# Colours of Pt and Pd compounds



## jdaw1 (Sep 22, 2022)

I have a peculiar question, which might be about the compounds of platinum and palladium.

In financial markets charts, numerical graphics, are generally a mess. There is no consistency of representation. For decades I have used some standard symbols of my devising: USD is always a black 5/2 star; GBP a red diagonal cross; JPY a red circle; etc. I’m extending the list (there are about a hundred such markers), re-coding it in SVG, and when ready will open-source it under a generous licence.

The extension should include the precious metals, in their capacity as traded sort-of money. XAU and and XAG have obvious colours, and shapes of ingots in ratios determined by the Good Delivery rules. XPT and XPD must be different. Alas their colours are, for these purposes, too close to silver. I need a non-arbitrary colour for each.

Maybe that should be the colours of their florides. Or of any other compound of them which have colours distinct from each other and distinct from Au and Ag.

(Of course, I am open to a different rule by which to assign two colours, especially if all the Pt and Pd compounds are white or gold-brownish.)

And thank you for reading thus far through an unusual question.


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## goldandsilver123 (Sep 22, 2022)

Left is gold as HAuCl4
Middle is platinum as H2PtCl6
Right is palladium as H2PdCl4


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## jdaw1 (Sep 22, 2022)

goldandsilver123 said:


> Left is gold as HAuCl4
> Middle is platinum as H2PtCl6
> Right is palladium as H2PdCl4


Ooh! This is good. Progress. Thank you.

Your diagram has H₁ and H₂, and Cl₄ and Cl₆. Is the variation in colour caused by the varying numbers of non-metal atoms, or by the change in metal? If solely by the change in metal, is there a cleaner example in which only metal changes?


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## Ultrax (Sep 22, 2022)

All optical effects (in particular, the color of the solution) depend on the resulting spatial structure of the complex compound. Color can be affected by changing both the ligand and the complexing agent, including their macromolecular electrochemical interconnections (for example, by Van der Waals forces or degree of hydrocarbon polymerization). There is no consistent theory capable of predicting color based on the theoretical structure of a chemical. We only have access to past empirical experience.

Gold compounds can range in color from yellow and red to purple, green, and blue. Palladium is dark red to brown to black. Silver compounds can have colors from transparent to yellow, blue-green, and black. Platinum - from deep orange-red to yellow. And this is not all potential options.


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## orvi (Sep 23, 2022)

Platinum group metals compounds, the most likely used are they chlorocomplexes/chloroacids (or their salts) - H2PtCl6, H2PdCl4 and H3RhCl6 (or in case of Rh it´s sulfate - Rh2(SO4)3.

H2PtCl6 is yellow (diluted) to bright orange/little reddish (concentrated).
H2PdCl4 is starting with strong yellowish to reddish as concentration of it slowly rises (diluted), and end very dark red-brown, practically you cannot see through (concentrated).
Rh2(SO4)3 is deep red with smear of brown mixed in it (in solution).


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## jdaw1 (Sep 24, 2022)

Thank you. This is good, and I can work with it.


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## jdaw1 (Jan 2, 2023)

Thank you for the help with this. I said open source, so it seems polite to mention
github.com/jdaw1/chart_markers/blob/main/Documentation/ChartMarkers_Gallery.md

Platinum is the last marker in the list.


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