# Silver chloride and ammonia



## relpub3

How do you recover all the silver from an ammonia solution you have used to dissolve silver chloride (used in refining of karat jewelry)?

Thanks

Alberto


----------



## lazersteve

The silver ion formed in the reaction is Diamminesilver (I) otherwise known as Tollens’ Reagent. Adding Karo syrup to the basic solution and gently heating will return the elemental silver. You can make a silver mirror using this very same reaction if done properly.

Steve


----------



## relpub3

Thanks for the answer Steve, I appreciate it. 

as a follow up,

I read that ammonia and silver chloride when mixed and dried can create something explosive. Is this true?

If so, then I guess I have to use Karo syrup to recover the silver right away before anything dries up. Please confirm.

I am always wondering if sugar syrup instead of corn syrup (in Karo syrup) can be used instead. Please confirm.

thanks for all the help

Alberto


----------



## lazersteve

Alberto,

Yes silver chloride and ammonia will form an explosive mixture if allowed to react for a long period of time.

You can use sodium hydroxide to convert the silver chloride as well. If ammonia is used be sure the solution is made basic before adding the Karo.

Sugar syrup will not promote the conversion.

Steve


----------



## goldsilverpro

Over the years, I have witnessed several explosions created from ammoniacal silver (azides can form) and gold solutions. Elsewhere on this forum, I suggested that, immediately after dissolving the silver chloride in ammonia, that one should acidify the solution with HCl. This re-precipitates the silver chloride, which can then be treated with Karo syrup and NaOH. *Never let the ammonical silver solutions sit around without acidifying first.*

Since witnessing these explosions, some 40 years ago, I have never used ammonia to dissolve silver chloride, except for using it as the final leach for pure gold powder.

Karo syrup (corn syrup) is glucose. I think that some other types of sugar can be used but, experimentation would be required. For 31.1 grams of silver chloride, it takes 10 mL of Karo syrup, 15 grams of sodium hydroxide, and about 100 mL of water. The sodium hydroxide converts the silver chloride to silver oxide and, then, the Karo syrup converts the silver oxide to silver metal.


----------



## lazersteve

GSP,

On the subject of exploding silver compounds.. do you know of a way to render the ammonical silver to a safe state if you have formed any? Is acid addition a viable option after the explosive silve has formed or only prior to it forming?

Thanks,

Steve


----------



## goldsilverpro

I really don't know the answer to that, Steve. I think that once you've made it, you're stuck with it but, I may be wrong. I decided to never use ammonia, except for the final cleaning of gold powder. Silver azides form only under certain conditions but, I've never gotten a straight answer as to what those conditions are.

You can also use sodium thiosulfate (photo hypo) to dissolve silver chloride. Zinc dust or steel wool can then be used to drop out the silver. Separating the silver from the excess zinc or iron is another story.


----------



## lazersteve

After Googling silver azide, I found this interesting chart from a US Department of Energy Document:

[img:388:364]http://www.goldrecovery.us/images/shock_compounds.jpg[/img]


Steve


----------



## peter i

It is not silver azide that is formed from an ammoniacal silver solution. The azide ion is N3- (The azide ion is a deadly poison, by the way).

As far as I know, the product is just called "fulminating silver" (which isn't the same as silver fulminate, a well described compound). 
It is far more sensitive than silver azide, which can in fact be handled and has some practical uses. (There is quite a bit of controversy regarding to what it really is that is formed)

The azide ion is a deadly poison, by the way.

Adding hydrochloric acid to the solution, will neutralize the ammonia, and precipitate the silver as silver chloride.


----------



## Lou

Er, maybe I should clear some of this up.

--Proper Tollens' reagent is made with ammonia water and silver nitrate, not with silver chloride. And you ALWAYS make it when you plan to use it, and store it in small quantities. 

--Tollens' reagent is very commonly used to qualitatively test for aldehydes, so any sugar will do the trick. So will formaldehyde solutions... but they all produce mirrors. That's why it's best to make AgOH first from NaOH + AgCl, then add the sugar. (Unless you're in the business of coating everything with silver mirrors, you have no business trying to drop silver from Tollens'  )


--Karo syrup is actually dextrose, not glucose. 

--Dissolving silver chloride in ammonia (to my knowledge and experience) will not make a Tollens' reagent capable of forming an explosive nitride. I have stored ammoniacal silver chloride solutions for months and never had silver nitride (misnamed as ''fulminating silver'') precipitate out. Never. With silver nitrate, that is a different story. 

--The explosive produced is supposedly silver nitride, not azide (this is where the wikipedia article is bullshit). It's definitely not fulminate, fulminates are organic. General consensus is that it's silver nitride and some other weird nitro-silver compound(s). Azide isn't formed. While most all azides are potent primary explosives themselves, they're made from soluble sodium azide, which, as has been mentioned, is about as toxic as cyanide. And we have no business playing around with NaN3 here since we're not making explosives or dismantling airbags.



Conclusions: none of us here really should be dissolving silver nitrate in ammonia, as it's really not a good way to recover bulk silver. It is however a cool thing to show your kids (I make Christmas ornaments from clear glass baubles). But you NEVER keep ammoniacal silver nitrate solutions just sitting around.

I've used the ammonia water for separating silver chloride from lead chloride many times and it works excellently. Reacidification with HCl breaks the complex, and drops out the pure silver chloride.


----------



## lazersteve

Lou,

Thanks for clearing up all the confusion over silver compounds and ammonia. This is all good information.

I've used ammonium hydroxide many times to separate silver chloride residues from other PMs. I've always converted it back to silver chloride with HCl immeadiately after dissolving it. I guess I was a little overly paranoid after hearing about 'silver azide'.
:lol: 
Thanks, 

Steve


----------



## Lou

Eesh, I would be too though. Silver and lead azide are both used in detonators. They're scary, and hell, they'll explode just by the weight of their crystals if not properly prepared (usually gelatine is used to prevent large crystals forming).


----------



## Lino1406

Sodium thio sulphate in basic solution


----------



## Irons

Lou said:


> Eesh, I would be too though. Silver and lead azide are both used in detonators. They're scary, and hell, they'll explode just by the weight of their crystals if not properly prepared (usually gelatine is used to prevent large crystals forming).



The polysachharide Dextrin is preferred because the resulting Azide mixtures are easier to handle and don't stick to the equipment.

Sodium Azide is what is used in vehicle air bags as a Nitrogen generator to inflate the bag.

Azides are nothing to fool with.


----------



## austexjwlry

I worked with explosives on an almost daily basis perforating etc. oil wells for many years. I must mention the potential danger from static electricity generated by your clothing and the electrical potential in any small storms in your vicinity other than the obvious lightning! Under certain conditions only millionths of a volt pushed by millionths of an amp is all that is required to start an explosive reaction! 

All it can take is a two-way radio, cell phone, wireless computer, microwave communication or radar tower or Vor/Tacan/loran site nearby. Even running a onan type generator or automobile nearby can be all it takes!

Stray voltage is much scarier to me than shock-sensitivity. Once in late 1984 I witnessed my own body being blown about 30' high and about 30' over while working offshore Louisiana!

Do not play or experiment with any potentially explosive material !!!

Sincerely,

Wayne


----------



## arthur kierski

whem adding ammonia to silver chloride to complex the silver does one uses heat or just room temperature?


----------



## Lou

Room temperature with lots of shaking.


----------



## arthur kierski

thanks Lou----i did not take the photos yet---as soon i photo the lab,i send it to you


----------



## Blacktoadd

Use ammonium Hydroxide or Ammonium Chloride? What about PH, acidity or basic? I tried to disolve a little of a white crystol, nothing happened, Heated it as if it was Lead chloride, still sat there.


----------



## Lou

It will be basic, as you are using ammonium hydroxide, which is really ammonia.


This will give diamine silver chloride.


Lou


----------



## Blacktoadd

Ammonium Hydroxide may be used alone to Disolve silver chloride if used in sufficient quantities to turn the solution basic. 

Ammonium Chloride needs the Prior addition of Sodium Hydroxide to turn the solution basic and oxidize the silver.
The ammonium Chloride will disolve the silver oxide. 

Am I correct that the ammonium chloride is not adaquate at raising the PH.


----------



## Lou

Second statement is correct. Ammonium chloride is weakly acidic, it being the salt of a strong acid (HCl) and a weak base (NH3). By adding base to ammonium chloride one will generate ammonia which will dissolve in the extra water giving an ammonia solution. Ammonia water is cheap though as it is used all the time in cleaning. If one wishes to concentrate it, it will be in one's best interest to add a strong base solution to ammonium chloride and then bubble the ammonia gas through your weaker ammonia water solution. It can become a very concentrated solution then. 

I should emphasize that ammonia is a very dangerous base--it easily gases a person; this gas gets into the eyes and does:
NH3(g) + H2O(l) --> NH4+ OH- which will damage the eyes.

While a basic (NaOH) ammonium chloride solution can work, it will not work as well because there will be a greater concentration of chloride anion.


----------



## arthur kierski

i have a solution of nitric acid on which i added nacl,so in the botton of the becker i have silver chloride +lead chloride--.can i filtrate the solution and add to the chlorides nh4oh,filtrate again to eliminate the lead and them add karo to precipitate the silver?
if so is the silver pure to melt and sell?
i am asking because i use silver chloride +steel wool and is a very tyring method and i always end with silver mixed with silver chloride


----------



## peter i

Lead chloride is sparingly soluble in hot water, so washing with that should remove limited quantities.

EDIT: As Lou originally posted; if there is a lot of lead in the precipitate, precipitating everything as chloride, washing the chloride with water, then selectively dissolving the silver chloride with ammonia, discard the undissolved lead chloride (in an environmentally responsible way), re-acidify the ammoniacal solution with more hydrochloric acid is the way to go.
.... the silver chloride should become quite clean from that procedure, by the way!

How much lead do you have in your alloy?


Iron is rather bad for the reduction, anything more noble than iron will also be reduced to the metallic state, and iron is a bad contaminant in silver alloys for jewellery.


A better approach would be to precipitate as chloride, wash thoroughly with several batches of boiling water (until no PbCl2 precipitates from the wash-water on cooling, or a test with potassium iodide is negative), then reduce with zinc or aluminium.

Or even better:
"Cement" with copper, thus leaving anything less noble than copper in the solution (including the copper), wash, dry and melt the silver powder. 

The second approach will give a far better product than reducing with iron, and should you then run the silver in a silver cell, the result will be very fine silver. (99.99 or 99.999)


----------



## arthur kierski

thanks peter, i will do what you advised and then give you a return


----------



## peter i

arthur kierski said:


> in about 2kilos of silver chloride i suppose 100 to 200grams of lead chloride



OK, The solubility of lead chloride in boiling water is 33 grams per litre, if we take it conservatively, and assume that not more than 20 grams is dissolved under practical circumstances, that will mean at least washing with ten litres of boiling water.

Its is doable, but draining it as dry as possible, then dissolving in concentrated ammonia and precipitating again with hydrochloric acid after discarding the insoluble PbCl2, would be my preferred method in this case.

One kilo of AgCl is approximately = to 7 mole, as it forms silverdiamine, we need two moles of ammonia per mole silver, 14 mole total.

Regular concentrated ammonia is 25% = 13 mole/litre or better, meaning that you theoretically should be able to dissolve 1 kg of AgCl in a litre of concentrated ammonia. You will need it in excess, but start by adding a litre, let is dissolve as much as possible, then pour off the solution and treat the remains with some more ammonia in small batches.
When pouring of the small batches, make them acidic and stop leaching silver when no appreciable amount of silver chloride forms.

hope this helped

regards
Peter


----------



## arthur kierski

thanks peter , you helped me a lot because my specialization is pgm--specially rhodium---but sometimes i come across some silver and gold and is good to know something about it.


----------



## skulls_box

Hi Peter, thanks for all the information.
I have just a question:
i which way can i make the solution acidic?
because the reaction is very strong with the HNO3


----------



## FrugalRefiner

Peter hasn't visited the forum in a couple of years, but as he and others mentioned, use HCl to acidify the solution and precipitate the silver as AgCl.

Dave


----------



## skulls_box

Thanks Dave you are so kind.
But i'm not sure that 1 litre of ammonium hydroxide at 25% is able to dissolve 1kg of AgCl.

Francesco


----------



## Barren Realms 007

If you use concentrated ammonia you dissolve your silver chloride you can use copper to cement it back out of solution then acidify the ammonia therfore saving the step of converting to the silver chloride to elemental silver.


----------



## sar

Barren Realms 007 said:


> If you use concentrated ammonia you dissolve your silver chloride you can use copper to cement it back out of solution then acidify the ammonia therfore saving the step of converting to the silver chloride to elemental silver.


Barren:
Is it possible to cement silver from ammonia solution with zinc powder?
If yes, can we use dilute sulphuric acid to dissolve excess zinc after cementing silver ? Isn't it dangerous to dissolve sulphuric acid in ammonia solution?
I don't have any experience in dissolving silver chloride with ammonium hydroxide
Any advice would be appreciated.


----------

