The Ricca Chemical EP reference solution in brownish yellow color has a composition of 97.08% water, 1.08% ferric chloride hexahydrate, 1.01% hydrochloric acid, 0.59% cobalt (II) chloride hexahydrate and 0.25% copper sulfate pentahydrate. It is suitable for use as a coloration standard. It can be stored at a temperature of 15 to 30 degree C.