Novel improved single-phase mixed crystals of monoazo dyes laked with alkaline
earth metal cations and ammonium cations in a molar ratio of about 1:2 having a
fine particle size and substantially better fastness properties than similar known
products are excellently suitable as tinctorially strong pigments. Also claimed
is a process for the preparation of a single-phase mixed crystal pigment of formula
##STR1##
wherein E is Mg, Ca or Sr, by crystallisation from an inert hydrophilic liquid
in the presence of solvated catiens E++, NR5R6R7R8+,
x is a number from 0.33 to 0.62 and y is a number from 0.76 to 1.34, and the concentration
of solvated catiens E++ at the beginning of the crystallisation is higher
than the concentration of solvated cations NR5R8R7R8+.
