Tellurium (400 mesh) is not getting dissolved in Top( Trioctyl phosphine), where as 200 mesh size Te is dissolving..After all Te is forming coordinate bond with TOP ( Outer 5p shell of Te can accept the unpaired electrons from TOP) and thereby dissolving ( forming a colorless solution). So why it shows different reactivity according the mesh size?
The number of openings in one inch of screen represents the mesh size.
Thus, 200 mesh corresponds to 74 microns and 400 mesh to 37 microns.
Interesting question! Usually smaller particles will dissolve more easily, so your observation goes against common experience. You might check the packaging information to see whether a coating has been applied to the smaller particles. I have been surprised by such coatings in the past.
Please check this site "http://www.netafimusa.com/files/literature/wastewater/Mesh-vs-Micron.pdf". It might be of interest for you.
In my experience tellurium is much more prone to oxidation than selenium, and it can cause problems when making TOPTe. Colleagues have encountered a grey residue, probably an oxide, that would not dissolve. Finer powder just has more surface area to oxidise. I would usually go for Te shot and either grind it just before dissolving, or heat and wait for the reaction to complete. If available, store the tellurium power in a glove box right after purchase and do all of the reaction with TOP there.
I think you have already obtained the proper answers you need. It depends upon the method used to make the tellurium metal. If grinding is used to make the powder, then the heat produced by grinding causes the surface of the particles to oxidize. Try heating both sets of particles and you will likely see a difference in the rate in which the particles dissolve in the TOP. Also, try washing the particles in cold acid (dilute phosphoric & then dry-?}. I expect that you will be able to obtain a solution much easier. - RC Ropp
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