Phosphoric acid, Meta Preparation

A satisfactory bath suitable for temperatures up to about 250° may be prepared by mixing four parts by weight of 85 per cent, ortho-phosphoric acid and one part by weight of meta-phosphoric acid the mixed components should first be heated slowly to 260° and held at this temperature imtil evolution of steam and vapours has ceased. This bath is liquid at room temperatures. For temperatures up to 340°, a mixture of two parts of 85 per cent, ortho-phosphoric acid and one part of meta-phosphoric acid may be used this is solid (or very viscous) at about 20°. 

Alkali Meta.IPhospha.tes, A significant proportion of the phosphoric acid consumed in the manufacture of industrial, food, and pharmaceutical phosphates in the United States is used for the production of sodium salts. Alkali metal orthophosphates generally exhibit congment solubility and are therefore usually manufactured by either crystallisation from solution or drying of the entire reaction mass. Alkaline-earth and other phosphate salts of polyvalent cations typically exhibit incongment solubility and are prepared either by precipitation from solution having a metal oxide/P20 ratio considerably lower than that of the product, or by drying a solution or slurry with the proper metal oxide/P20 ratio. 

The chemistry of the amido- and imido-diphosphoric acids is not in a satisfactory state. The interpretation of the experimental work by different investigators is discordant, showing a lack of precise facts. The reports of the preparation and properties of the three amidophosphoric acids indicated above are largely based upon the work of J. H. Gladstone and J. D. Holmes.1 A. Mente s and H. N. Stokes re-survey of the field outlined by J. H. Gladstone and J. D. Holmes shows that the interpretation of the results was probably erroneous in other words, the amido-diphosphoric acids reported by J. H. Gladstone and J. D. Holmes may really be imido-diphosphoric acids, or mixtures of the same with meta- and pyro-phosphoric acids. A number of amidopyrophosphoric acids have been... 

E. D. Chattaway and H. P. Stevens found that phosphoric acid decomposes nitrogen iodide, producing ammonia. According to A. Geuther, when phosphoric acid is treated with phosphorus pentachloride at ordinary temp., phosphoryl chloride and hydrogen chloride are formed phosphorus trichloride furnishes meta-phosphoric and phosphorous acids and phosphoryl chloride is without action in the cold, but when hot, metaphosphoric acid is formed if the phosphoryl chloride be in excess, and phosphorous acid if only a little be present. G. Meyer, and A. Vogel prepared a complex with boric oxide or boric acid—vide boron phosphate, 5. 32, 27. 

Meta- and Pyro-phosphorous Acids.—The acids HP02 and H4P 205 may be regarded as partly dehydrated forms of orthophosphorous acid. In their modes of preparation and proper-ties they recall somewhat the meta- and pyro-phosphorie acids. 

Uses.—Many pharmaceutical preparations contain phosphoric acid or phosphates, or glyeerophosphoric acid, which, as already stated, is made by heating glycerine with the ortho- or meta-acid. Lecithin is an ester of glyeerophosphoric acid which contains choline, (CH3)3 = N(OH) - CH2 - CH2OH, and two molecules of a fatty acid radical (stearyl or oleyl). 

Acid anhydride or acidic monomers, such as 4-methacryloxyethyl trimel-litate anhydride (4-META), 4-methacryloxyethyl trimellate (4-MET), 4-(3-methacryloyloxypropoxy carbonyl) phthalic anhydride (MPRPA), and 4-(4-methacryloyloxybutoxycarbonyl) phthalic anhydride (MBPA), prepared by condensing hydroxyalkyl methacrylates and trimelUtic anhydride acid chloride, are very important coupling agents. The phosphoric acid derivative, MDP is synthesized from methacrylic acid, 1,10-decanediol, and phosphorus oxychloride. These very useful, functional (polymerizable) monomers are added to the primer or liquid part of the adhesive. 

Fig. 10.14 Relationship of solids content and acid doping levels of heat-treated phosphoric acid imbibed meta-PBI prepared by squares sol-gel process, triangles conventional imbibing. Reproduced from [13] with permission of John Wiley and Sons...

Hashimoto and Mitsutani found that phosphoric acid supported on silica, which were calcined at higher temperature (973—1473 K) had a high activity and selectivity for the preparation of isoprene by the decomposition of 4,4-dimethyl-meta-dioxane (MDO). 

When phosphorus pentoxide, or as it is commonly called phosphoric anhydride, is put into cold water, the meta acid is formed. Upon boiling this slowly it reacts with more water and produces the ortho acid. The pyro acid which might be expected as an intermediate product is not formed. This acid, or more usually one of its salts, can be prepared, however, by... 

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