Grahams Salt

Soluble glassy polyphosphates have many of the applications of the crystalline varieties already dealt with, for example, deflocculation, water softening and detergency (Section 12.6). 

3 Phosphate/Silicate, Phosphate/Arsenate and Phosphate/Sulphate Classes 

a high arsenic content glass will undergo extensive hydrolysis immediately on dissolution, and produce a much greater proportion of short chains than would be obtained from a pure polyphosphate glass (12.61a). 

Fusion of a phosphate with a silicate does not easily give a condensed polymer of Si04 and PO4 (12.62). Calcium metaphosphate fused with silica gel at 980°C (Si02 12.5%) gives a clear glass which is slowly but completely soluble in water. If the silica content is 12.5%, the resulting glass is turbid and not completely soluble in water. 

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For example, sodium hexametaphosphate, which is also called Graham salts and which is a common food additive, generally has a chain length of 10 to 15 phosphorus atoms, not 6 phosphorus atoms as the name implies (26). 

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. 

Graham similarly adopted the new notation "in such cases where it may be expedient," for example, in expressing his results for the acids and salts of phosphorus.67 The British Association for the Advancement of Science constituted a committee that reported in 1835 that a majority of the sixteen members approved the new "continental" notation, with the proviso that "it is desirable not to deviate. . . from algebraic usage except so far as convenience requires."68... 

Recently Hoover 29> compared various extrapolation methods for obtaining true solution resistances concentrated aqueous salt solutions were used for the comparisons. Two Jones-type cells were employed, one with untreated electrodes and the other with palladium-blacked electrodes. The data were fitted to three theoretical and four empirical extrapolation functions by means of computer programs. It was found that the empirical equations yielded extrapolated resistances for cells with untreated electrodes which were 0.02 to 0.15 % lower than those for palladium-blacked electrodes. Equations based on Grahame s model of a conductance cell 30-7> produced values which agreed to within 0.01 %. It was proposed that a simplified equation based on this model be used for extrapolations. Similar studies of this kind are needed for dilute nonaqueous solutions. 

Iodine is essential in the mammalian diet to produce the thyroid hormone thyroxine deficiency in humans causes goitre. Collectively, deficiencies of iodine, iron, zinc and vitamin A in humans are thought to be at least as widespread and debilitating as calorie deficiencies (Welch and Graham, 1999). The main source of iodine in soils is oceanic salts rather than parent rock, and so deficiency is most widespread in areas remote from the sea (Fuge, 1996). In principle deficiency is easily corrected with dairy supplements. However in practice this is not always feasible. Addition of iodate to irrigation water has successfully corrected widespread iodine deficiency in parts of China where the usual methods of supplementation had failed (Cao et al., 1994 Jiang et al 1997). However there is not much information on the behaviour of iodine in soil and water systems. 

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... 

Thomas Graham (103,104) recognized very clearly that water may have different functions in salts, and particularly in the phosphates. He discovered that the different phosphates differed from one another not only... 

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. 

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