Silicate solution

This is an acid-base reaction, in which the base is the oxide ion (p. 89) the acidic oxide SiOj displaces the weaker acidic oxide CO2 in the fused mixture. But in aqueous solution, where the 0 ion cannot function as a strong basefp. 89),carbon dioxide displaces silica, which, therefore, precipitates when the gas is passed through the aqueous silicate solution. In a fused mixture of silica and a nitrate or phosphate, the silica again displaces the weaker acidic oxides N2O5 and P4OJ0 ... 

Fig. 5. Viscosities of sodium silicate solutions vs percent solids A, ratio of 3.22 B, 2.4 C, 2.0 D, 1.6 and (-----), NaOH. To convert Pa-s to poise, divide...

Silicate Grouts. Sodium silicate [1344-09-8] h.3.s been most commonly used in the United States. Its properties include specific gravity, 1.40 viscosity, 206 mPa-s(=cP) at 20°C Si02 Na20 = 3.22. Reaction of sodium silicate solutions with acids, polyvalent cations, such organic compounds as formamide, or their mixtures, can lead to gel formation at rates, which depend on the quantity of acid or other reagent(s) used. 

In the Shoe or one-shot method (4), formamide is used to coagulate sodium silicate. The silicate solution used in the Joosten method can be diluted with water to lower its viscosity. Concentrations of sodium silicate between 10—70% are used (viscosities of 2.5—50 mPa-s). Concentrations of formamide are between 2 and 30%. Other reactants such as CaCl2 and sodium aluminate are used in concentrations between 2.4—12 g/L of silicate solution. 

It is advisable to saturate all corks with sodium silicate solution after fitting and boring them (p. 3, Note i). They are then covered with lead foil, wired in, and coated with shellac. 

Sodium silicate solution [1344-09-8] pKj 9.51, pKj 11.77 (for silicic acid, H4Si04) Purified by contact filtration with activated charcoal. 

Potassium silicate solutions are equally complex for example, an aqueous solution prepared from KOH and Si02 in which the ratio K Si is 1 1 contains 22 different discrete silicate anions as identified by Si COSY nmr studies. 

Silica gel is prepared in two stages. Firstly, an intimate mixture of sand and sodium carbonate are heated together in iron pans forming sodium silicate with the release of carbon dioxide. The sodium silicate is leached out of the cooled mixture, unreacted sand removed by filtration, and the resulting silicate solution treated with hydrochloric or sulfuric acid. 

Andersson, K. R., Dent Glasser, L. S. Smith, D. (1982). Polymerization and colloid formation in silicate solutions. In Falcone, J. G. (ed.) Soluble Silicates. ACS Symposium Series No. 194, Chapter 8. Washington, DC American Chemical Society. 

When a sodium silicate solution is acidified condensation reactions occur. Firstly, silanol... 

Prepared by precipitation from a mixture of magnesium sulfate and sodium silicate solutions and calcined at about 1200 °C. 

Silica gel. Silica gel is a porous amorphous form of silica (Si02) and is manufactured by acid treatment of sodium silicate solution and then dried. The silica gel surface has an affinity for water and organic material. It is primarily used to dehydrate gases and liquids. 

The transfer to the retort must be made before the mixture solidifies. The best method of closing the tubulure of the retort (unless this consists of Pyrex glass) is by means of a glass stopper too small for the hole and wrapped with asbestos paper moistened with sodium silicate solution. 

Coradin, T., Coupe, A. and Livage, J. (2003) Interactions of bovine serum albumin and lysozyme with sodium silicate solutions. Cdloids and Surfaces B-Biointerfaces, 29, 189-196. 

Oyane, A., Kawashita, M., Nakanishi, K, Kokubo,T., Minoda, M., Miyamoto, T. and Nakamura, T. (2003) Bonelike apatite formation on ethylene-vinyl alcohol copolymer modified with silane coupling agent and calcium silicate solutions. Biomaterials, 24, 1729-1735. 

The initial transition of dissolved silicate molecules into solid nanoparticles is perhaps the least explored step in the synthesis of zeolites. One impediment to understanding this mysterious step is the poorly elucidated molecular composition of dissolved particles. The major mechanistic ideas for the formation of zeolites approach these structures differently i) many researchers believe that secondary building units (SBU) must be present to form initial nanoslabs [1,2] ii) some others prioritize the role of monomers to feed artificially introduced crystal nuclei or assume that even these nuclei form via appropriate aggregation of monomers [3] iii) silicate solutions are also frequently viewed as random mixtures of various siloxane polymers which condense first into an irregular gel configuration which can rearrange subsequently into a desired crystal nucleus at appropriate conditions [4,5],... 

IR and Raman spectroscopy can fulfill these requirements and they are also robust enough for in situ silicate analysis in plant reactors [7]. Both of these techniques have been used for identifying the symmetric (s) and asymmetric (as), stretching (va, vas) and bending (5a, 5as) O-Si-O vibrations in aqueous alkaline silicate solutions which are the cheapest hence most frequently used ingredients for zeolite synthesis [8, 9 and references herein]. However, this information has to be "translated" into siloxane ring... 

About one decade ago Bass et al. [13,14] proposed first that such approach could help in exploring the structure of water dissolved silicates. Following this initiative, recently we critically evaluated how the published FTIR and Raman assignments could be adopted for differentiating between the molecular structures of some commercially available sodium silicate solutions [7-9,15], In this paper we present comparative structural studies on aqueous lithium and potassium silicate solutions as well. According to some NMR studies, the nature of A+ alkaline ion and the A+/Si ratio barely affects the structural composition of dissolved silicate molecules [5], In contrast, various empirical observations like the tendency of K-silicate solutions to be less tacky and more viscous than their Na-silicate counterparts, the low solubility of silica films obtained from Li-silicate solutions compared to those made from other alkaline silicate solutions, or the dependence of some zeolite structures on the nature of A+ ions in the synthesis mixture hint on likely structural differences [16,17]. It will be shown that vibrational spectroscopy can indeed detect such differences. 

Table 1. Selected properties of the initial alkaline silicate solutions (more at www.pqcorp.com)...

Table 2. Concentration, dissociation, ion size and other parameters of aqueous alkaline silicate solutions... 

Dissociation constant of silicic acid calculated according to the a + = [(Kacx Kw)/c]1/2fbrmula for dissociation of salts formed from weak acid and strong base a+ is the activity of protons (from pH), K w is the ionization constant of water, and c is the concentration of silicate solution. 

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