How to Sharpen tungsten needles?

[Jim Bone]

In article <2tq19m$mis at usenet.srv.cis.pitt.edu>, lxzst+ at pitt.edu
(Liminzheng) wrote:

> I need to sharpen tungsten needles for dissecting the flies. I was told
> that there is a chemical way to do this. Does anyone know the recipe?
> Any advice will be much appreciated. 

Fix a length (5 cm) of 0.4 mm dia. tungsten wire to the end of pasteur
pipette or glass rod by melting the end of the rod in a burner first. Next,
heat sodium nitrite in a nickel crucible over a bunsen burner until it is
molten.  Dip the wire repeatedly in the nickel and remove it quickly. 
Examine the wire under a dissecting scope and repeat dipping until the
desired point is acheived.  The end of the wire is dissolved in the sodium
nitrite--since the tip is immersed longer, it is dissolved more, forming a
tip.


JB