# interfering species in the determination of Ni using DMG



## tsangchuiyi (Mar 1, 2015)

Hi guys,

What metal ions are the interfering species in the determination of nickel using the dimethylglyoxime method. Suggest a solution to this problem.


I know the interfering species inculde Fe2+, Co2+, Cu2+. Are there anymore? 
Actually I don't know the reason why Fe2+, Co2+, Cu2+ are interfering species. Can somebody explain to me?
Please suggest a solution to this problem.

Thanks.
TCY


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## Lino1406 (Mar 5, 2015)

To get copper and cobalt out is easy. Copper in this environment
is either black or blue, what interferes.


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## tsangchuiyi (Mar 6, 2015)

Lino1406 said:


> To get copper and cobalt out is easy. Copper in this environment
> is either black or blue, what interferes.



So how can I get out Cu? My sample is Ni-Cu alloy.


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## FrugalRefiner (Mar 7, 2015)

tsangchuiyi said:


> So how can I get out Cu? My sample is Ni-Cu alloy.


You shouldn't need to worry about the copper. When I mixed my first batch of DMG, I tested it on some filings from a U.S. five cent coin known as a nickel. The alloy used to make these coins is 75% copper and 25% nickel. The DMG worked just fine, turning the classic pink color. Actually, if you look very close, you'll see tiny specks of red, which, from a little farther away present a pink color. I wouldn't think the copper would be an issue if you're just trying to detect the presence of nickel.

Dave


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## goldsilverpro (Mar 7, 2015)

tsangchuiyi said:


> Hi guys,
> 
> What metal ions are the interfering species in the determination of nickel using the dimethylglyoxime method. Suggest a solution to this problem.
> 
> ...


Where did you read that Fe2, Co2, Cu2 are interfering ions? What I read was that the only strongly interfering ions are auric, cobaltous, and dichromate. Au+++, Co++, and Cr2O7-- These can interfere because of their intense colors.


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## tsangchuiyi (Mar 8, 2015)

FrugalRefiner said:


> tsangchuiyi said:
> 
> 
> > So how can I get out Cu? My sample is Ni-Cu alloy.
> ...



My sample is Ni-Cu alloy and the interfering species should be Cu2+. So how can I remove Cu2+ to ensure that dimethylglyoxime ligand will react with Ni2+ only?

TCY


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## goldsilverpro (Mar 8, 2015)

Have you tried dissolving a little and testing it as is? The only reason Cu++ might be a problem is because it is an intense blue when made ammoniacal. Dilution might help.


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## Lino1406 (Mar 9, 2015)

Cu will dissolve in concentrated nitric acid while nickel and iron are passivated. Co dissolves in
any acid, although it may take time


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## goldsilverpro (Mar 9, 2015)

Lino1406 said:


> Cu will dissolve in nitric acid while nickel and iron are passivated. Co dissolves in
> any acid, although it may take time


With a Cu/Ni alloy, once the copper is nearly gone, the nickel will start dissolving in hot 50/50, or a bit weaker, nitric. Nickel will also slowly dissolve in hot 37% HCl.


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## FrugalRefiner (Mar 9, 2015)

goldsilverpro said:


> Lino1406 said:
> 
> 
> > Cu will dissolve in nitric acid while nickel and iron are passivated. Co dissolves in
> ...


If it's very finely divided, it will dissolve even without heat. I filed the edge of a nickel for my DMG test. I added the filings, a few drops of distilled water and a few drops of nitric to a white plastic spoon. I checked on it a couple hours later and everything was dissolved. I added several drops of ammonia and a couple of DMG and got a very pretty pink.

Dave


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