Well, I suppose you do! (You really want to say "aren't they?" rather than "don't I?") And yes, they are. However, as I think Eric was getting at, saying "there is much salt" or indeed "much food" or "much noise" or using "much" like that with any other mass noun is not at all colloquial and sounds formal to the point of being stilted. People just don't say it, which is odd, because there is no such issue with saying the plural counterpart, e.g. "there are many glasses on the table", or using it in the negative, e.g. "there is not much salt on the table".