Water-Soluble Silicates

Vail s two-volume monograph on soluble silicates (1) after a quarter of a century is still the primary source of technical and industrial information. It is pertinent to review some of the advances made since then in the chemistry of soluble silicates, from which silica colloids and gels are largely derived. 

On the other hand, when it was learned how to make silica particles of different sizes it was found that smaller particles could be stabilized as sols by adding more alkali. Thus 5 mm particles were stabilized with a ratio of 25 1. However, attempts to obtain concentrated solutions with still smaller particles and lower ratios of 25 1 to 4 1 led to gelled mixtures when sodium hydroxide was used as the alkali. Then it was found that such solutions could be made using other alkalis so that solutions containing particles smaller than 5 nm, on down to molecular dimensions, were obtained. 

Solutions in this range are referred to here as polysilicates, with the understanding that these polyanions may at the same time be treated as very small charged particles. 

Over the past 50 years there have been major changes in theories of the nature of the silica in the conventional alkali silicate solutions with Si0j Na20 ratios from 2 1 to 4 1. The physical similarity of viscous, stringy solutions of soluble silicates to solutions of linear organic polymers led in some cases to the supposition that vis- 

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Since the use of alcohol in the sol-gel process can lead to aggregation of the colloidal metal, Au/SiC>2 catalysts have been prepared without alcoholic solution, using tetramethyl orthosilicate (TMOS) as a water-soluble silicic precursor and colloidal gold by reducing aqueous HAuCLi with magnesium citrate.114 However, the size of the gold particles was not reported, but reduction by citrate ion does not usually produce small particles. 

The derivatization with sodium molybdate can also be utilized for the analysis of water soluble silicate. Its separation can be achieved with both ion-exchange and ion-exclusion chromatography. Silicate with sodium molybdate also forms the yellow heteropolyacid H4[Si(Mo3O10)4] with an absorption maximum at 410 nm. 

S.S. Kim, T.R. Pauly, and T.J. Pinnavaia, Non-ionic Surfactant Assembly of Wormhold Silica Molecular Sieves from Water Soluble Silicates. Chem. Commun., 2000, 835-836. 

An important and often overlooked aspect of complicated solution chemistry of salts other than inert electrolytes is fomiation of water soluble complex species involving products of dissolution of sparingly soluble materials (adsorbents). For instance, indirect spectroscopic evidence has been presented [1] that a silicate complex is the dominating soluble species of Eu (total Eu concentration of 10 mol dm ) in the presence of silicates (2.7x 10 mol Si dm ) over the pH range 6-8. The solubility of silica is about 10 mol dm, thus, water soluble silicate complexes can play an important role in the partition of Eu (and other trivalent lanthanides) between aqueous solution and silica. 

This new nanostructured binder was obtained by laminar mixing of the liquid glass containing alkali metal cations as Na, TFS, and a water-soluble silicate, containing an organic alkaline cation (WSS) such as l,8-diazabicycloundecene-7 (DBUS, Structure 7.1) or l,5-diazabicyclononene-5 (DBNS, Structure 7.2). 

Water-soluble silicate, containing an organic alkaline cation, can be obtained by interaction of quaternary organic ammonium base salts and amorphous silica. The relationship of Si02 to the organic base is 1.65 1 for DBUS and 2.0 1 for DBNS. It should be noted that the soluble organic alkali silicates, for example, tetrabutylam-monium silicate (TBAS) is also used as a component of self-extinction binder. 

Water-soluble silicate, containing an organic alkaline caution... 

After alcohol removal, fusion of the sample cleaves all organic groups from silicon, converting silanolate to water-soluble silicates. 

Amorphous silicates are considered safe additions to foods, and therefore their use as anticaking agents, for example, is permitted in amounts up to 2% by weight. Water-soluble silicates are also of low toxicity studies of the effects of feeding various silicon compounds to laboratory animals have generally shown the substances to be innocuous under the test conditions. Likewise, the available data on orally administered silicates in humans substantiate the biological inertness of these compounds (Carlisle 1997). 

Structure of Water Soluble Silicates with Complex Cations... 

B. Vlnot, R. S. Schecter, and L, W. Lake, Formations of Water-Soluble Silicate Gels by the Hydrolysis of a Dlester of Dicarboxylic Acid Solubilized as Mlcroemulslons, Paper SPE 14236, Presented at the 60th Annual Technical Conference and Exhibition of the SPE, Las Vegas, NV, Sept. 22-25 (1985),... 

Hydrated water-soluble silicates are also known as hydrous polysUicates or dried silicate solutions. The most common soluble silicates are sodium silicates [19]. 

Sodium silicate is only common water soluble silicate. 

Why are most silicates water insoluble Name a water soluble silicate. 

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