"Dark chocolate" is the general term used for chocolate that contains chocolate liquor -- and usually additional cocoa butter, sugar, lecithin (as an emulsifier), and flavorings -- but little or no milk. While there is general agreement that this term refers to chocolate that contains less than 12 percent milk solids, there seems little consensus on the minimum chocolate-liquor content required of the dark-chocolate category as a whole or of the individual varieties of chocolate within that category.
In Europe, for example, dark chocolate must contain at least 35 percent chocolate liquor and have a cacao content of at least 43 percent. In the United States, on the other hand, the government requires a minimum of only 15 percent chocolate liquor for this category. But here are some rough guidelines for understanding the varieties of dark chocolate that are available in the United States:
Sweet dark chocolate. This is the U.S. government's name for dark chocolate, and by legal definition, it must contain at least 15 percent chocolate liquor. The mildest dark chocolates typically have a cacao content of 15 percent to 34 percent.
Semisweet dark chocolate. This sweetened dark chocolate is often sold as "morsels" or "chips" for use in chocolate-chip cookies and other baked goods, although it can also be found in bar form. According to the U.S. Food and Drug Administration, semisweet chocolate must contain a minimum of 35 percent chocolate liquor. Its cacao content is typically in the 35 percent to 49 percent range. Technically, semisweet chocolate contains a higher percentage of sugar (and therefore a lower percentage of cacao) than bittersweet chocolate does, but the terms are sometimes used interchangeably, and semisweet chocolate can be substituted when a recipe calls for bittersweet.
Bittersweet dark chocolate. Bittersweet chocolate is sweetened dark chocolate that, according to the U.S. government, must contain a minimum of 35 percent chocolate liquor. Most bittersweet chocolate bars have a cacao content of at least 50 percent, and some have a cacao content approaching 100 percent. As the "darkest" of the sweetened dark chocolates -- the variety that has the highest cacao content -- bittersweet chocolate has the most intense chocolate flavor.