# Niobium (V) Fluoride becoming sticky

Today I was making a pastille of Niobium Pentafluoride powder. The procedure includes a 6 ton squeezer, precision wipes, silica gel, filter papers and acetone.

The first suspicious part was that on product details, $NbF_5$ was suppossed to be $5\mu m$ powder. Instead it looked like having hair(forgive my bad terminology but I am not a chemist, but a physicist and I don't know how to describe it).

The procedure is the following.

1. Acetone and wipe papers$\rightarrow$clean squeezers parts(made of stainless steel)
2. Powder gets into the squeezer(using a funnel made of the filter paper) and gets pressed
3. The powder becomes a pastille.
4. It is stored in a plastic bottle, with Silica gel.

The filter paper is also used to fill the bottle with silica gel(as a funnel) as well as a way to store the pastille while filling the bottle with silica gel.

I have made several pastilles with the exact same recipe(i.e. $B,\;ZnF_2,\;LiF$ etc) and everything went fine. This powder however became very sticky. I have also noticed that while it's stored in the silica gel box, there are some drops inside the bottle.

So I have some questions... First of all why did it became sticky and secondly why the powder wasn't actually a powder?Is it typical for $NbF_5$?

From the properties block on the Wikipedia page for $\ce{NbF4}$:
• $\ce{NbF5}$ also seems to have a tendency to oligomerize/polymerize, as suggested by the tetrameric structure displayed on the Wiki. The only article I found in a quick search that directly mentions $\ce{NbF5}$ polymerization is this (in the abstract). – Nicolau Saker Neto Feb 7 '14 at 11:45