Dimethylglyoxime

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Dimethylglyoxime, DMG (IUPAC name: 2,3-Butanedione Dioxime) (CH3C(NOH)C(NOH)CH3) is a white crystalline solid that is insoluble in pure water but soluble in alcohol or a solution of NaOH, DMG has two acidic protons and thus dissolves in aqueous NaOH as a sodium salt.
It is used in detection and analyzing of nickel and palladium content in solutions. It is also used to strip palladium from silver electrolyte. It could be used in palladium refining but thanks to the high price of DMG refiners usually use classical methods instead.

Testing

Pd(II) + 2 H2DMG => Pd(HDMG)2 + 2 H+ yellow precipitate
Ni(II) + 2 H2DMG => Ni(HDMG)2 + 2 H+ intense red precipitate

In acidic solutions Pd can be precipitated selectively from nickel that will stay in solution. In alkaline solutions nickel will precipitate.

For gravimetric analyze a solution of 1% DMG in alcohol is used. When the goal is to precipitate Pd from other noble metals, an aqueous DMG solution in NaOH is usually preferred.

To prepare a DMG in 1M NaOH solution start with 4g NaOH in 100 ml distilled water, then add 5.81 g DMG and filter when it has dissolved.
To precipitate 1.00 g of Pd, 2.5 g of DMG is used. This is the same as 43 ml of the above alkaline solution. When using the alkaline solution the pH value must be kept acidic to keep nickel from precipitating.

WARNING!

When silver, nitric acid and alcohol is mixed, explosive silver fulminate can be created.
GRF : Discussion about dangers with silver and alcohol

Sellers

References

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