The effects of auxiliaries on turbidity of prepared dispersions are also investigated. Figure 4 demonstrates that the dispersion (3) containing dispersing and wetting agent alongside dextrin has the highest turbidity among other dispersions (1, 2, 4, and 5). The results show that the dispersion without dispersing agents have deposited after 2 hours while the dispersions containing dispersing agents have not considerably deposited after 24 hours. The obtained results confirmed that the stability of prepared
dispersions is enhanced by adding dispersing agents. Also, in these formulations, the presence of dextrin in the dispersion leads to increasing the stability and turbidity. The rate of deposition for the prepared dispersion without dispersing agents (dispersion 5) and containing dispersing and wetting agents with dextrin (dispersion 3) is very fast and slow, respectively. This finding demonstrates that the dispersion (3) has the most stability compared to dispersions (1, 2, 4, and 5). This can be attributed to b-cyclodextrin has a truncated cone shape and the cavity of b-cyclodextrin narrows towards the end, they give rise to a selective formation of inclusion complexes only with compounds having a molecular size complementary to the cavity dimensions. No covalent bond is established between b-cyclodextrin and disperse dye molecule and so the dissociation– association equilibrium in solution becomes one of the most characteristic features of the b-cyclodextrin-disperse dye association.[31]