Cocoa powder is made by removing half the cocoa butter from ground cacao beans and adding baking soda to what's left to form what the manufacturing industry calls press cake, which is then cooled before it is pulverized and sifted into cocoa powder. The process of adding the baking soda to the ground cacao beans is called dutching, which is a reference to Coenraad Johannes Van Houten, the Dutch chemist who patented the process.
The process of dutching was first used in the Netherlands in 1828. It was born out of a desire to replace the hot cacao liquid that was used to make hot cocoa by combining hot water and ground cacao beans that contained the full amount of natural cocoa butter. Because water and oil are not mixable, the cacao could not be evenly disbursed in the water, and the hot cocoa was gritty and had a layer of fat floating on the top. Dutching made the drink far more palatable and revolutionized the way hot cocoa is made. The liquid cocoa butter that is pressed from the cacao beans is used in manufacturing chocolate and is also in high demand in the cosmetics and pharmaceutical industries.