If a patent contains an ingredient in a product ,along with many other ingredients ,stated to be used for one application,would I get a patent on one of the ingredients for a use not stated and un obvious.The ingredient is a natural one ,just being used for something it has never been used for.
It depends on the patent and the jurisdiction. Is it a "composition of matter" patent on the ingredient? Or is it a process patent about how to use the ingredient to achieve a certain result?
If it's just a common natural ingredient (like, say, water) then the first patent shouldn't affect your ability to patent a process that puts that ingredient to a different use. But, without details, nobody can tell you for sure -- check with a patent attorney.
Here's an example of how this could bite you: It could be, for example, that the first patent is a patent for making a type of bread using a specific ingredient, and you want to make a somewhat different type of bread, using the same ingredient. In that case, it's very likely that the first patent covers what you want to do under something called the "doctrine of equivalents."