Calcium carbonate demonstration

Fig. 5. Two samples of a nominally 15-p.m calcium carbonate powder, tumbled in the free-fall tumbling mixer/sampler, taken nine minutes apart. The similarity between the two samples demonstrates that these are probably representative of the bulk powder.

Of course, this argument is perfectly true where it can be positively demonstrated that MU water requirements really are very low. Once again however, if this is not the case, then—most treatment programs are designed primarily for corrosion control and do not compensate for undue hardness entering the boiler—calcium carbonate scale can and does develop over time. This process takes place even where the MU water is relatively soft, and results in the formation of insulating boiler tube deposits or boiler vessel sludge. 

Changing catalyst support from carbon to calcium carbonate leads to dramatic improvement of the cis/tran ratio from 6 1 to 18 1, that is the cis selectivity increases from 85.7% to 94.7%. The reason for better selectivity on CaC03 supported catalyst is attributed to its lower surface area leading to lower hydrogenation activity, but more selective to the desired product. The successful commercialization of the new route for sertraline synthesis demonstrates that for a stereoselective hydrogenation reaction, improve product selectivity can be achieved by proper selection of catalyst support. 

Meat consumption was accompanied by more sulfate output in the urine. This agrees with earlier feeding studies in which animals were fed any of several fixed acids which had been reported to result in increased calcium loss (13, 17). Feeding hydrochloric acid, Goto (17)showed that calcium carbonate was simultaneously lost from the bones of rabbits. A similar conclusion was drawn by Steenbock, et al. (13) who demonstrated a loss of both calcium and phosphorus mediated by hydrochloric acid. These data were consistent with the sulfate infused dog. In the dog, Walzer and Browder (15) showed that sulfate feeding increased calcium losses along with sulfate loss. This confirmed results that Lamb and Evvard (32) reported for the Pig-... 

RP-HPLC with gradient elution was employed for the study of the influence of theaflavins and thearubigins on the adsorption of black tea on calcium carbonate. Separation of tea constituents was performed in an ODS column (250 X 4.9mm i.d. particle size 5 im). Aqueous solvent was 1 per cent citric acid, pH adjusted to 2.8 with sodium hydroxide and the organic solvent was ACN. The gradient initiated at 8 per cent ACN, was increased to 31 per cent in 50min. Theaflavins and thearubigins were detected at 460 nm, while total polyphenolics were detected at 280 nm. The flow rate was 1.5 ml/min. The results demonstrated the involvement of theaflavins and thearubigins in the adsorption process [185],... 

Dissolving an eggshell in vinegar demonstrates a modern environmental problem. Calcium carbonate is present in Earth s crust as marble, limestone, and chalk. Many modern buildings, statues, and stone structures contain calcium. Acid rain is slowly dissolving these structures. 

One demonstrated solution to this problem is to raise the pH of acidified lakes and rivers by adding calcium carbonate—a process known as liming. The cost of transporting the calcium carbonate coupled with the need to monitor treated water systems closely limits liming to only a small fraction of the vast number of water systems already affected. Furthermore, as acid rain continues to pour into these regions, the need to lime also continues. 

The existence of alkyl- or aryl calcium amides has not as yet been unambiguously demonstrated. One reason for this seems to be because calcium— carbon bonds are much less stable than calcium—nitrogen bonds, as is illustrated by the following reaction [Eq. (2)] (12). 

Fortunately, the absence of such irreversible attachment to E-glass did not extend to other important substrates. Early work conducted with ATH (alumina trihydrate), calcium carbonate, and titanium dioxide demonstrated irreversible attachment to such substrates [2, 3], thereby laying the foundation for use in a diverse array of non-fiberglass applications. 

Gupta, H., Thomas, T.J., Park, A.-H.A., Iyer, M.V., Gupta, P Agnihotri, R Jadhav, R.A., Walker, H.W., Weavers, L.K., Butalia, T., Fan, L.-S. et al. (2007) Pilot-scale demonstration of the OSCAR process for high-temperature multipollutant control of coal combustion flue gas, using carbonated fly ash and mesoporous calcium carbonate. Industrial and Engineering Chemistry Research, 46(14), 5051-60. 

M 54] [P 48] Separation-layer micro mixers with concentric multi-layered outlets can be operated in a droplet-forming mode [53] If fast precipitating solutions are contacted in this way with a solvent layer for initial separation, the part of the droplet close to the tube outlets remains transparent, which demonstrates that a tri-layered system still exists with the two reacting solutions not being intermixed, as evidenced by calcium carbonate formation in aqueous solutions as described in [39,136], At the droplet end cap the layers collide and circulation flow sets in. As a result, mixing is achieved and precipitation occurs. The circulation patterns are visualized by the particle trajectories. 

A solution of 20 g of desoxycorticosterone in 190 ml of absolute ethanol was stirred in an atmosphere of hydrogen in the presence of 1.68 g of 25% palladium on calcium carbonate catalyst. After 20 hours, approximately 1 molar equivalent of hydrogen had been absorbed and hydrogen uptake had ceased. The catalyst was removed by filtration and the filtrate evaporated in vacuo to yield 20 g of nearly pure product, MP 135°C to 140°C. The crude product was demonstrated to be free of starting material by paper chromatography. A highly purified product was obtained by recrystallization from acetone-water with cooling in an ice bath, yield 14.5 g, MP 152°C to 154°C. The product was characterized by analysis and by absence of ultraviolet absorption. 

The importance of the interaction of organic compounds with calcium carbonate surfaces has long been recognized. It has been demonstrated that aragonite precipitation is inhibited by uncharacterized dissolved organic matter (Chave and Suess, 1967), and that humic and fulvic acids, and certain aromatic carboxylic acids, inhibit seeded aragonite precipitation from seawater (Berner et al., 1978). The selective adsorption of amino acids on carbonate substrates has received considerable attention. A preferential adsorption of aspartic acid has been shown from humic and fulvic acids and proteinaceous matter (Carter and Mitterer, 1978 Carter, 1978 Mitterer, 1971). 

An estimate of the calcium carbonate accumulation rate based on pilot unit experience is shown as the dashed line in Figure 7. This concept for calcium carbonate control is to be demonstrated in the 250 T/D pilot plant during operations on a subbituminous coal. 

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