How can I make best capsules Kaliumiodide 300 mg?

Kaliumiodide is quite hygroscopic and can cause by causing a very high local ion strength coacervation of the gelatin, which slows the dissolving of the gelatine. That is why I think that a preferably inert filler should be diluted. The quantity to be used depends on how much is still to be replenished to have fully filled capsules.

As filler I would use talc with 1% aerosil.  

The egg must be delivered in a well-balanced bottle with a dry stopper.