Thanks PE,
I started using NH4I back befor I got a handle on Alcohol precipitation as a means by which to wash a PVA based emulsion. I was trying to minimize the content of materials that needed to be washed from the emulsion. So I used NH4Br as well as NH4I. Now that I have come to trust alcohol presipitation I should be able to switch back to KI. What about KBr vs. NH4Br, aside from adjusting for M.W? Bill