Condensed polyphosphates, effects

As for pure phosphoric acid, the transport properties of PBI and phosphoric acid also depend on the water activity, this is on the degree of condensation (polyphosphate formation) and hydrolysis. There is even indication that these reactions do not necessarily lead to thermodynamic equilibrium, and hydrated orthophos-phoric acid may coexist with polyphosphates in heterogeneous gel-like microstructures [99]. There is not much known on the mechanism of proton transport in polymer adducts with polyphosphates and/or low hydrates of orthophosphoric acid. Whether the increased conductivity at high water activities is the result of the plasticizing effect of the water on the phosphate dynamics, thereby assisting proton transfer from one phosphate to the other, or whether the water is directly involved in the conduction mechanism has not been elucidated. 

There is an optimum concentration of surface-active substances for which a maximum reduction in adhesive force is achieved. This is confirmed by our experimental results for aqueous solutions of OP-10 (Fig. IV.19). On raising the concentration of surface-active substances to 1% adhesion diminishes (curves 2 and 3). Further raising the concentration (above 1%) causes micelle formation and has little effect on adhesion. A similar effect is exerted on the adhesion of particles in an aqueous medium by the complex-forming substance sodium hexametaphosphate (curves 1 and 4). Our experiments based on sodium hexametaphosphate with a tracer phosphorus atom show that, like certain condensed polyphosphates [197] this substance may collect on the surface of the contiguous bodies and thus facilitate the detachment of particles. 

One of the most effective methods for controlling crystallization fouling is by adding chemical inhibitors to a scaling water. Commonly used antisealants are derived from chemicals such as condensed polyphosphates, organophospates, and polyelectrolytes. 

Condensed (poly) phosphates may exert different effects on calcium utilization than the aforementioned effects of simple (ortho-) phosphates. Polyphosphates have a much greater affinity for calcium than do orthophosphates, and soluble calcium-polyphosphate complexes are readily formed in the gastric and intestinal environments. In addition, polyphosphates must be hydrolyzed by an intestinal alkaline phosphatase (27) prior to absorption. We have found polyphosphates to be incompletely (80.5%) hydrolyzed to orthophosphate during the digestive process in young adult males when calcium intake was low only 56% of a 1 g phosphorus supplement was absorbed from a polyphosphate sources as compared to 71% from an orthophosphate source (5). 

Since all condensed phosphates are ultimately degraded to monophosphate in hot solution, especially at low pH, the total phosphorus(V) content of a substance may readily be determined after hydrolysis either gravimetrically or titrimetrically (109). However, as soon as it is a question of estimating the content of separate components in mixtures of condensed phosphates insuperable difficulties are encountered if methods depending on precipitation, titration, or a combination of the two are used. Even a quantitative precipitation of monophosphate is impossible if polyphosphates with chain length of n = 3 or more arc present in the solution. The precipitating cation and the compound to be precipitated by it are partly kept in solution by the polyphosphate part of the polyphosphate is also carried down by the precipitate. Both of these effects depend in their extent in different ways on the nature and quantity of the substances present and the analysis gives a correct quantitative result only in isolated instances... 

Naratriptan was also prepared using the Fischer indole reaction (Scheme 15). Thus hydrazine 43 was condensed with Al-methyl-4-piperidineacetaldehyde in aqueous HCl to form hydrazone 44. Fischer indohzation was effected by treating 44 with polyphosphate ester in refluxing CHCI3 to provide naratriptan (3) in low yield. Higher yields may be attainable with the use of milder Fischer cyclization conditions (i.e. acetic acid or aqueous HCl). 

Diammonium phosphate and ammonium sulfamate are used at 15 % solids addon and function as condensed phase flame retardants, not only by crosslinking but also by dehydrating cellulose to polymeric char with reduced formation of flammable by-products (Fig. 8.6). The water insoluble ammonium polyphosphate is an effective flame retardant and is added to coatings and binder systems, for example for pigment printing. Ammonium bromide is applied at 10 % solids add-on and is effective in the gas phase. 

Effect of the Forms of Phosphorus. The first factor to be considered in this review is the effect of different forms of phosphorus on trace element utilization. Inorganic phosphorus may occur as simple orthophosphates or condensed phosphates (Figure 1). The condensed or polymeric phosphates include pyrophosphates and polyphosphates. Unfortunately, the nomenclature used to identify most food grade polyphosphates is confusing. 

Polyphosphates are effective cathodic inhibitors for aerated cooling systems [5,6]. They are also known as condense or polymer phosphates. They bond with calcium ions to form positively charged colloidal particles that form a barrier film on the cathode (Fig. 14.7) [6], A disadvantage of this inhibitor is hydrolysis of phosphoms oxygen bond, resulting in orthophosphate, a less desirable inhibitor. 

Ammonium polyphosphate appears to cross-link the polymer at high temperatures, thus increasing the probability of carbon-carbon bond formation in the condensed phase. There are, however, a number of problems with this method. For example, the temperature at which the polymer begins to degrade is decreased and, because substantial amounts of inorganic salts are required to be effective, they modify the mechanical properties of the PU foam. A particularly disconcerting observation was that under certain conditions toxic phosphorus compounds may be formed with disastrous consequences for human life. 

These are often melamine and derivatives or polyphosphate compounds such as APP. The mode of action of melamine appears to involve endothermic sublimation, acting as a heat sink, vapour-phase dissociation and also self-condensation under suitable conditions. APP achieves its flame retardant effect by intumescence and char formation acting as a barrier to combustion reactions. 

In order to avoid laborious and time-consuming procedures for converting the phosphoms to measurable phosphate ions some improved methods have been reported that may be effective for online monitoring, e.g. thermal induced digestion, ultraviolet photooxidation [110], and microwave-assisted digestion [81,97,105]. Whatever the choice, it is important to ensure that quantitative oxidation of relatively refractory organic phosphoms compounds, i.e. condensed phosphates, and further hydrolysis and release of P from polyphosphates occurs prior to the detection step. 

There have been further reports on the rate enhancement observed when the normal complex [Ni(pada)] is formed in the presence of micelles. These can be very considerable but it has been found that sodium alkanesulfonates are about 25% less effective in this respect than the alkyl sulfates. The effect of various anionic polyelectrolytes on this reaction has also been studied it ranges from an acceleration of about two orders of magnitude in the case of poly(styrene sulfonate) to a retardation by about one order of magnitude for polyphosphate and seems to be dependent on the state of hydration of the Ni ion when condensed in the polyelectrolyte domains. Polyphosphate exerts a similar retardation on the formation of [CoCpada)] " and the effect is attributed to the complete replacement of the coordinating water by the polyelectrolyte. Activation... 

This type of reaction was first applied to the preparation of polyamides, as discussed above, for which it is somewhat more effective in forming high molecular weight polymers, but it has now been used for the synthesis of a wide variety of aromatic polyesters, either by the self-condensation of hydroxyacids or by the co-condensation of dicarboxylic acids and difunctional phenols.A fairly wide variety of phosphorous compounds can be used as reducing or dehydrating agents in these reactions, in addition to phosphines, including phosphites, chlorophosphates, phosphates, polyphosphates and phosphazenes. In most cases, lithium chloride is added and the reaction is run in either pyridine or an amide solvent system. The reaction has also been found to be catalyzed by tertiary amine salts. 

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