Although silicon is a constituent of normal animal tissues, silicic acid formed by the dissolution of inhaled quartz particles can induce the formation of pathological lesions in which the normal tissue is replaced by fibrotic tissue arranged concentrically around the silica particles. The mechanism of the change which constitutes the disease, silicosis, is unknown. Schulman & Rideal (1937) dem...

in this study, alkaline colloidal silica was prepared by titration of an alkaline solution such as sodium silicate with silicic acid in constant range of ph  .this constant range of ph was achieved by using concentrated soduim silicate solutions as ph adjusting solutions during titration.the sodium silicate solutions  having a variety of concentrations were passed  through ion-exchange resin to...

A main concern about cement materials for the construction of the repository is altering the groundwater to high alkalinity around the repository. Under such chemical condition, the behavior of the silicic acid is one of the key factors to estimate the initial condition of the repository system after the backfill. Since the solubility of silicic acid is extremely large in pH larger than 10, the...

Silicon (Si) is the most abundant element present in the Earth's crust besides oxygen. However, the exact biological roles of silicon remain unknown. Moreover, the ortho-silicic acid (H4SiO4), as a major form of bioavailable silicon for both humans and animals, has not been given adequate attention so far. Silicon has already been associated with bone mineralization, collagen synthesis, skin, h...

In this study, alkaline colloidal silica was prepared by titration of an alkaline solution such as sodium silicate with silicic acid in constant range of pH  .This constant range of pH was achieved by using concentrated soduim silicate solutions as pH adjusting solutions during titration.The sodium silicate solutions  having a variety of...

[1] Studies invoking the silicic acid leakage hypothesis to explain events of high biogenic opal deposition at low latitudes did not consider variations in formation rate of Southern Ocean intermediate waters. Comparison of dSi records from the Southern Ocean to records of biogenic opal accumulation from low-latitude upwelling systems indicates a strong negative correlation between the silicic ...

[1] Observations of silicic acid and nitrate along the lower branch of the global conveyor belt circulation show that silicic acid accumulation by diatom opal dissolution occurs at 6.4 times the rate of nitrate addition by organic matter remineralization. The export of opal and organic matter from the surface ocean occurs at a Si:N mole ratio that is much smaller than this almost everywhere (cf...

This article reports the inhibitory effects of phosphonated chitosan (PCH, synthesized from chitosan (CHS) by a Mannich-type reaction) on the in vitro silicic acid condensation. In particular, the ability of PCH to retard silicic acid condensation in aqueous supersaturated solutions at circumneutral pH is studied. Furthermore, the effect of anionic carboxymethyl inulin (CMI) polyelectrolyte on ...

Diatoms are an important group of eukaryotic algae with a curious evolutionary innovation: they sheath themselves in a cell wall made largely of silica. The cellular machinery responsible for silicification includes a family of membrane permeases that recognize and actively transport the soluble precursor of biosilica, silicic acid. However, the molecular basis of silicic acid transport remains...

Sandy sediments of tidal beaches are poor in reactive substances because they are regularly flushed by significant flow caused by tidal forcing. This transport process may significantly affect the flux of reactive solutes to the ocean. A two dimensional model coupling the Richards equation that describes the flow in permeable sediments and the conservation equation of the silicic acid was devel...