1,3-Naphthalenedisulfonic acid, 6,6'-((3,3'-dimethyl(1,1'-biphenyl)-4,4'-diyl)bis(azo))bis(4-amino-5-hydroxy)-, tetrasodium salt
C.I. Direct Blue 53
An azo dye used in blood volume and cardiac output measurement by the dye dilution method. It is very soluble, strongly bound to plasma albumin, and disappears very slowly.