Metaphosphate mineral

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. 

Sodium Metaphosphate, Insoluble, occurs as a white, crystalline powder. It is a high-molecular-weight sodium polyphosphate composed of two long metaphosphate chains (NaP03) that spiral in opposite directions about a common axis. The Na20/P205 ratio is about 1.0. It is practically insoluble in water but dissolves in mineral acids and in solutions of potassium and ammonium (but not sodium) chlorides. The pH of a 1 3 slurry in water is about 6.5. 

As discussed in Chapter 3, though phosphates exist in three structural forms, orthophosphates, pyrophosphates and metaphosphates, they are found in nature mainly as orthophosphates. The acid phosphates used in the synthesis of CBPCs, as well as the resulting products that constitute CBPCs are also orthophosphates, and therefore, this chapter is focused on orthophosphate minerals. Readers interested in other types of phosphates are referred to the excellent review by Corbridge et al. [1]. 

The factor most influential in determining the outcome of a condensation reaction is the catalyst. The catalysts most commonly employed are mineral acids, although copper(lI) sulfate, phosphorus pentaoxide, ethyl metaphosphate, cation-exchange resins in the acid form, and zinc chloride (alone - or in combination... 

Potassium metaphosphate CAS 7790-53-6 EINECS/ELINCS 232-212-6 Synonyms Metaphosphoric acid potassium salt Monopotassium metaphosphate Potassium Kurrol s salt Potassium polymetaphosphate Classification Mineral salt Definition Straight-chain polyphosphate Empirical KO3P Formula KPO3... 

Crystalline rhombohedral NZP, has an open three-dimensional channel-type structure built from corner-sharing tetrahedral PO4 and octahedral ZrOg units. It contains two possible sites for the Na cations, only one of which is occupied. The mineral kosnarite KZr2(P04)3 also has a similar type structure [40,41]. The sodium salt, which has a very low thermal expansion coefficient, can be prepared by heating together appropriate quantities of sodium metaphosphate and ZrOj at 1200°C [42]. 

Sperm heads are treated with dilute mineral acid (hydrochloric or sulfuric) (Kossel, 1929). By adding a solution of anion such as picrate to the acid extract, protamine is precipitated as an insoluble salt, which is further converted into sulfate or hydrochloride. In the original method of preparation of a protamine from testes of Rhine salmon, Miescher (1897) used 1—2 % hydrochloric acid for the extraction and platinum chloride for the precipitation of protamine. Kossel (1929) used 1 % sulfuric acid while Stedman and Stedman (1951) used 0.1—0.5 N sulfuric acid in their complete extraction procedure . Block et al. (1949) isolated the sulfate salt of clupeine and salmine on a larger scale, using 0.2 N hydrochloric acid and metaphosphate, respectively, as the extracting and precipitating reagents. 

A method for the preparation of HA fibers was established using a solid phase reaction [66]. With this method, the HA fibers were fabricated by heating a compact consisting of calcium metaphosphate fibers with calcium hydroxide panicles at 1000°C in air atmosphere, and subsequently treated with dilute aqueous HCl solution to remove unwanted secondary phase substitution such as CaO. The obtained HA fibers were characterized and found that the nanostructural characteristic features of HA are quite similar to the natural bone mineral apatite phase. Therefore, the solid-state reaction can be considered as one of the capable methods for the production of nanostructure HA. 

The P—O—P link in polyphosphates is readily hydrolysed in excess water, metaphosphates revert to orthophosphate. So, unlike the condensed silicates, polyphosphates are never found as minerals. 

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