β-crystalline modification of diasazo acid dyestuff

摘要: A crystalline modification, designated "β", of the dye structure ##STR1## The β-crystalline modification is easier to isolate from water and gives filter cakes higher solids color content. β-form also more suitable for making liquid formulations dye; have lower viscosity better dispersion stability than non-modified form. β-modification obtained by heating an aqueous slurry at about 90°-95° C. pH 8.5 9.5 until complete. Debye-Scherrer X-ray diffraction patterns substantially different