bottom of page 404:

" In this manner the reactions whiih are consecutively accomplished may be expressed by the equations:

6Cl2 + 3Ag2O + 3H2O = 6AgCl + 6HCl0; 6HCl0 + 8Ag20 = 3 H20 + 6AgCIO;
6AgClO = 4AgCl + 2AgCl03.

Hence, Slas gives the following method for the preparation of silver chlorate. A slow current of chlorine is caused to act on oxide of silver, suspended in water, which is put into a state of continuous movement. The shaking is continued after the supply of chlorine has been stopped, in order that the free hypochlorous acid should pass into silver hypochlorite, and the resultant solution of the hypochlorite is drawn off from the sediment of the excess of silver oxide. This solution decomposes spontaneously into silver chloride and chlorate. The pure silver chlorate, AgClO3, does not change under the action of light. The salt is made ready for further use by drying it in dry air at 150°. It is necessary during drying to prevent the access of any organic matter; this is done by filtering the air through cotton wool, and passing it over a layer of red-hot copper oxide."

LINK:
http://books.google.com/books?pg=PA403&lpg=PA403&dq=...

So either the presence of free Chlorine in the bleach (which effectively lows the pH by forming HCl and also HOCl), or by the direct addition of a weak acid (like CO2 or vinegar) forming HOCl, which reacts directly with Ag2O or AgCO3 to create the highly unstable silver hypochlorite. Then, AgClO quickly disproportionates into AgCl and AgClO3 unless there is an excess of Ag2O or AgCO3 to promote the stability of the Silver hypochlorite.

I had added NaClO to Silver acetate dissolved in Acetic acid. The bleach and weak acid formed HOCl, which then reacted with Silver acetate to form a white precipitate of AgCl. The solution also bubbled for a few weeks (O2 from the decomposition of AgClO3).

[Edited on 15-1-2012 by AJKOER]

plante1999 - 15-1-2012 at 16:12

Silver chlorate would be a fantastic solube silver salt if it was easy to make!

cyanureeves - 15-1-2012 at 17:36

the silver i use came from x-ray film used in a hospital.it was given to all hospital employees as a yearly bonus in the form of a 99.99 1 troy ounce silver coin.

LanthanumK - 16-1-2012 at 06:39

I recently dissolved silver wire with HAc/H2O2. It did not work with ordinary shiny silver wire. However, I "activated" the wire by anodizing it in concentrated sodium chloride solution. The electrolysis soon stops and a white crust of silver chloride is visible on the wire. Place this corroded wire in the HAc/H2O2 and catalytic decomposition results, while a cloudy Cl(-) contaminated AgAc solution leaves the silver wire. In a day, the silver wire is disintegrated.

AJKOER - 16-1-2012 at 11:01

Quote: Originally posted by plante1999

Silver chlorate would be a fantastic solube silver salt if it was easy to make!

Plante1999:

See my reference on Silver Chlorate formation. Here is another one:

Source: "A comprehensive treatise on inorganic and theoretical chemistry, Volume 2, by Joseph William Mellor, page 271. To quote:

"L. N. Vauquelin found that when chlorine acts on silver oxide diffused in water, a mixture of silver chloride and chlorate is formed, and it was accordingly supposed that these same products are obtained when chlorine acts on the salts of silver. The products observed by L. N. Vauquelin were shown by A. J. Balard to be end products, being preceded by the formation of silver hypochlorite. According to A. J. Balard, finely divided silver immediately decomposes hypochlorous acid with the evolution of oxygen, and the formation of silver chloride. Again, if an alkali hypochlorite be treated with silver nitrate, or if silver oxide, Ag20, suspended in water, be treated with chlorine, much heat is developed and silver chloride and silver peroxide are precipitated while a liquid with bleaching properties is formed. The liquid is very unstable, and decomposes in a few minutes with the separation of silver chloride and the formation of a soln. of silver chlorate which does not bleach. If an excess of chlorine be employed, all the silver is precipitated and a soln. of hypochlorous and chloric acids remains. If an alkali hydroxide be added to the bleaching liquid, oxygen is evolved, and a mixture of silver chloride and peroxide is precipitated. Similar results are obtained if an aq. soln. of silver chlorate, nitrate, or acetate be employed except that the corresponding acid is liberated. J. S. Stas has •shown that probably no chloric acid or silver chlorate is formed in the primary reaction:

Ag20+2Cl2+H20=2AgCl+2HCl0

If the silver oxide or carbonate be in excess, the silver oxide gradually forms silver hypochlorite,

2HOCl + Ag20 =2AgOCl+H20

which is readily soluble, and the soln. is stable so long as it is shaken with the excess of silver oxide present. This salt is partially decomposed on standing in darkness, and completely decomposed at 60° into silver chloride and chlorate:

3AgOCl=2AgCl+AgCl03

and the latter remains in soln. in the alkaline liquid. J. S. Stas found no signs of the formation of perchloric acid. F. Raschig prepared silver hypochlorite by the action of alkaline sodium hypochlorite on silver nitrate, and also by adding a soln. of silver nitrate to sodium azide, NaN3, or to a soln. of chloroazide in sodium hydroxide."

LINK:
http://books.google.com/books?pg=PA271&lpg=PA271&dq=...

So the formation of Silver Chlorate is apparently not slow and one can actually visibly observe the formation of the AgCl. I suspect that AgClO3 should be quickly be employed in a reaction, or dried per the directions, as the aqueous solution is most likely not stable. In fact, Mellor (cited previously), page 340, notes that AgClO3 decomposes into AgCl and O2 in the presence of HCl, HNO3 and even Acetic acid. Chlorine also reacts forming AgCl, HClO3 and O2.

To comment on why one would not try to make AgClO3 as the soluble salt of choice is that only 1/3 of the Silver metal is converted into a soluble salt.

In addition to the aqueous stability issue of AgClO3, the generally slow dissolution of Silver metal itself into a salt and the cost of the acids, the main issue of say large scale production of, for example KClO3 (by adding KCl to AgClO3), remains the inherent cost of the Silver itself even with recycling.

[Edited on 16-1-2012 by AJKOER]

plante1999 - 25-1-2012 at 10:02

This weekend I will try the mixed H2O2/acetate/NaClO process to get silver from keyboard mylar.

thanks Aqua_Fortis_100% for the idee.

report this weekend.