.2 may be hydrogen, or alkyl containing from 1 to 4 carbon atoms, R.sub.3 may be hydrogen or phenyl with or without agrouping such as R and X may be hydrogen, chlorine, bromine, SO.sub.3 H or COOH.Due to the strongly polar hydrophilic property of the pigments represented by the above general formula, moist press cakes of these pigments, upon drying, tend to form hard agglomerates and aggregates.