A STUDY ON THE CRYSTAL-STRUCTURE OF A SOLID-SOLUTION OF MONOAZOACETOACETANILIDE YELLOW PIGMENTS

A single crystal of the solid solution containing 40% mol CI Pigment Y ellow 1 and 60% mol CI Pigment Yellow 5 was obtained and its crystal s tructure determined by single crystal X-ray diffraction techniques. It crystallizes in the monoclinic system with the cell parameters a = 7. 581(5) angstrom, b = 20.379(2) angstrom, c = 10.406(2) angstrom, beta = 98.30(3)-degrees, the space group is P2(1)/n and there are four mole cules per unit cell. There are intramolecular hydrogen bonds which ten d to keep the molecule planar and the adjacent molecules are linked by Van der Waals forces. The results indicate that the molecules of CI P igment Yellow 5 are introduced into the lattice of CI Pigment Yellow 1 and replace some molecules of it at random to form a solid solution w ith the crystal packing of CI Pigment Yellow 1 as a worthy crystal pac king, although the amount of CI Pigment Yellow 1 is 20% less than that of CI Pigment Yellow 5. Some crystal structures of related pigments h ave been compared; it is also concluded that the solid solution is iso morphous with CI Pigment Yellow 1 and Hansa Yellow 6G.