Mixtures of sodium silicate (water glass) and low concentrated sulfuric acid form nano-sized silica particles. At high enough concentrations, these particles aggregate to a system spanning gel network. We studied the influences of the finite solubility of silica at high pH on the mechanical properties of this gel. Direct preparation of the sample in the Couette rheometer cell avoided any pre-shear of the gel structure that might arise from the filling of the rheometer. Time dependent measurements revealed that the storage modulus had a logarithmic time dependence. Frequency dependent measurements with classical and piezo rheometers revealed similarities of this chemically formed gels to physical gels. A frequency dependence of the storage modulus at the frequency typically below 6 rad/s was seen. We attribute this as a sign of structural relaxation due to the finite solubility of silica at high pH, which is also compatible with the logarithmic time dependence of the storage modulus. The reaction equilibrium between formation of bonds and the dissolution of bonds leads to the physical gel behavior of the system, which evolves through temporary bonds. The frequency dependence was more pronounced for lower water concentrations, higher temperatures and shorter reaction times. With two relaxation models (the modified Cole-Cole model and the empirical Baumgaertel-Schausberger-Winter model) we deduced characteristic times from the experimental data. Both models quantitative described the data and resulted in similar relaxation times.