  A lyotropic chromonic liquid crystal (LCLC) is an orientationally ordered
system made by self-assembled aggregates of charged organic molecules in water,
bound by weak non-covalent attractive forces and stabilized by electrostatic
repulsions. We determine how the ionic content of the LCLC, namely the presence
of mono- and divalent salts and pH enhancing agent, alter the viscoelastic
properties of the LCLC. Aqueous solutions of the dye Sunset Yellow with a
uniaxial nematic order are used as an example. By applying a magnetic field to
impose orientational deformations, we measure the splay $K_1$, twist $K_2$ and
bend $K_3$ elastic constants and rotation viscosity $\gamma_1$ as a function of
concentration of additives. The data indicate that the viscoelastic parameters
are influenced by ionic content in dramatic and versatile ways. For example,
the monovalent salt NaCl decreases $K_3$ and $K_2$ and increases $\gamma_1$,
while an elevated pH decreases all the parameters. We attribute these features
to the ion-induced changes in length and flexibility of building units of LCLC,
the chromonic aggregates, a property not found in conventional thermotropic and
lyotropic liquid crystals formed by covalently bound units of fixed length.
