cream of tartar isn’t really a spice, it’s a carbolic acid —a chemical. Like baking soda is a chemical. Then why is it so much more expensive than baking soda? Thanks.
Carbolic acid is phenol, definitely not a spice. Cream of tartar is a salt of tartaric acid, and yes, a chemical. As to why it is more expensive than soda - the chemicals don't all cost the same.
I'm not a chemist nor do I play one on the Web. It is my understanding that baking soda can be mined and easily produced in large quantities. Cream of tartar is derived primarily from wine or grape juice by a process of crystallization and precipitation. Consider the cost of the two raw materials, essentially dirt v. aged wine. Therein, I think, lies a substantial portion of the price differential. In addition there is a much larger market for baking soda than for cream of tartar.