5 and a content of ca and mg ions respectively of 1 0 and 0 5 mg l is then treated with an emulsion of mineral oil and is finally dryed and taken up on a ring twister the characteristics and the advantages of the invention will be better evidenced by table 1 in which analytical data of yarns are tabulated to show the criticality of the combination of operations according to the invention comparison data have been obtained not from yarns treated with conventional processes which require a greater number of operations and much longer times therefore lower spinning speeds but with yarns which have all undergone a partial coagulation in the bath and a completion of the coagulation but have not undergone washing under the preferred conditions of the present invention in the first column of the table the elements and the quantities which have been determined are indicated column 2 illustrates the analysis of the yarn after the completion of the coagulation it is seen that the degree of white is 30 which if the normal washing and finishing treatments were carried out would be the degree of white obtained on the finished yarn requiring a separate bleaching operation in.