Black cocaine, also known as Coca Negra, is a mixture of regular cocaine base or cocaine hydrochloride with various other substances. These other substances are added * to camouflage the typical appearance (pigments and dyes, e.g. charcoal), * to interfere with color-based drug tests (mixing thiocyanates and iron salts or cobalt salts forms deep red complexes in solution), * to make the mixture undetectable by drug sniffing dogs (activated carbon may sufficiently absorb trace odors).