Mixture Of Calcium Carbonate Research Articles

Disinfection Effect on Shredded Cabbage by Calcium Oxide Pellets Containing Ferric Oxide.

In order to improve the hydration resistance and handling of calcium oxide (CaO) as an antibacterial agent, CaO pellets containing ferric oxide (Fe2O3) (COPFe) were prepared by heating the mixture of calcium carbonate and Fe2O3. The pellets could keep their shapein water for a long time, and thus the hydration resistance was markedly increased. The COPFe treatment decreasedthe viable counts of bacteria in shredded cabbage, and coliforms were not detected after 5 min with as little as a 0.1% COPFe treatment. During the storage of the cabbage at 4°C for48h, an increase in aerobe counts on shredded cabbage was observed for water treatments but not for COPFe treatment and other treatments (NaOH and sodium hypochlorite).

Use of calcium carbonate - fumed silica mixtures as filler in polyurethane adhesives

Natural ultramicronized calcium carbonate and mixtures of fumed silica-natural ultramicronized calcium carbonate are proposed as fillers of solvent based polyurethane (PU) adhesives. PU adhesive containing only calcium carbonate shows similar rheological, thermal, mechanical, surface and adhesion properties than the PU adhesive without filler. Addition of 90 wt% fumed silica + 10 wt% calcium carbonate mixture to PU adhesive produced a similar performance than the PU adhesive containing only fumed silica. The increase in the amount of natural calcium carbonate in respect to fumed silica in the filler mixture produced detrimental effect on the rheological and mechanical properties of the PU adhesives (in respect to those provided by the PU adhesive only containing fumed silica), although the surface and adhesion properties were not noticeably modified.

Quantitative determination of binary and tertiary calcium carbonate mixtures using powder X-ray diffraction.

The ability to determine the calcium carbonate polymorphic ratio of calcite, aragonite and vaterite in a mixture is important for a variety of applications, particularly the fields of biomineralisation and crystal engineering. Raman spectroscopy and powder X-ray diffraction were used to quantitatively determine the polymorphic composition of both binary and tertiary mixtures of calcium carbonate. It was found that the quantitative detection limits of powder X-ray diffraction were superior to both Raman and infrared spectroscopy.

Properties of polyurethane adhesives containing natural calcium carbonate + fumed silica mixtures

Natural ultramicronized calcium carbonate and mixtures of fumed silica + natural ultramicronized calcium carbonate are proposed as a filler for solvent-based polyurethane (PU) adhesives. The PU adhesive containing only calcium carbonate showed similar thermal, mechanical, surface, and adhesion properties to those of the PU adhesive without a filler. The addition of 90 wt% fumed silica + 10 wt% calcium carbonate mixture to the PU adhesive produced a performance similar to or improved over that of the PU adhesive containing only fumed silica. The increase in the amount of natural calcium carbonate with respect to fumed silica in the filler mixture had a detrimental effect on the rheological and mechanical properties of the PU adhesives, although the surface and final adhesion properties were not noticeably modified. The immediate adhesion (45 min after joint formation) was noticeably increased in the joints produced with the PU adhesives containing fillers, mainly in those with a higher fumed silica content; a cohesive failure in the adhesive was produced in those joints and the mechanical and rheological properties of the PU adhesives determined the immediate adhesion. The failure in the joints peeled 72 h after joint formation was adhesional and the adhesion properties were mainly determined by the surface properties of the PU adhesives. All the adhesive joints showed a similar final adhesion because they have similar surface properties.

Kinetics and mechanism of the carbonation of ettringite

Synthetic, phase pure ettringite has been exposed to a moist CO2 atmosphere at 68 and 88% relative humidity (RH) both at 21–25°C and at 40°C. Physically, the ettringite was carbonated in the form of powders and pellets, pressed to ∼80% theoretical density. Nucleation of decomposition products is a slow process, requiring a definite induction period, the duration of which decreases with both increasing temperature and RH. The surfaces of compacted ettringite pellets, like loose powders, decompose to mixtures of calcium carbonate, calcium sulphate hydrate (both gypsum and hemihydrate), alumina gel and water but the interior of pellets retain water with the result that recrystallization occurs and AFm forms. Pellets more reliably predict the behaviour of industrial ettringite-based cements than loose powders, which are not observed to form AFm

Sinterability of Calcium Oxide Prepared by Heating Mixture of Calcium Carbonate and Calcium Hydroxide

Sinterability of Calcium Oxide Prepared by Heating Mixture of Calcium Carbonate and Calcium Hydroxide

The effect of calcium supplement given with a mixture of calcium carbonate and calcium citrate on the mandibular alveolar bone of pubertal rats

To determine whether the mixture of calcium carbonate and calcium citrate, an oral calcium supplement made from sea shell that is called UNICAL, had any beneficial effect on bone debilitation, we examined the mandibular alveolar bone of pubertal Wistar male rats by bone mineral mass, Ca/P ratio microanalysis, and scanning electron microscopy. (1) Bone mineral mass of UNICAL-fed rats in the low-calcium experiment group was not significantly different than the control group, although its value was significantly higher than in pair-fed standard diet rats. However, although the bone mineral mass of UNICAL diet rats in the calcium-deficient experiment group was significantly higher than in pair-fed standard diet rats, it was significantly lower than in the control group. (2) All Ca : P ratio values in experiment groups were significantly lower than that in control group. Ca : P ratio values of UNICAL diet rats were significantly higher than those of pair-fed standard diet rats in experiment groups. Separately, Ca : P ratio was not significantly different between UNICAL diet rats of the calcium-deficient experiment group and standard diet rats of the low-calcium experiment group. (3) On scanning electron microscope observation, UNICAL diet animals were observed to have more sufficient calcareous microdepositions in bone remodeling areas, which was thought to be one of the morphological indications of bone formation, reflecting active calcium utilization in bone metabolism, than pair-fed standard diet animals. These results suggested that the mixture of calcium carbonate and calcium citrate had a positive effect on bone debilitation to a certain extent in growth-period rats.

Poly(arylene ether)s and poly(arylene thioether)s containing the 1,2‐dihydro‐4‐phenyl(2H)‐ phthalazinone moiety

A series of new high molecular weight poly(arylene ether)s containing the 1,2-dihydro-4-phenyl(2H)phthalazinone moiety have been synthesized. The inherent viscosities of these polymers are in the range of 0.33–0.64 dL/g. They are amorphous and readily soluble in chloroform, DMF, and DMAc. The glass transition temperatures of the polymers range from 241 to 320°C and the 5% weight loss temperatures in nitrogen atmosphere range from 473 to 517°C. The hydroxy group in the monomer 1,2-dihydro-4-(4-hydroxyphenyl)(2H)phthalazin-1-one has been selectively transformed into the N,N′-dimethylthiocarbamate group, which was then rearranged to give the S-(N,N′-dimethylcarbamate) group via the Newman–Kwart rearrangement reaction. A series of poly(arylene thioether)s containing the 1,2-dihydro-4-phenyl(2H)phthalazinone moiety have also been synthesized via two types of reactions, a NC coupling reaction and a one-pot reaction between the S-(N,N′-dimethylcarbamate) and activated dihalo compounds, in diphenyl sulfone in the presence of a cesium carbonate and calcium carbonate mixture. These poly(arylene thioether)s also have high glass transition temperatures (ranging from 217–303°C) and high thermal stabilities. Compared with their poly(ether) analogs, the poly(arylene thioether)s have glass transition temperatures several degrees lower, which is attributed to the more flexible CSC bonds. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 455–460, 1998

Poly(arylene ether)s and poly(arylene thioether)s containing the 1,2-dihydro-4-phenyl(2H)- phthalazinone moiety

A series of new high molecular weight poly(arylene ether)s containing the 1,2-dihydro-4-phenyl(2H)phthalazinone moiety have been synthesized. The inherent viscosities of these polymers are in the range of 0.33-0.64 dL/g. They are amorphous and readily soluble in chloroform, DMF, and DMAc. The glass transition temperatures of the polymers range from 241 to 320°C and the 5% weight loss temperatures in nitrogen atmosphere range from 473 to 517°C. The hydroxy group in the monomer 1,2-dihydro-4-(4-hydroxyphenyl)(2H)phthalazin-1-one has been selectively transformed into the N,N'-dimethylthiocarbamate group, which was then rearranged to give the S-(N,N'-dimethylcarbamate) group via the Newman-Kwart rearrangement reaction. A series of poly ( arylene thioether)s containing the 1,2-dihydro-4-phenyl(2H)phthalazinone moiety have also been synthesized via two types of reactions, a N-C coupling reaction and a one-pot reaction between the S-(N,N'-dimethylcarbamate) and activated dihalo compounds, in diphenyl sulfone in the presence of a cesium carbonate and calcium carbonate mixture. These poly( arylene thioether)s also have high glass transition temperatures (ranging from 217-303°C) and high thermal stabilities. Compared with their poly(ether) analogs, the poly(arylene thioether)s have glass transition temperatures several degrees lower, which is attributed to the more flexible C-S-C bonds.

Novel synthesis of poly(arylene thioether)s via one-pot polymerization of bis(N,N′-dimethyl-S-carbamate)s with activated dihalo aromatic compounds

A novel and convenient method to prepare poly(arylene thioether)s by a one-pot polymerization of N,N′-dimethyl-S-carbamate masked bisthiols was developed. The polymerization reactions were carried out in diphenyl sulfone in the presence of a cesium carbonate and calcium carbonate mixture at 200 – 240 °C. N,N′-Dimethyl-S-carbamate masked bisthiols can be conveniently prepared from the corresponding dihydroxy compounds by the Newman-Kwart rearrangement reaction. A series of novel poly(arylene thioether)s were prepared from 9,9′-bis(4-hydroxyphenyl)fluorene and 2,2′-bis(hydroxyphenyl)hexafluoropropane, respectively. High molecular weight polymers were obtained in 3 – 4 hours.

Cyclic thermogravimetrjc methods for the study of the decomposition of carbonates—CaCO3

The equilibrium decomposition pressure of metal carbonates is difficult to determine accurately using static equilibration techniques, particularly at low temperatures where the time required to reach equilibrium may be excessively long. Furthermore, it has been reported that static methods are subject to kinetic difficulties; thus true equilibrium may never be reached. To overcome these problems, a dynamic approach has been developed. In this study, two different cyclic thermogravimetric methods were used to measure the equilibrium CO2 decomposition pressure of a mixture of calcium carbonate and calcium oxide as a function of temperature. Calcium carbonate was chosen to test the validity of these two cyclic techniques because it is a well-characterized compound. The measurements involved repeated cycling of either temperature or CO2 partial pressure while holding the other parameter constant. The response of the sample to this cycling was a periodic mass variation. Equilibrium was established when a symmetric mass signal was observed with no net mass change. Using these techniques, reliable measurements of the equilibrium CO2 partial pressure were obtained in a relatively short period of time as compared to other methods. The experimental results obtained using the two cyclic methods of analysis agree with currently accepted values. A †H°298.15 value of 179.55 ± 0.16 kJ/mol was calculated for the decomposition reaction of calcium carbonate from the thermal cycling data, and a value of 178.98 ± 0.45 kJ/mol was determined from the partial pressure cycling results.

Effect of alkaline earth metal dopants on the thermal decomposition of the CaCO 3SiO 2 system. Part I

Mixtures of calcium carbonate and silica in a 2:1 molar ratio containing varying amounts of MgO, SrCO 3 and BaCO 3 as dopants were separately subjected to thermal analysis. The decomposition behaviour of these systems is reported here on the basis of TG, DTG and DTA investigations. Activation energies ( E a) and enthalpies (Δ H) for the decomposition reactions have been calculated and the variations in these parameters have been discussed. It was observed that the application of a first-order kinetic equation provides an adequate quantitative description of the DTA curves and E a values, calculated from the thermal data.

Results from experiments comparing aqueous and anhydrous ammonia with ‘nitro-chalk’ for grass cut for silage

SUMMARYIn five experiments made at Rothamsted from 1966 to 1970 ‘Nitro-Chalk’ (ammonium nitrate–calcium carbonate mixture, 21% N) was broadcast for grass cut for silage, either in a single dose in spring or divided equally for three cuts. The ‘Nitro-Chalk’ was used to evaluate anhydrous ammonia (82% N) in 1966, anhydrous ammonia and aqueous ammonia (approximately 26% N) in 1967, 1968 and 1969, and anhydrous ammonia, aqueous ammonia and aqueous urea (18% N) in 1970. All these fertilizers were applied to give 125, 250, 375 and 500 kg N/ha, except in 1968 when 250, 375, 500 and 625 kg N/ha were given.Anhydrous ammonia gave smaller yields (of dry matter) than the other N fertilizers except in 1968, a wet year, when it was at least as good as ‘Nitro-Chalk’, but slightly less good than aqueous ammonia. Yields were larger with autumn- than with springinjected aqueous ammonia and larger with either, than with equivalent single doses of ‘Nitro-Chalk’. Yields with aqueous ammonia were also larger than with ‘Nitro-Chalk’ divided equally for three cuts when more than 375 kg N/ha was tested, but smaller with less. Aqueous urea was as good as a single dose of ‘Nitro-Chalk’ but less good than divided ‘Nitro-Chalk’ in 1970, the only year it was tested. ‘Nitro-Chalk’ divided equally for three cuts gave larger yields than when a single dose of up to 375 kg N/ha was given, but with more N than this a single dose was better.Apparent recovery of N was least from anhydrous ammonia and differed little between autumn and spring injection in 1968, the only year when a valid comparison was possible. Apparent recoveries of N from autumn and from spring-injected aqueous ammonia and from ‘Nitro-Chalk’ broadcast in a single dose differed little, nor did the proportion of the N recovered at each cut. Recovery from ‘Nitro-Chalk’ broadcast in three equal amounts was more uniform, but little larger.Judged by yield, no more than 375 kg N/ha was justified; grass given this amount of N either as aqueous ammonia or as ‘Nitro-Chalk’ removed approximately 29 kg of N, 3 kg of P (7 kg P2O6), 26 kg of K (31 kg K2O) and 2 kg of Mg (3 kg MgO) per tonne of dry matter produced.

Alkaline scale formation in boiling sea water brines

A laboratory method for the study of alkaline scale is described. Evaporator conditions are easily simulated in experiments of relatively short duration (5 hours). Reproducible results have been achieved by chemical analysis for total scale which consisted of mixtures of calcium carbonate and magnesium hydroxide. Experiments with natural sea water show the amount and composition of alkaline scale to be a function of temperature, brine concentration, bicarbonate ion concentration, and flow conditions through the evaporator. The transition between calcium carbonate and magnesium hydroxide was shown to be influenced by factors other than temperature. A new mechanism for alkaline scale formation is proposed in this paper. The first step involves a unimolecular breakdown of bicarbonate ion to form hydroxide ion. This concept is in disagreement with the generally accepted mechanism described in the literature.

Differential thermal analysis using high frequency dielectric heating I. Theory and equipment

AbstractA new analytical technique, differential thermal analysis using high frequency dielectric heating (DTA/HF), has been developed which senses the rate and extent of the enthalpy change accompanying curing. These two parameters relate simply and quantitatively to curing reaction kinetics.In DTA/HF cylindrical samples of uncured elastomers, 2‐in. in diam and about 1‐in. high, enclosed in glass rings and covered, are heated in a high frequency (86 mc) electrical field simultaneously with an identically‐shaped precured reference disc of the same elastomer. Both sample and reference are clamped securely between 3 × 5‐in. rectangular output electrodes. The sample is cured isometrically under pressure generated by thermal expansion. Temperatures at the core of the sample and reference are monitored continuously using ungrounded junction thermocouples with stainless steel probes; both sample temperature and temperature differences between sample and reference are recorded.To test the validity of DTA/HF it was first applied to the dicumyl peroxide (DCP) curing of several cis‐1,4‐polyisoprene calcium carbonate mixtures for which reaction mechanisms and reaction kinetic data are available.

X-Ray diffraction analysis by fluorescent X-ray apparatus

An X-ray diffraction analysis was done by using a fluorescent X-ray apparatus without any modification. Pure metal was placed on the sample holder of fluorescent X-ray spectrometer, and the analysing crystal was substituted by the analytical specimen. The pure metal was bombarded by the X-rays from the X-ray tube, and the fluorescent X-rays produced were diffracted by the sample. The diffracted X-rays were detected by a scintillation counter. Copper plate as pure metal and calcium carbonate, calcium oxide and quartz as specimen were used in this experiment, and the detection limit was examined on the mixture of calcium carbonate and calcium fluoride. The limit of detection was about 10% for calcium carbonate.

The behavior of strontium-90 and cesium-137 in seepage pits at ORNL.

At the Oak Ridge National Laboratory, approximately 40,000 Ci of 90Sr and 150,000 Ci of 137Cs are contained in the vicinity of two intermediate-level, liquid-waste seepage pits that are no longer receiving input of liquid wastes. Radiochemical analyses of cores taken within the area indicate that most of the activity is associated with the soft sludges and precipitates and the first few inches of weathered shale that comprise the side walls and bottoms of the pits. Concentrations of 137Cs and 90Sr were found to be as high as 96 μCi/g (dry weight) and 70 μCi/g, respectively, in the sludge and 415 μCi/g and 32 μCi/g in the first few inches of weathered shale on the side walls and bottom of the pits. The sludge is primarily a mixture of calcium carbonate and illitic clay, with calcium carbonate comprising about 20–50% of the weight. Most of the 90Sr in the sludge is associated with the calcium carbonate, probably as a coprecipitate, while the 137Cs occupies selective exchange sites of the illitic clay. With tritiated water as a tracer, it has been observed that the normal rate of groundwater movement in the waste-pit area is about 0.5 ft/day with a dispersion coefficient of approximately 6 × 10-3 cm2/sec. Predictions of radionuclide movement and dispersion with time have been made, based on the exchange properties of the Conasauga shale for calcium and the critical radionuclides. The predicted migration agrees closely with experience to date and suggests that movement of radiostrontium and radiocesium is not likely to present serious contamination problems in nearby surface streams in the future.

Urinary Calculi

Abstract During the course of this investigation we have encountered two "fakes," both of which were represented by the patients to their respective physicians as having been "passed." They showed less than 2 per cent loss on ignition and proved to be calcium-iron-aluminum silicate rocks. We have also had about a dozen prostatic calculi which were analysed by the "ashing" method. This type of calculus consists of either a mixture of magnesium ammonium phosphate and calcium phosphate, or a mixture of calcium carbonate and calcium phosphate. The above-mentioned stones are, of course, not included in this picture. We hope that this survey and the simple method of analysis presented in these two articles will stimulate further work along this line in various parts of the country. The best similar survey we have seen is that of Leonard and Butt (1) on the types of calculi found in the Pensacola, Florida, area.

Dielectric Constant, Power Factor, and Conductivity of the System Rubber-Calcium Carbonate

Abstract The results obtained in this investigation indicate that either the formula developed by Wiener (Formula 7) or the exponent formula (Formula 9) may be used for the computation of the dielectric constants of mixtures of calcium carbonate and rubber. Formula 7 may be preferred, since it gives some indication of the shape of the particles and state of dispersion of the powder. There was little difference between values of the dielectric constant and loss tangent at 1 kilocycle per second and at 100 kilocycles per second. The change of the loss tangent with the content of calcium carbonate was not large, but a direct relationship between loss tangent and percentage of calcium carbonate was indicated. The 1-minute-conductivity values increased continuously with increasing content of calcium carbonate when Vistanex was used as the base, but passed through a minimum when natural rubber was used.

Dielectric constant, power factor, and conductivity of the system rubber-calcium carbonate

Abstract The results obtained in this investigation indicate that either the formula developed by Wiener (Formula 7) or the exponent formula (Formula 9) may be used for the computation of the dielectric constants of mixtures of calcium carbonate and rubber. Formula 7 may be preferred, since it gives some indication of the shape of the particles and state of dispersion of the powder. There was little difference between values of the dielectric constant and loss tangent at 1 kilocycle per second and at 100 kilocycles per second. The change of the loss tangent with the content of calcium carbonate was not large, but a direct relationship between loss tangent and percentage of calcium carbonate was indicated. The 1-minute-conductivity values increased continuously with increasing content of calcium carbonate when Vistanex was used as the base, but passed through a minimum when natural rubber was used.