Silicic Acid Solution Research Articles

Polymerisation of the silicate anion in acidic solutions. Gelation and trimethylsilylation studies

Trimethylsilylation studies on silicic acid solutions, produced by hydrolysis of tetramethoxysilane, show that gel time is independent of the rate of disappearance of monomeric silicic acid.

Toroidal microporous silica gel

Microporous amorphous silica gel with a characteristic toroidal form of the elementary particles, has been prepared by thermal dissociation of a solution of silicic acid in a spray dryer. The substance obtained was investigated by electron microscopy, infra-red spectroscopy and thermal analysis. The adsorption properties were studied by lowtemperature adsorption of nitrogen.

Gas chromatography of trimethylsilylated silicate anions : separation with glass capillary columns and new aspects in derivatization

Abstract The advantages of capillary-column gas chromatography (GC) in the analysis of trimethylsilylated silicate systems are demonstrated and separation parameters and measurement and calculation methods for the qualitative and quantitative analysis of different silicic acid solutions are outlined. The problems of the trimethylsilylation procedures are discussed. Results obtained by GC after derivatization with bistrimethylsilylacetamide (BSA) as the trimethylsilylating agent indicate that both the unwanted condensation and hydrolysis during silylation are suppressed if the proton-trimethylsilyl is accelerated e.g. , by a powerful trimethylsilyl donor such as BSA, and if the pH of the silylation reaction mixture is controlled. Chromatograms of some silicic acid samples are compared with those of identical samples silylated according to Lentz and Gotz-Masson, respectively. Comparison of both the qualitative and quantitative results indicates that the compositions of the original silicic acid solutions are best reflected in the chromatograms after silylation with BSA. The effect of the after-treatment of the silylated silicic acid solution with Amberlyst 15 cation-exchange resin is disscussed separately.

Gas Chromatography of trimethylsilylated silicate anions : Separation with glass capillary columns and new aspects in derivatization

The advantages of capillary-column gas chromatography (GC) in the analysis of trimethylsilylated silicate systems are demonstrated and separation parameters and measurement and calculation methods for the qualitative and quantitative analysis of different silicic acid solutions are outlined. The problems of the trimethylsilylation procedures are discussed. Results obtained by GC after derivatization with bistrimethylsilylacetamide (BSA) as the trimethylsilylating agent indicate that both the unwanted condensation and hydrolysis during silylation are suppressed if the proton-trimethylsilyl is accelerated e.g., by a powerful trimethylsilyl donor such as BSA, and if the pH of the silylation reaction mixture is controlled. Chromatograms of some silicic acid samples are compared with those of identical samples silylated according to Lentz and Götz-Masson, respectively. Comparison of both the qualitative and quantitative results indicates that the compositions of the original silicic acid solutions are best reflected in the chromatograms after silylation with BSA. The effect of the after-treatment of the silylated silicic acid solution with Amberlyst 15 cation-exchange resin is disscussed separately.

Interaction of Monomeric Silicic Acid With Copper and Zinc and Chemical Changes of the Precipitates With Aging

AbstractPrecipitates were formed by titrating dilute, acidic solutions of monomeric silicic acid [Si(OH)4] and copper (Cu) or zinc (Zn) to various pH values. Those containing Cu formed above pH 6.0; those containing Zn formed above pH 7.0. Periodically, during 2 years of aging in their mother liquor, the liquid phase was sampled and analyzed and the Cu/Si or Zn/Si molar ratios of the precipitates calculated. The Cu/Si ratios of those containing Cu stabilized readily near 0.78 and were unaffected by pH. The Zn/Si ratios of the Zn‐containing precipitates, however, changed as a result of Si enrichment from near 1.80 soon after their formation to near 0.80 after aging 2 years. The systems with the lowest pH changed first and most rapidly and became stabilized within 6 months; those above pH 8.0 changed more slowly.The Zn‐containing precipitates gave diffuse X‐ray diffraction patterns indicative of a 2:1 layer silicate, whereas those containing Cu were amorphous.

Equivalence of Anomalous Water and Silicic Acid Solutions

CHERKIN1 has again drawn attention to the possibility that a glass leaching process may be a satisfactory explanation for the formation of “anomalous” water. One of the chief pieces of evidence advanced in support of this interpretation is observation of the formation of residues following evaporation of “anomalous” water1. These residues are described by some workers as being solid material2 and by others as having the properties of a gel3. They do not seem so far to have been systematically studied. We have now carefully investigated the formation and principal characteristics of the residue and have found that it is possible to prepare, without the intermediary of finely drawn capillaries, a silica solution which possesses most of the features commonly associated with “anomalous” water.

Stability of hectorite in weakly acidic solutions. III. Adsorption of heavy metal cations and hectorite solubility

AbstractThe heavy metal cations studied were adsorbed by hectorite suspended in 0.05 M calcium chloride as a pH-dependent reaction in the order, Cu > Zn > (Co, Mn) > Ni. The adsorption of heavy metal cations was accompanied by the removal from solution of silicic acid released by clay dissolution. It is proposed that the reaction takes place on edge surfaces such that the clay lattice is effectively extended. This result complements other work in which it has been shown that the adsorption of silicic acid by other silicate clays results in an increased adsorption of zinc, cobalt and nickel. The present study did not provide evidence of the exchange of zinc and other cations for lattice magnesium.The solubility of hectorite was decreased in the presence of heavy metal cations in the same order that favoured their adsorption. It is proposed that they limit the dissolution of hectorite in weakly acidic solutions by adsorption on or near the sites most prone to proton attack, that is, the magnesium ions of the octahedral layer exposed at edges and defects.

The solubility of potassium from soil illites. II. Mechanisms of potassium release

The release of potassium from four soil clays containing illites of different degrees of degradation was found to be independent of the solution of silicic acid or aluminium from the clay minerals. The lattice potassium is released into solution by a displacement reaction. The displacement of potassium by calcium ions is dependent on the prior release of one lattice potassium by one hydrogen ion, presumably because the entry of the hydrogen ion makes the potassium at neighbouring sites in the lattice accessible to other cations. The reaction may be written as 7Ks+ + H+ + 3Ca2+ 7K+ + 3CaS2+, where the subscript S refers to the solid (clay) phase. At pH values above pH 11, potassium is released by breakdown of the mineral structure by the action of hydroxyl ions.

Optimum conditions for the colorimetric microdetermination of silicon

The best conditions for the formation ofβ-silicomolybdic acid and its reduction to molybdenum blue, in the presence of phosphate, iron and some other interfering substances have been critically investigated to ascertain the most suitable method for the precise colorimetric micro-determination of silicon in biological material and minerals. The method ofKing andStacy was modified by lowering the initial and increasing the final concentration of sulphuric acid, by securing the same electrolyte concentration in sample and standard and by lengthening the time allowed for reduction of theβ-silicomolybdic acid. These improvements diminish the interfering effect of phosphate and iron and stabilise the molybdenum blue colour. The proposed method permits determination of 20–50 μg SiO2 in the presence of up to 4.5 mg of phosphate and 3 mg of iron, with an accuracy of about ±1 μg of SiO2. Alkali fusion was found to be the most suitable way to produce the monomeric silicic acid solutions necessary for the determination. A detailed method for determination of silica in tissues and minerals is described, and some results are given.

The solubility of silicic acid in salt solutions

1. The solubility of silicic acid in solutions of salts has been studied; it has been shown that only high salt concentrations substantially lower it. 2. The nature of the anion affects the solubility of silicic acid more strongly than the nature of the cation; the chloride and nitrate ions have the greatest effect; the effect of the cation under otherwise similar conditions increases with an increase in its charge. 3. The addition of powdered quartz or calcined silica to a supersaturated solution of silicic acid does not cause the separation of silicic acid from the solution.

New method for determination of the activation energy for the gelation of silicic acid solutions

AbstractA new method for the determination of the activation energy for the setting of silicic acid solutions is described. Experimental results point to the conclusion that setting to a gel occurs at a definite stoichiometric point which is independent of temperature.

XIV. On the properties of silicic acid and other analogous colloidal substances

The prevalent notions respecting solubility have been derived chiefly from observations on crystalline salts, and are very imperfectly applicable to the ss of colloidal substances. Hydrated silicic acid, for instance, when in a soluble condition, is property, speaking a liquid body, like alcohol, scible with water in all proportions. We have no degrees of solubility speak of with respect to silicic acid, like the gelatinous condition, which is usually looked upon as destitute of solubility. The jelly of silicic acid may be more or less rich in combined water, as it is first pre-red, and it appears to be soluble in proportion to the extent of its hydragon. A jelly containing 1 per cent. of silicic acid, gives with cold water solution containing about 1 of silicic acid in 5000 water; a jelly con-ining 5 per cent. of silicic acid, gives a solution containing about 1 per acid in 10,000 water. A less hydrated jelly than the last mentioned still less soluble; and finally, when the jelly is rendered anhydrous, it ves gummy-looking white masses, which appear to be absolutely insoble, like the light dusty silicic acid obtained by drying a jelly charged with salts, in the ordinary analysis of a silicate. The liquidity of silicic acid is only affected by a change, which is permanent (namely, coagulation or pectization), by which the acid is converted into the gelatinous or pectous form, and loses its miscibility with water. The liquidity is permanent in proportion to the degree of dilution of silicic the contrary, by concentration, and by elevation of temperature. A liquid silicic acid of 10 or 12 per cent. pectizes spontaneously in a few hours at the ordinary temperature, and immediately when heated. A liquid of 5 per cent. may be preserved for five or six days; a liquid of 2 per sent. for two or three months; and a liquid of 1 per cent. or less are no doubt practically unalterable by time, and hence the possibility of soluble silicici acid existing in nature. I may add, however, that no solution, weak or strong, of silicic acid in water has shown any disposition to deposit crystals , but always appears on drying as a colloidal glassy hyalite. The formation of quartz crystals at a low temperature, of so frequent occurrence in nature, remains still a mystery. I can imagine that such crystals are formed at an inconceivably slow rate, and from solutions of silicic acid which are extremely dilute. Dilution no doubt weakens the colloidal character of substances, and may therefore allow their crystallizing tendency to gain ground and develope itself, particularly where the crystal once formed is completely insoluble, as with quartz.