An interesting question. I've found that 15% variation in sulfite makes little difference. But 10% too much Phenidone/Dimezone can increase grain noticeably. For a concentrate, it would be helpful if both sulfite and concentrate could be measured by volume, preferably with a set of kitchen measuring spoons (teaspoon/tablespoon) or perhaps a medicine measuring cup. Either way, the sulfite would be less accurate than the liquid due to variations in compaction and fineness of the powder. I think that if a formula can give good results within a +/- 15% error in sulfite, it'll be acceptable.
Originally Posted by Rudeofus
Medicine measuring cups can be purchased in a 100-pack (!) for under $5 as in this example at Amazon. One advantage of these cups is that you can draw fill-lines at the correct levels with a black felt-tip marker, making measurement of arbitrary quantities easy.