Report on making praseodymium fluoride

This was a simple procedure but being that praseodymium fluoride is probably not often heard about I decided to report.

Atomistry says PrF3 is yellow, but Wikipedia (and supplier info) says green. So I decided to make some. This was my first experiment with a fluorine compound and I thus proceeded very slowly and in small steps.

The praseodymium starting point was the solution leftover from when I made Pr(NO3)3 and should have had 15g anhydrous praseodymium nitrate in solution.

Ammonium fluoride NH4F provided the F, with the reaction being a simple double displacement. I acquired the NH4F a few days ago.

6.5g of NH4F was dissolved in 20ml water, I don't think I have ever seen a salt dissolve so fast in water, by the time I completed adding the water with a squirt bottle it was already a clear solution. This should have put the NH4F in slight excess.

The NH4F solution was slowly added to the Pr(NO3)3 solution under stirring. A light green suspension immediately formed. Stirring was continued for another 10 minutes and the solution was then gravity filtered.

The remainder was a green wet paste. See photo. This was placed in a desiccator for 36 hours. After this is was bone dry, and basically kept the same color; maybe a tad lighter. It appears very much the same when viewed in sunlight or fluorescent light.

Dry powder was 10g which was a bit more then the 9.1 aimed for. I suspect there was a bit more then 15g of nitrate in the starting solution or maybe still a bit of moisture, but it did seem very dry. I decided not to grind it into powder to reduce the chances of breathing in some.

Also attached a photo of the 4 Pr compounds made recently, different shades on green.