# Determination of Platinum Alloy(95%) by gravimetric method??



## Anonymous (Aug 11, 2009)

Hello....it is my first topic that I was released here....and my english is not good. 

That is the tesing procedure of determination platinum alloy, (Pt-95%, Pd-4%, Rh<1%, Ru<1%, Ir<1%)

*Step 1:
Weight and rotate the metal sample to a thin plate ~~~5g*

*Step2:
Dissolve/ digestion the sample by Aqua Regia*

*Step 3:
After the metal is dissolved completely in Aqua Regia, dry the acid solution that almost all convert to precipitate form*

*Step4: 
Repeat add few ml conc. HCl and a few drop hydrogen peroxide approx. 5-8 times. Add 2 ml HCl at last step and cool down in room temperature

Step 5:
Add 5g ammonium chloride to precipitate the precious metal. Then filtrate and wash the precipitate and transfer to crucible

Step 6:
Ashing the fitrate in muffler furnace

Step 7:
Weight the ashed fitrate 

Step 8:
Dissolve it back to Aqua Regia

Step 9:
Measure the solution by ICP-OES (Au, Ag, Pd, Ir, Rh, Ru, Cu)

Step 10:
Finally, Subtract the sample inital weight from the weight after ashing and ICP measurement*

I have some problems and list as following:

1)Why we need add hydrogen peroxide in step4 ,what is the function for adding?? for precipitate the gold in sample solution?? or for break down the gold molecules to nano-dimetion 

2)Is it need to add few baic buffer (e.g. pH10) before adding hydrogen peroxide??? for provide a _pH swing_???

3) Do ammonium chloride salt/solution precipitate all precious metal ??? What function on it????Only Pt or Pd can be precipitate???how about Cu???

Anybody can explain these question
Thx!!!!!!!!!!!!


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## goldsilverpro (Aug 11, 2009)

Definitely, a question for Lou.

Since you duplicated this post, I deleted the other one in Help Needed. Duplicate posts create confusion. Everything gets read, so there's no reason to post the same thing twice. No problem - a lot of new members do this until they're told.

Your English is much better than some of our US members. At least you use capital letters, when needed, commas, periods, and decent spelling and grammar.

Glad to have you aboard! Where are you located?

Chris


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## jimdoc (Aug 11, 2009)

I have noticed that the newer members to the forum do not show the location. Is this them just not entering that info, or is there a problem with that. It is nice knowing where people are, it helps in giving better answers to alot of questions.
Jim


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## Lou (Aug 11, 2009)

Welcome to the Board. I will try and address your questions and also address some of the mistakes in your testing procedure.

My answers are in red and bolded.





williamwuuu said:


> Hello....it is my first topic that I was released here....and my english is not good.
> 
> That is the tesing procedure of determination platinum alloy, (Pt-95%, Pd-4%, Rh<1%, Ru<1%, Ir<1%)
> 
> ...


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## Anonymous (Aug 12, 2009)

Sorry for my repeated topic and say thank you to Lou. I stay in Hong Kong. 

Would anybody give me some good procedure for determination Pt Alloy by gravitmetric method with the composition that I mention before?? Because I try to measure some Pt Alloy by using ICP-OES combining with internal standard method and "Blacketing techinque". However, the results is quite poor,e.g.: high RSD, so many interferece. Therefore, I am finding some procedure from book/website and do many research to improve the analytical method. Anyway, I perfer to use gravimetric method, because I done this method to analysis some 18K gold Alloy perfectly.

Thz alot.

William


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## zachy (May 15, 2017)

I have the same problem. I do not know which is the best technique to analyze platinum by icp, the procedure is complex and very few people help. If you give me a guide I can read it. Or if anyone knows I can give you money for the explanation, now I have to submit a good report in the university.

Thank you very much


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## g_axelsson (May 16, 2017)

This might be a relevant article. Discusses the precision in ICP-MS combined with fire assay for Au, Pt and Pd. Adding a bit of silver nitrate to the fire assay created a silver button that collected the PGM and gold. The silver button was then dissolved and the liquid tested in ICP-MS.

http://www.sciencedirect.com/science/article/pii/0009254194901457

Göran


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## zachy (May 26, 2017)

The problem of these ducumentos that are of payment and the university is very slow buying the texts, thank you very much for your help.

If someone else knows how to do a good trial using ICP. GREETINGS FRIENDS.


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## Lou (May 27, 2017)

The gravimetric method is with mercurous chloride and is very effective.

Spectophotometrically, you will need to download ISO 11494:2008.

Regards,


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## zachy (May 29, 2017)

Hello Lou, thank you very much, I already got the ISO 11494: 2014 standard, much more current, if they need to tell me and I can share them.

*The committee responsible for this document is ISO/TC 174, Jewellery.
This second edition cancels and replaces the first edition (ISO 11494:2008), which has been technically
revised with the following changes:*

I am also interested in the gravimetric test with mercurous chloride, which is standardized?

Thank you very much


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## Lou (Jun 5, 2017)

Mercurous chloride solution quite nasty.


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## zachy (Jun 5, 2017)

Must be also very poisonous Hg2Cl2? What percentage of precipitation do you have for platinum?

Can not make gravimetry with ammonium chloride?

Thanks Lou for responding. :mrgreen:


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## zachy (Oct 2, 2017)

Where you can get YCl3 6H2O, I have not been able to get, or Y2O3, I do not know if I need both, the method is not clear, or either of them serves me.

the truth is a longer method.

Hello,

This answers me of INORGANIC VENTURE
This is an item that we don’t carry in stock and as such would be a special project. These projects can be a significant cost in both time and material expenses. The estimated time frame I am being told is 8-10 weeks. Would you like to proceed and if so do you need a Guide 34 reference material?

Please let me know if you have any other questions or concerns.


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## Topher_osAUrus (Oct 2, 2017)

zachy said:


> Must be also very poisonous Hg2Cl2? What percentage of precipitation do you have for platinum?
> 
> Can not make gravimetry with ammonium chloride?
> 
> Thanks Lou for responding. :mrgreen:



You need to find a book or two by Beamish, he goes over gravimetric determination in great detail.
He has 3 that I have been able to procure
"Analysis of Noble Metals, overview and selected methods"
"The analytical Chemistry of the Noble Metals"
"Recent Advances in the Analytical Chemistry of the Noble Metals"


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## Lou (Oct 2, 2017)

zachy said:


> Where you can get YCl3 6H2O, I have not been able to get, or Y2O3, I do not know if I need both, the method is not clear, or either of them serves me.
> 
> the truth is a longer method.
> 
> ...




You can use yttrium oxide, Y2O3, of high purity. You can also buy yttrium nitrate. *Both of these are on ebay and very cheap. * You can also use indium as well, and just dissolve up the pure metal in aqua regia, evaporating and reconstituting with HCl.

You use yttrium to make up as internal standard in the solutions you intend to bracket, as you no doubt know already.


As for Beamish--I have his books and they are very helpful, most particularly for Os/Ru, which still are the way to go so far as I am concerned.


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## zachy (Oct 2, 2017)

Many thanks Lou for your ideas, as they are always very valuable for the study group, I will keep them very in mind.
I want to contribute the following document as study material, I found it very interesting and timely in this topic of the analysis.

had heard or read that the Indian served to analyze the gold, but not the PGM.


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