I'm looking for some definite information on heating sodium bicarbonate (baking soda) to produce sodium carbonate for homebrewed darkroom recipes. So far what I've read seems to indicate that the process isn't particularly critical: heat 'til moisture's evaporated; done. Info from the following URL seems to corroborate this: http://chemmovies.unl.edu/chemistry/smallscale/SS043c.html Does this sound about right? No particular testing necessary to confirm that one does indeed have sodium carbonate and not bicarb? Also, can heating be done in the microwave rather than on a stovetop or in a conventional oven? (Fact is, I've already done this - I'd just like some assurance that what I have is in fact sodium carbonate.) Thanks, all.