At the grocery store, I set off to the dairy section and when I had no luck there I headed for the aisle that contained condensed milk. I mistakenly thought (as the name would imply), that cream of tartar was some sort of cream. I tracked down a store employee who looked like they might bake (i.e. a woman in the bakery section versus the 15 year old boy in the produce isle). She promptly took me to the spice aisle. It's a powder sold with the spices!
After I got it home, I got curious about what exactly this stuff was. Here is what the jar says; "Cream of tartar is indispensable for a number of cooking and baking applications. Essential for use as a stabilizer for beaten egg whites, it is commonly required in angel food cakes and meringues. Cream of tartar helps prevent the crystallization of sugar in candy making and is often an ingredient in fondants and fudges". Ingredients: Potassium Bitartrate.
Despite a number of university chemistry courses under my belt, I felt no closer to understanding what this ingredient was. So I dug a little deeper. Turns out is is an acid.