Graham s salt

Galena, see Eead sulfite Glauber s salt, see Sodium sulfate 10-water Goethite, see Iron(II) hydroxide oxide Goslarite, see Zinc sulfate 7-water Graham s salt, see Sodium phosphate(l —) Graphite, see Carbon... 

Grafting of polymers Graft polymerization Graft versus host disease Grahamite Graham s salt Grain... 

In Justus von Liebig s laboratory, Fleitmann and Henneberg found that there were several metaphosphates with different properties, all of which had the formula MePC>4 (Me = monovalent metal ion). The story then becomes complicated, and mistakes in nomenclature led to ambiguities in this class of compounds. As well as Graham s salt there is a Maddrell s and a Kurol s salt . All have the same formula, NanH2Pn03n+i, but differ in structure and chain length. 

Gouy method, 32 4, 10 Graham s salt, 4 4, 5, 6, 7, 10-11, 39 glasslike, 4 41-50 tetrametaphosphates from, 4 20 trimetaphosphate from, 4 44-45 ultraphosphates from, 4 56 Grain coarsening, 31 14 Graphite... 

Even before the above facts and structural considerations were generally appreciated by chemists, some of the polyphosphates, such as Graham s salt and the triphosphate, for example, had acquired major technical importance 90, 91,127,129, 249). About thirty years ago the study of condensed phosphates was taken up from many sides in attempts to determine their structures and, from their structures, to understand their properties. Preparative methods, physico-chemical investigations and theoretical considerations were all brought into play in order to develop this branch of inorganic chemistry to a point where, today, the perspective is clear and we can regard it as well-investigated. 

It seemed probable, from the early results of chromatography, that the hydrolyzate from Graham s salt contains metaphosphates with more than four phosphorus atoms in the anion ring 350). A little later 186) the metaphosphate content of a freshly prepared solution of Graham s salt with a mean chain length n of 100-125 was given as ... 

Percentage of Meta phosphates with Various Numbers of Units in the Anion Ring in Graham s Salt... 

Alkali oligophosphates are soluble in water either individually or when in the form of glass-like mixtures, and their solutions form precipitates with polyvalent cations which are soluble in excess of the phosphate. Their physical properties are described in Section IV,E,/,e since they are related to those of glasses of the type of Graham s salt with anions of large chain length. 

Chemical proof that the anions in Graham s salt arc linear chains of P04 tetrahedra follows from the observation that arsenato-phosphate glasses analogous to Graham s salt (see Section VI) are broken down on aqueous hydrolysis into ortho arsenate and mixture of low molecular polyphosphates with a mean chain length dependent only on the P As ratio in the glass (295, 308). 

In addition, solutions of Graham s salt prove to be identical in their chemical behavior with those of Maddrell s salt (295, 816), the chain-like nature... 

Physical properties of solid polyphosphate glasses and their melts are also in accord with the conclusions drawn from chemical studies. The X-ray diffraction pattern shows the polyphosphate anions to consist of long chains of P04 tetrahedra (32) and the same conclusion is reached by studying the double refraction of fibers formed by rapidly drawing supercooled melts of Graham s salt (101). 

The linear polymer components of Graham s salt are high molecular... 

Fig. 8. Mean chain lengths in the formation of Graham s salt. T = 650°C Pn,o = 55.3 Torr.

Formation of trimetaphosphate anions from those of Graham s salt also occurs in solution. In water this process is not associated with hydrolytic cleavage of the P—0—P bonds, as was at first assumed (10, 322), but is independent of it (361). Thus polyphosphates of long-chain amines which are soluble in benzene form trimetaphosphate quantitatively on warming the anhydrous solution (359). This transformation follows Ostwald s rule for successive transformations, since trimetaphosphates are more stable than polyphosphates (322). 

Partial replacement of cations when using excess of alkali phosphate was at first interpreted by supposing that the cations were in part bound as a complex with the polyphosphates. This led to incorrect conclusions regarding the molecular size of polyphosphates, which persist even now in the designation of Graham s salt as hexametaphosphate. The correct interpretation of these very complicated relationships stems from the discovery that in dilute solutions of polyphosphates even salts of the alkali metal ions are only partially dissociated—up to a maximum of 30-40% 260, 280, 282, 288, 333). The degree of dissociation a for alkali polyphosphates depends on many factors. Thus, for example, the effective degree of... 

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