Minerals that are used by the body, cannot be absorbed in their metallic form. (they are usually toxic that way or burn the stomach).

So they are combined into an ionic form that dissolves in water in the stomach contents and then can be absorbed.

Sodium chloride is table salt...this is a good example. Sodium in metallic form explodes in the air..and is demonstrated in school experiments often.

Chloride, sulfate, oxide, bicarbonate, are common carriers therefore you see on labels on supplements. Even some complex combinations using amino acids called chelates. These are sometimes called "salts" meaning mixtures like table salt is.

So potassium chloride is the most common form we see.
The value of the weight of the combination is often quoted. But only the elemental content is really used by the body. (the potassium in potassium chloride would be less that the total weight stated). Many supplements today are including elemental values and state as such...but many still do not and it is misleading to the public who don't understand this distinction.

This is one explanation on the web:
http://www.chiroweb.com/archives/16/25/18.html

If you go to a nutritional site for food contents... the potassium listed there is only the elemental content of any salt present:

This link:
http://nutritiondata.self.com/facts/...roducts/2461/2
For a serving of kale shows mineral content as elemental.

I would not use a potassium source without first getting tested at your doctor's. Using too much potassium can be dangerous if you also are on certain drugs, or have some kidney problem that conserves potassium. Potassium is plentiful in food. You can get all you need from food. The link above will illustrate content for you to see what you are eating. Pay attention to serving size.
For example....one can of V8 has over 800mg of potassium in it.
And Gatorade is a very poor source at 35mg/serving.