Metal Complexes of Alizarin V–Investigations of Alizarin–dyed Cotton Fabrics

It has often been assumed that the oil used in the traditional Turkey Red dyeing processes is an essential constituent of the dye complex formed on the cotton fibre. Work is now described which shows that the same complex is formed in vitro and on cotton fabrics mordanted with aluminium salts in the presence of calcium ions, both in absence and in presence of oils, e. g. Turkey Red oil; the formula of the complex is CaAl(OH)(Az)2. Factors governing the deposition of the complex within the cotton fabric are discussed. For level dyeing, fixation of the mordant should take place at pH 8, which is also the optimum dyebath pH; in the dyeing process itself, alizarin should be present in excess of the amount necessary for complex formation.