Buffering agents calcium carbonate

Wa.terBa.la.nce Chemicals. Water balance chemicals include muriatic acid, sodium bisulfate, and soda ash for pH control, sodium bicarbonate for alkalinity adjustment, and calcium chloride for hardness adjustment. A recent development is use of buffering agents for pH control. One of these products, sodium tetraborate, hydrolyzes to boric acid and a small amount of orthoborate (50) which provides significantly less buffering than carbonate and cyanurate alkalinity in the recommended pool pH range of 7.2—7.8 even at 100 ppm. 

Polyvinyl acetate emulsions for manual application in the production of adhesive bound books were examined for stability. It was found, among other things, that plasticized homopolymers had poor or moderate stability, while copolymer types showed very high stability. The addition of calcium carbonate and calcium acetate could improve the lasting qualities of unstable materials but had little effect on the very stable ones. The addition of these buffering agents made the adhesive less acid and less damaging to papers (6). 

For weakly acidic systems (pH 5-6) in which the accumulation of hydrobromic acid is prevented by buffering agents such as calcium carbonate or benzoic acid salts, more information is available. Isbell and Pigman have made an extensive study of such systems, including a thorough consideration of the effect of the concentration of total bromine, free bromine, hypobromous acid and bromide ion on the velocity of the reaction. The results very definitely showed a direct correlation between free bromine concentration and the velocity of the oxidation. No such correlation could be found with hypobromous acid. The results are shown in Tables VII and VIII. The velocity constants were determined for a- and for 8-D-glucose. In the table for /S-D-glucose, in experiments 2 and 5, the hypobromous acid concentration varied 1 10 but the reaction rate varied 1 3. The variations in free bromine concentration follow the variations in the reaction rate constants and the kf values are based on the assumption that free bromine is the oxidant. The concentration of the oxidant (a in equation 31) is therefore the concentration of free bromine. 

The use of buffering agents in solid dose forms is not as widespread as the use in parenteral products. Nevertheless, the current Handbook of Pharmaceutical Excipients lists calcium carbonate, monobasic and dibasic sodium phosphate, sodium and potassium citrates, and tribasic calcium phosphate as potential buffering agents. ... 

Calcium ions are undesirable in alkaline flood solution, and their concentration must be kept to a very low value. This is ordinarily accomplished by using a sodium carbonate buffer, which removes calcium as it exchanges off the clay by precipitating it as insoluble calcium carbonate. In doing so, however, carbonate ions, which are the buffering agent in the system when sodium carbonate is used, are also removed. Thus, reaction with calcium on the clays also consumes the alkaline solution as it moves through the reservoir. 

Buffering agents are used To counter the acidic effects of peat and other casing materials. Calcium carbonate (CaCOa) is most commonly used and comes in different forms, some more desirable Than others. 

Oyster Shell Comprised of calcium carbonate, ground up oyster shell is similar to limestone grit in its buffering action and its structural contribution to the casing layer. But oyster shell should not be used as the sole buffering agent because of its low solubility in water... 

Didanosine is extremely acid labile at pH values below 3, so one ofthe formulations contains buffering agents (dihydroxyaluminium sodium carbonate and magnesium hydroxide) to keep the pH as high as possible to minimise the acid-induced hydrolysis. Ciprofloxacin forms insoluble non-absorbable chelates with these metallic ions in the buffer so that its bioavailability is markedly reduced. See also Quinolones + Antacids or Calcium compounds , p.328. 

Clearly some form of sample pretreatment is required for soils and sediments. Total levels may be obtained following sodium carbonate-boric acid fusion and the dissolution in hydrochloric acid employing lanthanum as a buffer and releasing agent. If the determination of silicon is not required, it may be volatilized as silicon tetrafluoride using hydrofluoric acid, although some calcium may also be lost as calcium fluoride. For many samples, however, it may be more appropriate to determine the exchangeable cation content of the sample. Here, the sample may be shaken with an extractant solution, for example, 1 mol 1 ammonium chloride, ammonium acetate, or disodium EDTA, prior to filtration and analysis. Where final solutions contain more than - 0.5% of dissolved material, the standards should also contain the major constituents, even where no chemical interference is expected, in order to match the viscosity and surface tension and avoid matrix effects. 

When they further observed that the normal nucleus contains a high proportion of mono-, di-, and trinucleotides of adenine, they claimed to have provided direct proof of their theory by demonstrating that the mono-or dinucleotides in the nucleus may be converted to ATP when oxygen is present. (The nucleotides can be extracted from the nucleus with acetate buffer at pH 5.1.) This conversion certainly suggested the existence of an intranuclear process of oxidative phosphorylation. As in mitochondria, oxidative phosphorylation in the nucleus is inhibited by uncouplers or agents blocking the electron transport chain. Nuclear oxidative phosphorylation is blocked by cyanide, azide, and antimycin A, or by dinitrophenol but, in contrast to mitochondria, it is resistant to Janus green, methylene blue, carbon monoxide, Dicumarol, and calcium. 

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