Antimony trichloride is the chemical compound with the formula SbCl3. This a soft colorless solid was known to the alchemists as butter of antimony. It has a pungent odor, and on contact with water, it undergoes hydrolysis, forming antimony oxychloride and releasing hydrogen chloride. Thus, samples of SbCl3 must be protected from moisture.
SbCl3 is a reagent for detecting vitamin A and related carotenoids in the Carr-Price test. The antimony trichloride reacts with the carotenoid to form a blue complex that can be measured by colorimetry.
Antimony trichloride has also been used to enhance the louche effect in absinthe. It has been used in the past to dissolve and remove horn stubs from calves without having to cut them off.