Sudan IV, 25g

Sudan IV has been used industrially to color oils, waxes, shoe polish, greases, oily-resin lacquers, varnishes, cellulose acetate and acrylic resins, and in wood stains. As a biological stain, it is used primarily to stain lipids and fatty substances present in cells and tissues. The color imparted is a function of the solubility of the dye in the substance affected and does not involve chemical bonding. A saturated solution in isopropanol is prepared for use as a fat stain in animal tissue. Sudan IV is a lysochrome (fat soluble dye) predominantly used for staining triglycerides in frozen sections, but which may also stain some protein bound lipids in paraffin sections. It is less popular than Oil Red O as it has a more orange shade. This red β-naphthol disazo dye has the same basic structure as Sudan III with two added methyl groups. This makes it a deeper, more intense stain, but with the hydroxyl group in the ortho position, it has similar physical properties and is fat soluble.