Process for continuous dyeing of cellulose-containing yarn with indigo in a single application while controlling the pH value

A process for continuous dyeing of cellulose-containing yarn with indigo in a single passage applies reduced indigo from an aqueous dye liquor containing deoxidants, alkali and a dissolved alkali metal salt at a concentration of 100 to 200 g/l as an electrolyte at a pH value of the liquor adjusted to about 10.2 to 11.3, while maintaining the electrolyte concentration, exposing the yarn to a gas which dissolves in the aqueous medium while forming an acid, and then oxidizing reduced indigo in the yarn to form pigment and finishing the dyeing process in a customary manner.