Abstract: A process for the purification of indigo comprises treating the indigo with sulfuric acid to give indigo sulfate, separating off and subsequently hydrolyzing the latter to re-form indigo, and then treating the dye with dilute hydrogen peroxide solution.

Abstract: A process for purifying indigo comprises stripping the as-synthesized aqueous alkaline indoxylate solution before its oxidation to indigo of impurities in the absence of oxygen by distillation or by passing in steam or an inert gas and then treating the indigo precipitated on oxidation of the stripped indoxylate solution with dilute hydrogen peroxide solution.

Abstract: A process for the preparation of an indigo compound which comprises reacting a corresponding indole compound having no substituent at the 2- and 3-positions with a percarboxylic acid in the presence of an alcohol solvent, or with heating over 60.degree. C. in the presence of an aprotic solvent.

Abstract: A process for the preparation of purified indigo comprises extracting the aqueous alkaline indoxylate solution arising from the synthesis with an inert water-insoluble solvent in the absence of oxygen before oxidizing the indoxylate solution to give indigo.

Abstract: A process for the preparation of purified indigo comprises extracting the aqueous alkaline indoxylate solution arising from the synthesis with an inert water-insoluble solvent in the absence of oxygen before oxidizing the indoxylate solution to give indigo.

Abstract: An indigo compound is prepared by reacting an indole compound unsubstituted at the 2- and 3-positions with an organic hydroperoxide, preferably in the presence of a metallic compound catalyst capable of catalyzing the oxidation of the carton atom at the 3-position of the indole compound, such as a compound of a metal of group 4A, 5A or 6A of the periodic table.

Abstract: Disclosed is a process for preparing an indigo compound in improved yield by reacting indole or other indole compound having no substituent at the 2- and 3-positions with an organic hydroperoxide in the presence of an additive selected from the group consisting of (1) a carboxyl compound and (2) a boric acid ester compound. The yield of the indigo compound can further be increased by using a metallic compound catalyst capable of oxidizing carbon atom at the 3-position of the indole compound, such as a compound of a metal of group 4A, 5A or 6A of the periodic table.

Abstract: A process for the preparation of an indigo compound by reacting an indole compound having no substituent at the 2- and 3-positions with hydrogen peroxide in a liquid phase composed of at least two separate phases including an organic phase containing the indole compound and an aqueous phase containing hydrogen peroxide, or by reacting the indole compound with hydrogen peroxide in solution in an organic solvent.

Abstract: Secondary amine-terminated aromatic oligomers are prepared by conventional reactions for the formation of such polymers as polyimides, polyethersulfones and polyetherketones, using such compounds as methylamino or phenylamino anilines or phenols as endcapping agents. The secondary amine-terminated oligomers may be reacted with cyclic polycarbonate oligomers to prepare copolyurethanecarbonates which are useful as engineering thermoplastics.

Abstract: A process for forming a purified solute from an aqueous solution is provided whereby a mixture of an extractant, a hydrate former and the aqueous solution is first formed. The hydrate former forms a hydrate with water while the solute does not form a hydrate. The extractant takes up the solute from the aqueous solution. The mixture is subjected to a temperature and pressure sufficient to form the solid hydrate of the hydrate former, an aqueous solution of the solute and a portion comprising the extractant containing the solute. The solute is recovered from the portion comprising the extractant and the solute.

Abstract: Indigo dyed cotton yarn suitable for producing indigo dyed cotton knitwear, and method of producing it, comprising passing a cotton rope consisting of a plurality of yarn threads through a plurality of baths of indigo dyed liquor, allowing the dye to oxidize by exposure to air between each bath, and winding each of the said yarn thread separately to provide an indigo dyed yarn in a form suitable for knitting. The threads are wound onto individual spools, which may be rotated on a common shaft, or by individual motors. The indigo-dyed knitted cotton fabric produced shows the fading by abrasion, rather than washing out, normally associated with denim.

Abstract: A process for the preparation of deeply colored organic pigments by crystallizing finely divided crude organic pigments, whose primary particles have a size of .ltoreq.0.2 .mu.m, in C.sub.3 -C.sub.5 -alkanes, C.sub.3 -C.sub.5 -alkenes or C.sub.1 -C.sub.3 -chloroalkanes at from 40.degree. to 250.degree. C. to under atmospheric pressure or superatmospheric pressure, and isolating the pigment.The pigments obtained by the process give deep, brilliant colorations.