Zinc Is determined colorimetrically in beer and brewing materials by means of di‐beta‐naphthylthiocarbazone. This reagent forms a complex with zinc which is soluble in carbon tetrachloride giving a cherry‐red solution. The zinc is determined by the mixed colour method of colorimetry, using a light filter with maximum transmission at 5,500 A. Interfering metals are removed by a preliminary extraction as diethyl‐dithiocarbamates. The range covered by the method is from 0 to 16 μgrn. of zinc, enabling determinations to be made of as little as 0.01 p.p.m. of zinc in liquids or 0.05 p.p.m. in solids.