Calcium carbonate phosphatic particles

Studies with rats, human adults and some children indicate that calcium-based polishing agents in five commercial and four experimental toothpastes prevent gut absorption of a considerable fraction of fluoride and monofluoro-phosphate owing to complexation [192]. Except for small initial losses of uncomplexed fluoride by interaction with calcium carbonate polishing particles, no major depletion of active ionic fluoride is found to occur in toothpastes over one year [359] but another study indicated considerable losses of free fluoride after only four months of shelf life [341]. It should be noted that analysis with the fluoride electrode might be unreliable in samples containing monofluoro-phosphate [360], glycerin [313] and silica gel [313]. 

Phospha.te Treatment. Calcium phosphate is virtually insoluble in boiler water. Even small levels of phosphate can be maintained to ensure the precipitation of calcium phosphate in the bulk boiler water, away from heating surfaces. Therefore, the introduction of phosphate treatment eliminates the formation of calcium carbonate scale on tube surfaces. When calcium phosphate is formed in boiler water of sufficient alkalinity, a particle with a relatively nonadherent surface charge is produced. This does not prevent the development of deposit accumulations over time, but the deposits can be controlled reasonably well by blowdown. 

An abrasive is usually chemically inert, neither interacting with other dentifrice ingredients nor dissolving in the paste or the mouth. Substances used as dentifrice abrasives include amorphous hydrated silica, dicalcium phosphate dihydrate [7789-77-7] anhydrous dicalcium phosphate [7757-93-9] insoluble sodium metaphosphate [10361-03-2], calcium pyrophosphate [35405-51-7], a-alumina trihydrate, and calcium carbonate [471-34-1]. These materials are usually synthesized to specifications for purity, particle size, and other characteristics naturally occurring minerals are used infrequently. Sodium bicarbonate [144-55-8] and sodium chloride [7647-14-5] have also been employed as dentifrice abrasives. 

Phosphate is also ubiquitous as a minor component within the crystal lattices of other minerals or adsorbed onto the surface of particles such as clays, calcium carbonate, or ferric oxyhydroxides (Ruttenberg, 1992). Therefore, in general, transport of these other particulate phases represents an important transport pathway of P as well. 

As for properties of calcium phophate particles grown in the reactor, chemical and physical analysis were done to verify availability of this process. Table 2 shows results of chemical analysis, which made clear that our products contained mainly calcium phosphate and some calcium carbonate and could be used as the source of fertilizer. 

At times, failures in processing may introduce such materials as carbon adsorbent particles, filter aid, or inorganic compounds. In the last category, iron oxides and sulfides and sodium and ammonium salts have frequently been reported to be factors in the color problem,60 not only because of their own color but also because of their catalytic effect on the formation of coloring materials from sugars. Turbidity may also result from presence of traces of such salts as calcium phosphate, silicate, or sulfate. 

And now that it is, we can reveal that this reaction DOES NOT HAPPEN - calciumn phosphate is insoluble (which is just as well, since large amounts of it are in your bones and teeth). As soon as any particles of calcium carbonate react with phosphoric acid, the reaction stops because the particles are coated with insoluble calcium phosphate. So now we can write Rule 8 (see start of Section 4.2.4 on page 142) ... 

Precipitates Drugs prepared by separating particles from a previously clear liquid by physical or chemical means. Precipitation usually occurs when a hot saturated solution of an amorphous substance is allowed to cool or when a liquid in which the dissolved substance is insoluble is added to its solution. Pharmacists formerly used the process of precipitation as a convenient method of obtaining solid substances in fine particles (precipitated calcium carbonate), to purify solids (precipitated calcium phosphate), or to prepare mercury salts. White precipitate (ammoniated mercury) was first described by Beguin in 1632, a soluble double chloride of mercury and ammonium known to the alchemists as sal alembroth and sal sapientiae, respectively. Red precipitate (red mercuric oxide) was known to alchemists as hydragyrum preci-pitatum per se or precipitate per se yellow precipitate is a synonym for yellow mercuric oxide. " Preserves See Conserves. 

Virtually all dentifrice formulations contain abrasive particles, typically composed of amorphous silica, calcium carbonate, alumina or calcium phosphate. The mechanism by which the toothbrush and dentifrice interact to clean the teeth is one of abrasive cleaning. Toothpaste manufacturers thus aim to provide formulations with effective cleaning power, whilst minimising any wear to the underlying substrate. However, in such a system it is inevitable that some degree of abrasivity will be present, as toothpastes without abrasive particles are unable to prevent the build-up of extrinsic stain [12], It is, therefore, important to understand any abrasion a dentifrice product may cause to the hard tissues in the mouth. 

Only phosphate mineral formation will be considered here. Sulfide equilibria are discussed in detail in Part II and calcium-carbonate saturation states will be considered in another paper (or see Aller, 1977). NH4" is unlikely to be involved in the formation of specific insoluble phases such as struvite (MgNH4P04 6H2O), given the measured concentrations of the ions involved (Martens et al., 1978). The major interactions of with sedimentary particles include reversible and irreversible adsorption reactions (Nommik, 1%5 Mortland and Wolcott, 1%5 Muller, 1977 Rosenfeld, 1979). 

The mineral adsorbs Cl and NO3 ions poorly and reversibly, whilst S04 is precipitated at the mineral surface. Phosphates are preferentially adsorbed on calcium carbonate. Soils which contain CaCOj show pH values ranging from about 7 to 8.4, due to the formation of calcium hydrogen carbonate. The formation of this compound is accelerated in biologically active soils, with a high production of carbon dioxide. Calcareous soils have a soil solution dominated by Ca + ions, and this limits swelling of soil days and prevents the dispersion of finer particles in the soil. If Ca predominates on the exchange complex of soils, the pH value is maintained above 5.5. 

The formation of calcium carbonate particles can be carried out in W/O calcium sulfosuccinate microemulsions [149]. Hollow porous shells of calcium carbonate or reticulated calcium phosphate skeletons made under similar conditions are likely candidates for high technology applications such as the production of lightweight ceramics, catalysts, biomedical implants, and extremely strong membranes [150,151]. Other nanosized inorganic particles can be prepared in W/O microemulsions as well [152-154]. 

Keeping teeth clean requires toothpaste, a mixture of detergents and abrasives, which are hard substances that help remove unwanted materials on the tooth surface. The structure of tooth enamel is essentially that of a stone composed of calcium carbonate (CaCOj) and calcium hydroxy phosphate [apatite—GajQ(PO )g(OH)2], Despite being the hardest substance in the human body, tooth enamel is readily attacked by acids. Because the decay of some food particles produces acids, it is important to keep teeth clean. 

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