Quantitative Analysis Mixed Iron And Nickel Salts

[unigirl]

I need to find out how much elemental nickel is in a mixed sample of Iron (III) oxide, Nickel (II) Acetate. What's the simplest method?

thanks

[gingejbee]

Weigh sample...then use the fact that one of them is very soluble in water and the other is insoluble in water to separate them. Filter off the insoluble one, dry and weigh. That'll tell you how much of the soluble one you had in the original sample....then use it's formula to calculate the amount of the element in that amount of compound.

[theprof]

X-ray fluorescence would be fairly easy given that you have access to the equipment but you might well need additional calibration. Consult a technician. Obviously more complex instrumental methods are available.

Failing that try Gravimetric Analysis. Add Dimethylglyoxime to the solution, filter the startlingly pink precipitate ( Lady Penelope would be ecstatic!), dry and weigh it. Vacuum filtration would be best. You should be able to achieve a 0.1% elemental mass accuracy or even better with a suitable balance.

[theprof]

It's far better and easier to remove and weigh the nickel component of the mix using Dimethylglyoxime. You should be able to do the calculation in your head without having to resort to a calculator or sheet of paper and pencil. Don't waste time and effort by calculating backwards needlessly.

Besides, in some circumstances iron (iii) oxide will form a solute in water and it cannot be filtered off as a result. Can you suggest what these circumstances could be?