using ki, easier to get where swim is
As long as it scaled for the proper # of moles that shouldn't bee an issue.
Dry the h3po4 before reaction
I don't know, maybee you could try it both ways, this reaction hasn't been documented very well as far as I remember. You could make a valuable contribution. Take good notes and post your experiences. The merck index says Phosphoric acid heated/boiled to 150C becomes anhydrous. Keep in mind that its melting point(anhydrous) is ~42C.
dry the DMSO too?
This link has good info on drying DMSO and really good all around DMSO info.
http://www.gaylordchemical.com/products/dmso/applications/pharmaceutical/default.asp (http://www.gaylordchemical.com/products/dmso/applications/pharmaceutical/default.asp)