[Anomander]

Hi All,

I need to selectively precipitate Tungsten from a basic solution containing mainly Molybdenum.

Concerning this interesting constellation I have a couple of questions:

1. Is there any possibility to selectively test for tungsten? I need a cheap Laboratory method (without any expensive Equipment involved)

2. Is there any insoluble tungsten compound that is easy to precipitate? I will be happy with something that will even precipitate some of the Molybdenum as well.

Thank you very much for your help and I am looking forward for some interesting discussions

[gritch]

Sounds like a crown ether would work for this case. I'm not sure which type of crown ether would exactly work but one that could selectively bind to either the Molybdenum or Tungsten would help. A quick came up with nothing for me and given how similarly sized both metals are it might not possible but it's a thought at least.

[vex]

Do you know the oxidation states of tungsten and molybdenum in your solutions? If you have tungstate (WO₄^2-, W⁶⁺) and molybdate (MoO₄^2-, Mo⁶⁺), then adding any soluble salt of a divalent transition metal such as manganese nitrate will give you a mixture of metal tungstates and molybdates. If your goal is just to quantify the amount of tungsten in your solution, you could then do some powder x-ray and Rietveld analysis. If you actually want to separate them, this obviously won't work, and I can't think of anything that will help you. Maybe some sort of high-pressure anion-exchange column?