Ammonium Alum Research Articles

Effect of ultrasonic waves on crystallization from a supersaturated solution of alum

The effect of ultrasonic waves on the particle size and distribution of precipitated crystals from a slowly cooled supersaturated solution of ammonium aluminium sulphate hydrate was investigated. It was found that ultrasonic irradiation greatly promoted the homogeneity in particle sizes of the crystals precipitated. Average particle sizes of both the mechanical stirred and the ultrasonically treated samples did not change much if the initial solute concentration was beyond the saturation solubility of the solution. The higher acoustic intensity of the higher frequency ultrasonic transducer resulted in a larger average particle size in the recrystallization process.

Thermal decomposition of basic aluminium ammonium sulphate in an environment of carbon and water vapour

By means of the thermogravimetric method, differential thermal analysis. X-ray diffraction phase analysis, infrared spectroscopy, electron microscopy and chemical analyses, stages of decomposition of basic aluminium ammonium sulphate (BAAS) in an environment of carbon and water vapour were studied. It has been found that the addition of carbon and water vapour influences the course of alunite decomposition only in the last stage, i.e. the desulphuration of the compound. This process occurs at a lower temperature than in air. The final product of decomposition of the basic salt at 1223 K is γ-Al 2O 3. The experimental work was preceded by the thermodynamic analysis of the desulphuration process of BAAS in an environment of carbon and water vapour, and the results have been correlated with experimental data.

Membrane fluidity of platelets and erythrocytes in patients with Alzheimer's disease and the effect of small amounts of aluminium on platelet and erythrocyte membranes.

The membrane fluidity of platelet and erythrocyte membranes in 10 Alzheimer's disease patients and 9 age-matched controls was studied. The platelet membranes of patients with Alzheimer's disease were found to be significantly more fluid than those of controls (p less than 0.02). However, erythrocyte membranes of Alzheimer patients were less fluid (more viscous) than those of controls (p less than 0.05). On further investigation of platelet and erythrocyte membranes obtained from healthy volunteers, the fluidity was found to change with increasing aluminium concentrations. When aluminium ammonium sulphate (0.01-10 microM) was added to membrane suspensions, the fluidity of platelet membranes was increased, whereas the fluidity of erythrocyte membranes was decreased (i.e. the microviscosity was increased).

Some physicochemical properties of aluminium oxides obtained from basic aluminium sulphates

Eight different kinds of aluminium oxide were obtained by thermal decomposition of isomorphous alunite compounds, namely, basic aluminium ammonium sulphate (BAAS) and basic aluminium potassium sulphate (BAPS). The thermal decomposition of the basic salts was performed in an atmosphere of air, in vacuum, in an atmosphere of hydrogen, and in an environment of carbon and water vapour. The Particle size distribution, phase composition, specific surface area (adsorption of benzene vapour), and the Na 2O and K 2O contents were determined in the aluminium oxide samples obtained.

Chorda tympani and lingual nerve responses to astringent compounds in rodents

A wide variety of compounds in foods and beverages produce astringent sensations when introduced into the oral cavity. There is controversy, however, whether “astringency,” with its associated puckering and drying sensations, is a fundamental taste quality or is a tactile sensation. To address this issue, electrophysiological recordings were made from the gerbil chorda tympani nerve and the rat lingual nerve. The chorda tympani nerve transmits taste information from the anterior 23 of the tongue, whereas the lingual nerve transmits tactile, thermal and pain sensations from the anterior 23 of the tongue. The astringent compounds tested were: tannic acid, tartaric acid, gallic acid, aluminum ammonium sulfate and aluminum potassium sulfate. Tannic acid, tartaric acid, and gallic acids were tested at concentrations up to 120 mM over a pH range from ∼2 to 6. The aluminum salts were tested at concentrations up to 160 mM only at low pH's. All compounds rapidly (and at lower concentration, reversibly) stimulate the chorda tympani nerve in a concentration-dependent manner at all pH's tested. The rapidity and reversibility of the chorda tympani responses suggest that astringent-tasting compounds interact directly with taste cells rather than indirectly by precipitating salivary proteins. At pH 6, tannic acid, tartaric acid, and gallic acid all elicit robust chorda tympani responses, implying that the ionized forms of these compounds produce taste sensations. None of these compounds stimulate lingual nerves over the same concentration and pH ranges used in the chorda tympani experiments. From these experiments it is concluded that: 1) to analyze responses produced in the oral cavity by astringent compounds, it is necessary to account for the responses of all ions in the stimulus solution, and 2) astringency is a taste quality in rodents.

Electrical properties of pure and doped ammonium alum

Pure ammonium alum, and Cr-doped and Fe-doped single crystals were prepared. The resistivity and pyrocurrent were measured as a function of temperature. The resistivity varies exponentially with temperature. The activation energy for all samples was calculated. At any temperature, the resistance increased with increase in Cr concentration and decreased with increase in Fe concentration.

On-line measurement of supersaturation during batch cooling crystallization of ammonium alum.

An electrical conductivity method was tested. The system of ammonium aluminum sulfate-water was used as a model system

Kinetics of thermal dissociation of basic aluminium ammonium sulfate in a hydrogen atmosphere

The rate of release of sulfur oxides from basic aluminium ammonium sulfate (BAAS) under isothermal, isobaric conditions in a hydrogen atmosphere was studied. Twomethods of selection of theg(α) function which best describes the isothermal experimental data are discussed. The first method is based on statistical criteria and the second one on the the use of a reduced-time scale. Kinetic parameters for the thermal decomposition of BAAS in a hydrogen atmosphere are reported.

Rapid Microscopic Detection of Malaria Parasites Permanently Fluorochrome Stained in Blood Smears with Aluminum and Morin

Intra- and extracellular Plasmodium parasites in fixed blood smears are easily identifiable by fluorescence microscopy after brief mordanting with aluminum ammonium sulfate and staining with morin (3,5,7,1',4'-pentahydroxyflavanol). The intensely fluorescent preparations of stained parasites are strongly resistant to photodegradation and remained essentially unimpaired for two years.

Comparison of crystal size in different supersaturation modes

Crystallization of a solution of ammonium aluminium sulfate dodecahydrate by cooling and by vacuum evaporation was performed in a laboratory batch experiment. In the two crystallization modes, the nucleation was found to proceed at different rates whereas the crystal growth rate did not differ significantly.

Correlated reorientations in NH4Al(SO4) · 12 H2O single crystals

Single crystals of aluminium ammonium alum NH 4 Al(SO 4 ) 2 •12H 2 O were investigated using dielectric spectroscopy in the frequency range 1 kHz to 1 GHz. On approaching the ferroelectric transition at 58 K from above, a monodispersive polar mode is observed to slow down. The relaxation data can be described in terms of a pure Arrhenius law. The analysis of the dielectric loss reveals that in the paraelectric phase the static susceptibility cannot be described by a single Curie-Weiss law. The thermal variations of the Curie constant indicate that the dipolar correlations of the ammonium ions increase as the temperature is lowered

Correlated reorientations in NH4Al(SO4)2.12H2O single

Single crystals of aluminium ammonium alum NH4Al(SO4)2.12H2O were investigated using dielectric spectroscopy in the frequency range 1 kHz to 1 GHz. On approaching the ferroelectric transition at 58 K from above, a monodispersive polar mode is observed to slow down. The relaxation data can be described in terms of a pure Arrhenius law. The analysis of the dielectric loss reveals that in the paraelectric phase the static susceptibility cannot be described by a single Curie-Weiss law. The thermal variations of the Curie constant indicate that the dipolar correlations of the ammonium ions increase as the temperature is lowered.

Optimum Synthetic Conditions of Ammonium Aluminum Carbonate Hydroxide (AACH) as Starting Material for α-Alumina Fine Powders

Ammonium aluminum carbonate hydroxide (ARCH) as starting material to obtain α-alumina fine powders was synthesized between aqueous solutions of ammonium hydrogen carbonate (AHC) and ammonium alum (AA). The effects of pH of the AHC aqueous solution and reaction temperature on the formation of AACH were discussed. Three products, amorphous aluminum hydroxide, pseudoboehmite (=low crystalline boehmite) and AACH were formed depending on pH. AACH was mainly formed in alkaline aqueous solutions. The optimum synthetic condition of AACH was discussed in terms of the relation between pH and concentration of species calculated by the master variable technique of ionic equilibrium in AHC and AA aqueous solutions. NH4+, AlO(OH)2- and HCO3- species were neccessary to form AACH. Crystallite size of AACH decreased with increasing concentrations of ionic species, [NH4+]⋅[AlO(OH)2-]⋅[HCO3-] and decreasing reaction temperature. Homogeneous, spherical α-alumina particles with a particle size of 0.2μm were obtained by firing at 1050°C for 6h from the AACH with a crystallite size of 50Å synthesized at a pH of 10.0 at 5°C.

Absorption spectrum of Cu 2+ ions doped in ammonium aluminium sulphate single crystal

The absorption spectra of copper-doped ammonium aluminium sulphate single crystals were determined both at room and liquid-nitrogen temperature. The spectrum recorded at room temperature consists of four bands. When the crystal is cooled to liquid-nitrogen temperature, changes in the intensities of the bands are observed. From the magnitude and relative position of the bands, a successful interpretation of all the observed bands has been made and identified as those belonging to Cu 2+ ion in octahedral symmetry. The crystal field and tetragonal field parameters are derived. The observed and calculated energies are in good agreement.

An adiabatic demagnetization refrigerator for SIRTF

An adiabatic demagnetization refrigerator (ADR) has been proposed to cool bolometric infrared detectors on the multiband imaging photometer of the Space Infrared Telescope Facility (SIRTF). One such refrigerator has been built which uses a ferric ammonium alum salt pill suspended by nylon threads in a 3-T solenoid. The resonant modes of this suspension are above 100 Hz. The heat leak to the salt pill is 12 h. The cold stage temperature is regulated with a feedback loop that controls the magnetic field. A second, similar refrigerator is being built at a SIRTF prototype to fly on a balloon-borne telescope. It will use a ferromagnetic shield. The possibility of using a high-T/sub c/ solenoid-actuated heat switch is also discussed. >

水酸化アルミニウムとアルミナについて

The review on the hydroxides and oxides of aluminium is given from the viewpoint of their kinds and structures. Crystalline aluminium hydroxide is composed of five kinds of alumina hydrates due to hydrargillite (and/or gibbsite), bayerite and nordstrandite classified as alumina trihydrate and due to boehmite and diaspore classified as alumina monohydrate. Gelatinous aluminium hydroxide consists of amorphous aluminium hydroxide, pseudoboehmite and intermediate boehmite, indicating the particular increase in the intensity of X-ray diffraction peak at the plane (200) as the orthorhombic structure similar to boehmite. The aluminium hydroxides prepared by various procedures are thermally decomposed to anhydrous aluminas. As it has been reported by many researchers that the thermal transformations of aluminium hydroxides yield anumber of aluminas, such as χ, γ, η, δ, δ1, κ, κ', θ, E, e, ρ and λ, being a transition stage in a process leading ultimately to α-alumina, the thermal decomposition processes are discussed on the basis of the results obtained by the present author. Further the formation of anhydrous aluminas by the thermal decompositions of aluminium salts of inorganic and organic acids such as hydrates of chloride, nitrate and sulphate of aluminium, ammonium alum, formate and acetate of basic aluminium and lactate, citrate and tartrate of aluminium is compared with the thermal transformation processes of aluminium hydroxides to α-alumina. In addition, the preparations of nordstrandite and ρ-alumina are investigated in comparison with the previous results of the author.

The effect of the cooling mode on the kinetic parameters of crystallization

The effect of different cooling regimes (natural, linear, and programmed cooling according to a theoretical curve) on the kinetic parameters of crystallization and on the mean product crystal size is demonstrated by an example of batch cooling crystallization of ammonium aluminium sulphate dodecahydrate. The kinetic exponent g/n determined on the basis of model experiments does not depend on the cooling regime, the system constant BN is highest for the programmed cooling. If this constant is to be a basis for the design of a cooling crystallization equipment, it is necessary to carry out its experimental determination under the same temperature regime.

Thermal decomposition of aluminium-bearing compounds

The thermal decomposition of aluminium sulfate, potassium aluminium sulfate, ammonium aluminium sulfate and alunite have been studied by dynamic thermogravimetry and X-ray diffraction. Specifically, the factors that affect the sulfate decomposition reaction have been investigated. The sulfate decomposition is found to be significantly influenced by the presence of an inert material such as potassium sulfate in the solid matrix.

NMR and dielectric studies of NH4+ motion in some ammonium alums.

Motion of NH4+ and H2O in NH4Ga(SO4)2 · 12H2O and NH4In(SO4)2 · 12H2O has been studied with NMR and dielectric methods. Above the phase transitions at 101 to 111 K and 126 to 128 K, respectively, the NH4+ ions hop and reorient by 90° between two sites, as in NH4Al(SO4)2 · 12H2O. This motion is frozen below Tc.

Growth rate dispersion of small ammonium alum crystals

The growth rates of small (below 60 μm) and large (about 1 mm) crystals of ammonium alum was measured during batch crystallization from aqueous solutions. The growth rate distribution of small crystals is close to normal. With increasing supersaturation the growth rate of the large crystals increases more rapidly than that of small crystals.