Zinc yellow is a chromate of zinc mixed with oxide of zinc. To make zinc yellow, boil separate saturated solutions (1) of 29 oz. of sulphate of zinc in water and (2) 20 oz. of chromate (not bichromate) of potash in water; mix, boil for one hour, collect the precipitate on a filter cloth, wash several times with water, and dry at a low heat. Another method is to dissolve 12 1/2oz. of bichromate of potash in hot water; mix 6 oz. of zinc oxide to a cream with water, and stir it into the bichromate solution. Allow to stand for twenty-four hours, boil for one hour, then filter, wash, and dry.