Silver chloride and ammonia

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

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

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

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

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.

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

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.

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

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.

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.

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

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).

Sodium thio sulphate in basic solution

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).

Click to expand...

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.

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

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

Room temperature with lots of shaking.

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

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.

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


This will give diamine silver chloride.


Lou