Stannous Chloride Test

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aga

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Prompted by Göran to do the 'acquaintance tests' i thought it best to do a bit of maths first, instead of leaping straight in and botching it again.

Hoke's recipe in chapter IX, page 93 translates to :-
1.56g tin chloride crystals
23 ml water
2 ml HCl (30 drops were measured to find out)

SnCl2, Tin(II)chloride normally comes as the dihydrate (SnCl2.2H2O) giving 1.31g of actual SnCl2 in 23ml water + 2ml HCl.
That works out at 0.28[M], or 53,000 ppm concentration.

Lazersteve's recipe :-
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=41&t=5271#p45030
2g tin Powder
30ml HCl
This works out as 0.56[M], or 106,000 ppm concentration, about 2x the strength of Hoke's.
His photos show how excellent the colours come out.

Hoke's 'Two Grains in 2 oz Standard Gold Solution' recipe on the same page translates from grains/oz to :-
0.13g gold
57ml acids/water
= 0.012[M] , or 2400 ppm concentration of chloroauric acid.

Making that from clippings off a 1g .999 ingot took about 2 hours before all the 0.13g of gold had dissolved (no heating).

Using the Stannous Chloride i made earlier, 2ml of the solution was put in a plastic cup and diluted first with 2ml distilled water then 4,8,16,32 and so on, in order to halve the concentration each time.
Each concentration of solution was tested with the SC.

Even the use of the SC test needs some practice, as i got different results depending on which solution the test paper was dipped in, then had a drop of the other applied, or if both were applied as drops.
Also the amount of solution seems important - too much and not much happens.

So, here are the results at 2400ppm, 1200, ppm etc down to 37ppm gold concentration :-
ppmColours.gif
The 75ppm photo doesn't show much, but a hint of brown was seen with the naked eye.

The most Amazing part is that the SC test easily shows up 150 parts-per-million, which would be a mere 0.09g of gold in 1 litre of solution !

This SC test shows Negative to a concentration below about 70 ppm, so it cannot be used as a 'there is No gold' kind of test, meaning that those very dilute values need be accounted for, if not eventually rescued.

Now, i cannot trust that i've made the stannous chloride solution correctly, nor that i'm using it right by putting it on cheap filter paper, mostly because the colours are not clear.

Chances are that something went wrong when i made the SC solution, so some tin(II)chloride crystals have been ordered so that a testing solution can be made as per the book.

P.S. i think i got the maths right, and checked them twice. There could still be errors though.

Edit: hopefully edited some errors without multi-posting
 
Nice post! I like it! 8)

I make my stannous by dissolving as much tin as I can in a bit of HCl, then I test it against a standard solution I have. It works for me. The make up and concentration isn't critical.

To test I dip the top of a q-tip in the solution, drawing up a bit of liquid but not saturate it. Then I use a pipette to put some stannous solution on the other side so the solutions meet in the middle and often shows a clear purple line where the liquids meet.

Göran
 
Most use Stannous as a qualitative test rather than a quantitative test Aga.

i.e. Is there gold in there or not? Simplest way to make it is some tin solder in HCl or pewter in HCl. A jar lasts for yonks provided it's not left open.
 
g_axelsson said:
Just edit the original post and I'll remove the two next ones.
Editing done.

Yes. Please delete the second and third posts.

To have even Botched an Edit ... Gah ! It'll be a Miracle if i ever refine any Gold into a button !

I like the idea of the reagents converging to form a line.
 
anachronism said:
Most use Stannous as a qualitative test rather than a quantitative test Aga
Some say they can get a ballpark idea by the SC result, which is why i tried to put some numbers on it.

anachronism said:
i.e. Is there gold in there or not?
That's my point about to 70ppm thing really - it cannot be used as a gold-present/gold-absent test.

Certainly an 'is-it-worth bothering' test, but not a 100% 'there is No gold' test.
 
How long after the initial drop of stannous were the pictures taken?

Was the nitric killed off of the auric chloride firstly?

I believe I have read that stannous can be as sensitive as 4ppm. But, I don't know if that is something you can "take to the bank" as far as accuracy goes. But, it does make one wonder. Since hoke says the excess acid needs to be killed off. I wonder if it is all neutralized (the nitric anyways) if the test would be more sensitive and get down to the lower ppm range.
 
aga said:
UncleBenBen said:
Nice post aga! :D
Thanks !

The Devil speaks and once again Gold Fever strikes to the very core ! :G :roll:

You've got to keep an eye on the ol' Sly Fox. Always looking to drag unsuspecting souls down into the abyss of gold and silver! :twisted:
:lol: :lol:

Take a look at your test strips tomorrow after they have time to dry and see if there is a difference.
 
Topher_osAUrus said:
How long after the initial drop of stannous were the pictures taken?

Was the nitric killed off of the auric chloride firstly?
No. The test was done immediately - i missed the bit about getting rid of the nitric first, again :oops:

When the 'proper' stannous chloride crystals arrive i will re-do the whole thing, properly (with luck) and report the findings/images of the colours versus ppm concentration.
 
I believe Hoke goes into great detail about "testing solution A" (stannous) in her "Testing precious metals" book.
In it, she says you can simply use a flame (lighter) to heat up the drop of pregnant solution. I cannot recall exactly, but she says either add a drop of water or HCl if it dries up all the way. Then go about your testing with stannous.

That testing book of hers is great, it really really is. It is significantly shorter than "Refining precious metals", but the information contained within is remarkable. Granted, she uses a $35 ozt gold price, and pennyweight as her scale...but, still, minor details. She goes over how to discern regular nickel-white golds from platinum group ones, and the flame test, etc... If you have yet to read it, it should really be one of the next things you do. You will not be disappointed.
 
Topher_osAUrus said:
How long after the initial drop of stannous were the pictures taken?

Was the nitric killed off of the auric chloride firstly?

I believe I have read that stannous can be as sensitive as 4ppm. But, I don't know if that is something you can "take to the bank" as far as accuracy goes. But, it does make one wonder. Since hoke says the excess acid needs to be killed off. I wonder if it is all neutralized (the nitric anyways) if the test would be more sensitive and get down to the lower ppm range.


4 ppm sounds right to me
 
Still reading the first, but already have the second book downloaded.

It will take about a week for the SC crystals to arrive, so should have read them both by then.

After that, another attempt at emprical testing to see if 4ppm is achiveable by a noob.
 
aga said:
Still reading the first, but already have the second book downloaded.

It will take about a week for the SC crystals to arrive, so should have read them both by then.

After that, another attempt at emprical testing to see if 4ppm is achiveable by a noob.

Did you happen to check the tests at all after the pic op? Maybe the test would reveal more of its "true colors" after awhile. I believe Ben suggested to look the next day. What did they look like? Did you happen to check 30 minutes after you initially tested? An hour or two? the next day?

I've also seen posted on here, it can be done on good grade filter paper, a drop on a drop (or beside one another, letting them run into one another). Then you can see the individual lines of gold, platinum, palladium if they are there... I know palladium can be a bit of a chameleon when it comes to stannous testing. DMG is by far the definitive test for Pd.

And if Lou says that it is accurate to 4ppm, THAT is something you can take to the bank. (after bookmark searching, it was 4metals who I initially read that posted it... and both of those men, Lou and 4metals {and numerous others} you should creep their old posts... you will be amazed at what you learn)
 
Please see link:

https://books.google.com/books?id=i_JMAAAAMAAJ&lpg=PA70&ots=fKwrbf9pph&dq=detection%20sensitivity%20stannous%20chloride%20gold%20purple%20of%20cassius&pg=PA69#v=onepage&q=detection%20sensitivity%20stannous%20chloride%20gold%20purple%20of%20cassius&f=false
 
Very nice, thank you Lou

That is a downloadable pdf too, (clicking the cog in the upper right hand corner, and download pdf)
Cool. 8)
 
Thank you for the replies.

I actually binned each one after the photo :!:

Noob error, granted. Far too concerned about having a photo to post than thinking clearly.

Lou says it works to 4ppm so i will try and get as close to that as possible.

I will plan it better and try to Do it better when the SC crystals arrive.

Hopefully the gold solution was made right as that will be the basis for the tests.

0.13g of .999 gold was snipped/weighed and put in a 100ml plastic bottle with a screw-on lid.
About 8ml of 20% HCl was added, then about 2ml 56% HNO3, both from plastic pipettes.
The bottle had the screw lid put on, and then i put it on top of the air pump for the stock pot, in a way that meant it got vibrated but could not fall off. Took roughly 2 hours before the gold dissolved despite an occasional shaking by hand.

If anyone can see that was all wrong, please chime in and say how it should be done.

If i did it wrong, the tests/photos are/will be worthless.
 
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