A better stannous chloride method

[Dr. Poe]

A better stannous chloride method is to make up a set of papers that have been soaked in stannous chloride (containing a trace amount of stannic chloride). Hang them up on a clothes line with wooden clothes pins until they are dry.
A small drop of gold solution in the center will leave a mauve violet ring if the solution is weak. A brown spot will appear in the center of the ring if the solution is concentrated.

 

[Platdigger]

Ok, I looked up the difference between Stannous (Tin(II) chloride), and Stannic (Tin(IV) chloride).
Then looked to see if I could buy some Stannic.
I found this: Tin(IV) Chloride, 1M solution in heptane, 100ml for 37.15 from Fisher Sietific.

You know a way to make it?
Or a better (cheaper) place to buy it?










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[notch]

A better stannous chloride method is to make up a set of papers that have been soaked in stannous chloride (containing a trace amount of stannic chloride). Hang them up on a clothes line with wooden clothes pins until they are dry.
A small drop of gold solution in the center will leave a mauve violet ring if the solution is weak. A brown spot will appear in the center of the ring if the solution is concentrated.

What about Oxygen in the Air Oxidizing the Stannous to Stannic?

 

[4metals]

No different than using the standard solution on a piece of absorbent paper.

How long can "stannous chloride test papers" be stored without losing sensitivity? I'd hate to make a bunch of papers, dip themand hang them to dry to have them gobad in a week.

 

[jimdoc]

You would think that they would already sell testing papers like that if they lasted.

Jim

 

[Emmjae]

I have often thought about this too. I mostly use filter paper disks that I purchased when I first started refining for my stannous tests. Nothing special about the filter paper disks. I just found something better that I like to use.

I start off by putting a drop of my solution that I want to test on the paper first and then a drop of my stannous chloride test solution that I make. I usually make dozen or so tests before I get a new filter paper. I have had positive test results showing from an older test area that was negative when the new test area had bled into the old. The older test areas have been as long as several weeks old and the paper is stored in the open air in my fume hood.

I might try a test experiment. I'll put a drop of my stannous chloride on 5 locations of my test paper. I will do the first spot test at that time with my gold chloride I keep for testing my stannous chloride. I will then test 1 additional spot each week for 4 weeks with the same gold chloride and compare it to the starting spot.

I'll post my results and a picture when I'm done.

Mike

 

[qst42know]

I have had positive test results showing from an older test area that was negative when the new test area had bled into the old.

This seems like you are testing with too high of nitric levels.

If you get a negative result on your paper could you try heating the spot over an incandescent light bulb to drive off the nitric and test again?

I hope you aren't losing some gold to false negatives.

 

[Emmjae]

I have had positive test results showing from an older test area that was negative when the new test area had bled into the old.

This seems like you are testing with too high of nitric levels.

If you get a negative result on your paper could you try heating the spot over an incandescent light bulb to drive off the nitric and test again?

I hope you aren't losing some gold to false negatives.

You might have miss understood. I put my drop of solution to test on the filter paper first. If I get to close to an old test area and it bleeds into it, it shows positive around the edge of the old test area before I get the chance to put my fresh stannous chloride on it.

Mike

 

[qst42know]

Yes I did misunderstand.

So you are getting a positive test result from the old stannous residue.

It would be interesting how long stannous would stay viable dry on the paper.

 

[bswartzwelder]

I just bought a 1/4 pound bottle of stannous chloride on eBay for less than $20. That included shipping.

 

[Harold_V]

I just bought a 1/4 pound bottle of stannous chloride on eBay for less than $20. That included shipping.

That's a very convenient way to keep supplied with testing solution. Add a little free tin with the crystals when you make your testing solution to extend its useful life.

If you have any questions, it is well discussed in Hoke's book.

Harold

 

[sawmill]

Hello Harold

I really enjoy reading Ms. Hokes book,and I can see why you
recommend it so highly. I am a prospector ,and most of my interests
are with testing,assays,and recovery. I would recommend that any
serious prospector read that book too.

I do have a question for you. I notice that Hoke uses a different
way of making her stannous solution,other than just adding tin to HCL,
and heating. In your opinion ,is there any advantage,or disadvantage
with either formula?

 

[Harold_V]

It's been a long time since I read Hoke's comments on making stannous testing solution, but as I recall, I followed her instructions, more or less, to the letter. I may have altered the amount I made per session, but I believe I followed her advice otherwise.

Having said that, I am not in a position to comment on other procedures, not having had any experience. I can say with total honesty, if you follow her advice, you will achieve success, and more importantly, it will be reliable (it can be repeated).

Sorry I'm not more help.

Harold

 

[sawmill]

Thank you Harold
I believe I will go with Hokes method too.

 

[rusty]

A better stannous chloride method is to make up a set of papers that have been soaked in stannous chloride (containing a trace amount of stannic chloride). Hang them up on a clothes line with wooden clothes pins until they are dry.
A small drop of gold solution in the center will leave a mauve violet ring if the solution is weak. A brown spot will appear in the center of the ring if the solution is concentrated.

Dr. Poe your method of making up stannous chloride strips is the perfect solution for me. In my youth injured L1 and L2 and have some vertebrae damage in my neck now that I'm older these injuries affect how long I'm able to work especially if I'm required to stand for any length of time.

Because of my medical condition, have had to toss many stannous solutions because of aging, I can see where dry stannous chloride strips would be cost saving in the long run.

Should the strips once prepared and dried be stored in a dry dark container to preserve them.

Best Regards
Gill

 

[Dr. Poe]

I just kept mine in a drawer. I never had one go bad. Protecting from light sounds reasonable.
I once made a small experiment: Scrap gold was dissolved into AR. Roasted Gold ditelluride into Ar in another test tube. 1/4 of each was taken and mixed together. Three solutions; gold scrap, roasted gold telluride from ore, a mix of both.
A drop from the scrap onto SC paper instantly produced a brown spot surrounded by a mauve ring.
A drop from the roasted gold telluride gave a negative result. A drop from the mix also gave a negative result. I left my lab for 25 minutes or so and returned to find that all tests had turned positive. When I repeated the test, it took nearly ten minutes for the results to complete. The scrap gold came from broken jewelry. If your scrap gold comes from electronics, it's possible that you also have some tellurium in your solutions. Tellurium is in the oxygen family with sulfur and selenium.
Polonium is also in that family, but doesn't count. Dr. Poe

 

[Geraldo]

Stannous chloride is used in a classical analysis technique for selenium and tellurium. The kinetics of reaction with both Te4+ and Te6+ are very fast, and stannous chloride can be used to quantitatively precipitate Te from solution (both from sulfuric and hydrochloric solutions). So - - I would imagine that tellurium would cause all kinds of interferences with the gold stannous chloride test...

 

[Harold_V]

A better stannous chloride method

I've followed this thread with considerable interest, and I'd like to comment on the concept of *better*. I'm not convinced it's better-----just an alternate way to test.

There are times when a spot plate will serve far better. That, of course, requires that one use stannous chloride as a prepared solution.

Want an example?

You have a solution that is not well defined. It may or may not contain platinum group metals, but the bold gold reaction masks anything that may be present.

In such a case, I'd place a drop of the unknown solution in a spot plate cavity, and then add a crystal of ferrous sulfate. That would precipitate the gold, leaving the balance of the values in solution. You could then split the drop and test with stannous chloride and DMG, to determine the presence of palladium and/or platinum. The test strips are nice----but they won't replace stannous chloride in all cases.

The best equipped lab will have at its disposal all (reasonable) methods to test---including the paper strips.

Harold