Showing papers on "Silica gel published in 1968"
422 citations
255 citations
TL;DR: In this paper, supported platinum consisting of 15-A crystallites has been prepared by reduction of platinum ammine ions adsorbed on the surface of silica gel, which has been carried out by hydrogen chemisorption, X-ray diffraction, and electron microscope techniques.
187 citations
TL;DR: Approximate applicability of the procedure for quantitative analyses of tissue lipids is demonstrated on lipid extracted from rat livers.
173 citations
Patent•
06 Aug 1968
TL;DR: In this paper, the process of preparing silica gels directly from water, comprising critically controlled steps of precipitation of the silica gel, heat aging the precipitated silica hydrogel slurry, washing the aged product with solutions of salts having a displacing effect on sodium, disintegrating the gel and freeze drying the hydrogels so as to remove substantially all of the water.
Abstract: Silica gels having narrow pore diameter distribution in the range of 300-600 A and surface areas in the range from 200-500 m.2/g., and the process of preparing such silica gels directly from water, comprising critically controlled steps of precipitation of the silica gel, heat aging the precipitated silica hydrogel slurry, washing the aged product with solutions of salts having a displacing effect on sodium, disintegrating the gel and freeze drying the hydrogel so as to remove substantially all of the water i.e., vacuum subliming the water from the gel after freezing said hydrogel particles at a temperature sufficient to maintain the water in the pores in the frozen state.
112 citations
TL;DR: The use of a stable solution of ferric chloride for the detection of cholesterol and cholesteryl esters on thin-layer chromatographic layers is described and the levels of sensitivity for the new reagent are shown.
99 citations
TL;DR: In this article, a new method based upon chromatography was used to measure surface diffusion coefficients for ethane, propane, and n-butane on silica gel, which correspond to very low surface coverages (fraction of a monolayer of the order of 10−4).
Abstract: A new method, based upon chromatography, was used to measure surface diffusion coefficients for ethane, propane, and n-butane on silica gel. The diffusivities correspond to very low surface coverages (fraction of a monolayer of the order of 10−4) and hence should represent limiting values. A survey of available surface diffusion information, all at higher coverages, indicated that the results reported here are at the lower end of the range of diffusivities. The activation energy and heat of adsorption, for example, for n-butane, were 4.4 and −7.8 k cal./mole, respectively.
Surface diffusion was a significant fraction of the total intraparticle mass transport, in part because in the small pores in silica gel gas phase diffusion was solely by the Knudsen mechanism. For propane, surface migration was 73% of the total transport at 50°C. and 61.5% at 125°C.
99 citations
TL;DR: Factors which influence separation of carbohydrates on silica gel impregnated with boric acid, and the limitations if the monodimensional technique are investigated are investigated and discussed.
68 citations
TL;DR: The major complement-fixing antigen of Mycoplasma pneumoniae is found in the lipid fraction of the organism and it was demonstrated that fraction D did contain multiple components, all but one of which were carbohydrate-containing lipids (giving positive reactions when sprayed with orcinol-sulfuric acid reagent).
Abstract: The major complement-fixing antigen of Mycoplasma pneumoniae is found in the lipid fraction of the organism. When the lipids of M. pneumoniae were fractionated by column chromatography on silicic acid, serological activity against both rabbit and human immune sera was found in two fractions, B and D. Fraction B, eluted with chloroform–methanol (9:1), was a minor component in terms of total complement-fixing activity and contained a complex of lipids which were detected in the region characteristic of phosphatidic acids by thin-layer chromatography on Silica Gel G. Fraction D, eluted with ethyl acetate–methanol (3.5:2), had approximately the same complement-fixing antigen titer as the original lipid extract and appeared as a “comet-shaped” spot between phosphatidylethanolamine and phosphatidylcholine on Silica Gel G plates charred with sulfuric acid. However, by thin-layer chromatography on Silica Gel H impregnated with sodium tetraborate, it was demonstrated that fraction D did contain multiple components, all but one of which were carbohydrate-containing lipids (giving positive reactions when sprayed with orcinol-sulfuric acid reagent). Fraction D was found to contain glycerol and phosphate in equimolar ratios but did not contain nitrogen. Two sugars were detected which migrated on paper chromatograms with glucose and galactose. Images
46 citations
01 Aug 1968
TL;DR: The rate data indicate a physical type adsorption of 2,4-dichlorophenoxy acetic acid on some mineral surfaces such as clays, silica gel, sand, alumina, and humic acid, and the rate constant varies from 10−3 to 10−5 sec−1 depending on the surface.
Abstract: A detailed equilibrium and kinetic study of the adsorption of 2,4-dichlorophenoxy acetic acid (2,4-D) on some mineral surfaces such as clays, silica gel, sand, alumina, and humic acid has been made. The equilibrium data have been explained with the Freundlich type isotherm, and a fit of the kinetic data with a theory proposed by Fava and Eyring was tried. The heat of adsorption as a function of surface coverage has been calculated. The heat of adsorption changes exponentially with the amount of 2,4-D sorbed. In most cases the heat changes are small, but the heat changes for silica gel and sand are larger compared to other surfaces. This has been discussed in the light of weak hydrogen bonding between 2,4-D and the surface material. Humic acid and illite adsorb more 2,4-D than other surfaces. The rate constant varies from 10−3 to 10−5 sec−1 depending on the surface. The activation energy in most of the cases is almost negligible. The rate data indicate a physical type adsorption.
43 citations
TL;DR: In this paper, the authors have grown cuprous chloride in silica gel using a system including large reservoirs and allowing for easy removal of the complete gel volume Clear, tetrahedral CuCl crystals larger than 6 mm on an edge have been produced Evaluation of the conditions in the gel has also been made by chemical analysis of the gels both as a function of distance from the gel solution interface and of time Concentration gradients and degree of saturation.
TL;DR: The isolation and characterization of disialyllactose (N- acetylneuraminyl-(2 → 8)-N-acetylneURaminyl(2 → 3)-galactopyranosyl-(1 → 4)-glucopyranoide) is described.
TL;DR: Cardanol, the main constituent of technical cardanol, has been successfully separated into four components, viz. saturated, mono- di-, and tri-olefins using silver nitrate impregnated silic gel, thin-layer and column chromatographic techniques.
TL;DR: In this paper, the infra-red spectra of constitutional and terminal hydroxyl groups of biotite, muscovite, silica gel, alumina and decationated Y-zeolite were measured between room temperature and 600°.
Abstract: The infra-red spectra of constitutional and terminal hydroxyl groups of biotite, muscovite, silica gel, alumina, silica-alumina and decationated Y-zeolite were measured between room temperature and 600°. Large changes in optical density and band half-width were sometimes observed. However, the integrated intensities showed little change with silica and silica-alumina and decreased by approximately 15% with the others. Although these latter results are not conclusive evidence for proton delocalization, they can be interpreted in this way.
LGC1
TL;DR: In an uncertified cement, H2PO 4 -1 ions were found in substantial amounts even in the set cement, which accounted for poor strength and durability.
Abstract: Infrared studies have shown that silica gel and H2PO4-1 ions are formed in fresh cement paste. Subsequently, during setting and hardening, H 2PO4-1 ions further react to form covalent phosphates and are removed from the system. In an uncertified cement, H2PO 4-1 ions were found in substantial amounts even in the set cement, which accounted for poor strength and durability.
TL;DR: In this article, the 60Co γ-radiolysis of N2O adsorbed on silica gel and zirconia has been studied and shown that a large fraction of the energy absorbed in the solid is able to cause decomposition of the n2O.
Abstract: The 60Co γ-radiolysis of N2O adsorbed on silica gel and zirconia has been studied. In both systems a large fraction of the energy absorbed in the solid is able to cause decomposition of the N2O. Fo...
TL;DR: In this article, a thin-layer chromatographic analytical procedure was used to detect the lower, unsaturated and higher fatty acids, with which the lower and unsaturated acids were successively detected.
Patent•
18 Jun 1968TL;DR: In this paper, an aqueous alkali metal silicate solution is partially neutralized with a mineral acid until a pH of about 9.6-10.9 is reached.
Abstract: An aqueous alkali metal silicate solution is partially neutralized with a mineral acid until a pH of about 9.6-10.9 is reached. When a soft gel has formed, the mixture is vigorously agitated to obtain a fine slurry, and more mineral acid is added until a pH of about 0.5-3.0 is reached. The resultant slurry is then spray dried and washed. After drying at about 200* C., product particles of desiccant silica gel having average particle sizes ranging from 10 to 100 microns, a surface area of about 650-950 m.2/g., and a pore volume of 0.35-0.8 cc./g. are obtained.
TL;DR: A method for fingerprinting two protein samples on thin layers of silica simultaneously and under identical conditions is described and is applicable to quantities of protein of 100–200 μg.
TL;DR: In this paper, a simple method for specific surface determination of silica gels is developed on the basis of the sorption of Zn(en)3++, which is independent of the pH value and of the value of the specific surface and the mode of preparation of the Sorbent used.
TL;DR: In this paper, it has been established that when there is an insufficient number of oxide units per hydrophobe the color intensity is markedly diminished, and with smaller numbers of oxides the color fails to form altogether.
Abstract: Cobalt thiocyanate is used as a colorimetric reagent to determine traces of polyoxyethylene nonionic surfactants. It has been established that when there is an insufficient number of oxide units per hydrophobe the color intensity is markedly diminished, and with smaller numbers of oxide units the color fails to form altogether. the exact number of oxide units at which the colorimetric procedure fails has not been established previously, due to the unavailability of the pure individual ethylene oxide adducts. The individual ethylene oxide adducts of high purity were obtained by liquid chromatography on silica gel. The mixed solvent used was originally developed for thin-layer chromatography and was applied without change to column chromatography. The composition of the separated isomers has been determined by infrared, ultraviolet, nuclear magnetic resonance, and mass spectroscopy. The apparent molar absorption coefficients have been obtained for the individual cobalt thiocyanate complexes both in benzene and chlorform. For the low molecular weight adducts studied, the efficiency of color development and extraction into the organic phase has been found to be dependent on the concentration of the cobalt thiocyanate reagent. A saturated aqueous solution of cobalt thiocyanate was found to be preferable and benzene was found to be a more reliable extractant than chloroform. The apparent molar absorption coefficients do not vary linearly with chain length at low molecular weights and the minimum number of ethylene oxide units that will form an extractable color with the saturated reagent was found to be 3.
TL;DR: In this article, a simple technique for the fractionation of complex flavour mixtures by liquid chromatography on silica gel using low boiling solvents at 10.5°C was described.
TL;DR: Solvent systems consisting of n-propanol: n-butanol: NH4OH: H2O—4:4:1:1 on silica gel G plates were found to be the most effective and resolved impurities in commercial dyes.
Abstract: Thin-layer chromatography will resolve impurities in commercial dyes, and will do so much faster than paper chromatography. Solvent systems consisting of (a) n-propanol: n-butanol: NH4OH (conc.): H2O—4:4:1:1; (b) n-propanol: NH4OH (conc.): H2O—8:1:1 on silica gel G plates; and (c) n-propanol: NH4OH (conc.): H2O-7:2:1 on Adsorbosil plates were found to be the most effective. Dyes studied were azure A, azure B, azure C, methylene blue, toluidine blue O, thionin, pyronin B, pyronin Y, methyl green, crystal violet amido black 10B and buffalo black (NBR).
TL;DR: An assay procedure for phenylbutazone involving acid and base shake-out followed by UV spectrophotometric measurement at 264 and 232 mμ is described, which enables potentially interfering substances such as other medicaments, excipients, and dyes to be removed, and the quantities of phenyl butazone and its decomposition products to be determined.
TL;DR: Pigments inseparable in the above systems are separated: free violins and verdins on polyamide TLC with methanol-10% ammonia-water, esterified urobilin and stercobilin on Silica Gel G with chloroform-ethanol.
TL;DR: The lecithins of rat liver are resolved into three fractions by chromatography on a thin layer of silica gel impregnated with silver nitrate.