blueprint boiling point cas registry number chemical compound chemical formula chlorine color photography colorimeter copper crystal structure cyanotype density dye electroplating ferroxyl indicator solution heat treatment histology international union of pure and applied chemistry nomenclature ion iron laboratory list of r-phrases list of s-phrases melting point molar mass organic chemistry oxidizing agent palimpsest phenolphthalein photography potassium ferrocyanide prussian blue reagent silver sodium dithionite sodium thiosulfate solubility solution steel water wool