Sciencemadness Discussion Board - Silver Nitrate and Sodium Chloride.

Silver Nitrate and Sodium Chloride.

aga - 23-6-2014 at 11:13

Why nobody mentioned this reaction before is a mystery.

Two colourless liquids.
Mix.
Instant poached eggwhite in a beaker !

Wunderbar !

vmelkon - 23-6-2014 at 11:18

Maybe because it turns brown over time.

[Edited on 23-6-2014 by vmelkon]

aga - 23-6-2014 at 11:25

What happens to it as it ages ?
Decomposes into brown stuff ?

(sounds like me after a night out)

blogfast25 - 23-6-2014 at 12:30

Aga:

The formation of silver chloride is so well known you won't find much reference to it here. I did use it very recently, here:

http://www.sciencemadness.org/talk/viewthread.php?tid=30479&...

Silver chloride is light sensitive and darkens upon exposure to light: the basis of silver chloride photography.

The cheesy look of the precipitate has been observed and described by many. I don't have an explanation for it.

aga - 23-6-2014 at 12:57

Quote: Originally posted by blogfast25

The formation of silver chloride is so well known you won't find much reference to it here.

It's only well-known when you know it !

Edit : Goes grey under UV light cos it decomposes into Ag and Cl₂.
No wonder it goes grey fast on the Costa del Sol.
Gonna put it in the Sun for a while tomorrow then start all over again, and do some 'photography' with it.

Great fun !

[Edited on 23-6-2014 by aga]

CHRIS25 - 23-6-2014 at 13:56

You probably don't have the means to create a digital negative? Have you got any 35mm negatives? Transparency that you could print on? Because then you could place this on top? Place glass on top of this if you can squashed down on top of negative tightly..with paper clips or strong clipping or celotape the edges. The chemistry of the old fashioned photography is so exciting. Black and white and van dyke browns and callitypes, there is a huge resurgence in this and many serious photographers are returning to this because of the synthetic and often un-real appearance of digital imagery these days. This is how I began my journey in chemistry.

aga - 23-6-2014 at 14:04

Digital negative ?
I can print on acetate thru a laser printer if thats any good ?
Will give it a go tomoz

blogfast25 - 24-6-2014 at 04:16

Aga:

Now you've 'discovered' AgCl, perhaps you could do a Mohr's titration for chlorides?

http://en.wikipedia.org/wiki/Argentometry#Mohr_method

I can send you a 'mystery chloride' to analyse, if you like.

aga - 24-6-2014 at 11:25

Quote: Originally posted by blogfast25

Now you've 'discovered' AgCl, perhaps you could do a Mohr's titration for chlorides?

Cool ! Bring it on !

In the meantime i'm trying to figure out what hapened to my silver.
I left the AgCl outside in very strong sunlight, and it went grey.

I read that it decomposes to Ag and Cl2, so after it all went grey, i poured off the liquid and added fresh nitric acid.

Nothing happened !

Chemisty has stolen my silver.

blogfast25 - 24-6-2014 at 11:35

When it's still grey it's kind of an ill-defined mixture of silver and silver chloride that won't respond very well to nitric acid. Pure, fine (granulometry) silver powder is black.

Take a small amount of the grey stuff, put it in a test tube and add quite a bit of ammonia solution. Observe.

I'll send you some 'mystery chloride' for you to analyse. It's a simple binary chloride of the general formula MCl and the sample can be considered 100 % pure MCl. Agent aga's assignment is to figure out which is the mystery element M, by means of Mohr's titration of a solution of MCl (it is water soluble).

[Edited on 24-6-2014 by blogfast25]

aga - 24-6-2014 at 11:42

Will it self destruct in 10 seconds ?

blogfast25 - 24-6-2014 at 11:45

What? You should not be so presumptuous, mon cher.

[Edited on 24-6-2014 by blogfast25]

aga - 24-6-2014 at 11:58

Quote: Originally posted by blogfast25

Take a small amount of the grey stuff, put it in a test tube and add quite a bit of ammonia solution. Observe.

Done.
The ammonia slowly and deliberately stole the rest of my silver.

Some gas was evolved.
Didn't seem like hydrogen (no pop) but maybe there wasn't enough.

blogfast25 - 24-6-2014 at 12:06

Ag+ forms a very strong, colourless complex with ammonia: silver diammine or [Ag(NH3

2]+. This complex is so strong it causes the insoluble AgCl to dissolve in a solution of ammonia.

Are you sure it wasn't just a few bubbles sticking to the tube or the silver chloride?

aga - 24-6-2014 at 12:09

Definiately some Gas evolved.

Not a huge amount, but enough to get a pop when releasing the pressure (thumb over end of test tube).

Maybe it was ammonia wanting freedom from the rapidly shaking environment.

Edit:
Anyway, between Sunlight and Ammonia, i have lost all my Silver.

The Robbery Reaction shall it be dubbed.

[Edited on 24-6-2014 by aga]

blogfast25 - 24-6-2014 at 12:11

Quote: Originally posted by aga

Maybe it was ammonia wanting freedom from the rapidly shaking environment.

Entirely possible!

Just leave the rest of your grey AgCl/Al mixture exposed to light for a few days. Stir once in a while. It'll go black. At that point you can dissolve it in strong, hot nitric acid again..

[Edited on 24-6-2014 by blogfast25]

aga - 24-6-2014 at 12:16

so .... now that the Silver is in a complicated relationship with ammonia, while the previous girlfriend is still hanging around, how to extract it without upsetting the 'partners' ?

MrHomeScientist - 24-6-2014 at 12:21

I just used the subject reaction in a STEM camp I helped teach last week, to get kids interested in science careers. We did some "forensic chemistry" to figure out the composition of an unknown white powder using several wet tests for the anion and a flame test for the metal cation. Silver nitrate was our test for chlorides. (It's actually a test for halides in general, but in our case we limited it to Cl^- to save time. I also discovered during the camp that it's a test for carbonates too, as it also forms a precipitate with that ion as well. The silver carbonate we saw was tan to brown in color, so it's easily distinguishable from the halide precipitates.) Lots of fun!

If you haven't done it before, try the 'silver tree' experiment!

blogfast25 - 24-6-2014 at 12:34

aga:

Strongly acidifying the silver diammine complex should destroy it, because ammonia (NH3) cannot exist in acid conditions because it forms ammonium (NH4+

ions.

Alternatively reduce the silver complex to silver (metal) + ammonia with Al foil for instance.

Try two tubes to test both scenarios.

[Edited on 24-6-2014 by blogfast25]

aga - 24-6-2014 at 13:05

Cool !
So much stuff to try.

Thankyou.

aga - 25-6-2014 at 04:45

Quote: Originally posted by MrHomeScientist

try the 'silver tree' experiment!

Neat ! It works !

AJKOER - 1-7-2014 at 12:12

Quote: Originally posted by aga

Why nobody mentioned this reaction before is a mystery....

The main reason is perhaps Silver nitrate is a highly valued reagent and expensive. The products, Sodium nitrate and insoluble/unreactive Silver chloride, much less so, on both regards.
---------------------------------

I also would avoid experimenting with soluble Silver salts (like AgNO3) and ammonia . Left on its own, there is a high tendency of silver diammine hydroxide to breakdown on standing, or by accidental dehydrating with an alcohol or NaOH, to so called 'fulminating silver'. The latter has a long history of tragic accidents even when left in solution. No reason to add to it.

[Edited on 1-7-2014 by AJKOER]

[Edited on 2-7-2014 by AJKOER]

blogfast25 - 1-7-2014 at 12:30

Quote: Originally posted by AJKOER

I also would avoid experimenting with Silver salts and ammonia. Left on its own, there is a high tendency of silver diammine hydroxide to breakdown on standing, or by accidental dehydrating with an alcohol or NaOH, to so called 'fulminating silver'. The latter has a long history of tragic accidents even when left in solution. No reason to add to it.

[Edited on 1-7-2014 by AJKOER]

Another half truth. Yes, blahdiblahdiblahdiblah to fulminating silver. But the experiment of dissolving small amounts of AgCl in ammonia is a classic class room experiment, so innocuous it is. To get from a weak solution of AgCl in ammonia to fulminating silver isn't that easy. Just don't keep these solution for long, make sure they can't evaporate and dispose of safely and the risk is basically zero.

[Edited on 1-7-2014 by blogfast25]

AJKOER - 1-7-2014 at 21:03

I have edited my comment and now it is pretty much in line with Wikipedia's article on Fulminating Silver.

I agree with Blogfast that AgCl in aqueous ammonia is not generally considered a path to Ag3N. I was referring (and now very clearly) to soluble Silver salts, especially AgNO3.