Potassium pyrosulphate

Substances which are insoluble or only partially soluble in acids are brought into solution by fusion with the appropriate reagent. The most commonly used fusion reagents, or fluxes as they are called, are anhydrous sodium carbonate, either alone or, less frequently, mixed with potassium nitrate or sodium peroxide potassium pyrosulphate, or sodium pyrosulphate sodium peroxide sodium hydroxide or potassium hydroxide. Anhydrous lithium metaborate has found favour as a flux, especially for materials containing silica 12 when the resulting fused mass is dissolved in dilute acids, no separation of silica takes place as it does when a sodium carbonate melt is similarly treated. Other advantages claimed for lithium metaborate are the following. 

The soil samples were first heated to fumes with a mixture of nitric and sulphuric acids. This method gave appreciably higher arsenic recoveries (95-102%) than fusion with potassium pyrosulphate and was considerably more rapid than fusion with a mixture of nitric and perchloric acids. 

Fusion with a flux such as sodium hydroxide, potassium bifluoride potassium pyrosulphate has been used extensively in the water industry. 

The isothermal solubility curve of mixtures of potassium sulphate and sulphuric acid expresses the composition of the soln. at 25° in equilibrium with the solid phase or phases, when the mol. ratio of K2SO4 and SO3 per 1000 grms. of soln. are plotted as co-ordinates. The ranges of stability in the ternary system K20—S03—H20, are diagrammed in Fig. 51, where the conditions have been studied in the vicinity of the SOs-apex, as far as the formation of KHS207, hut not as far as the well-known potassium pyrosulphate. The meaning of the diagram... 

Potassium sulphate, when warmed with chlorosulphonic acid, yields potassium pyrosulphate,9 the reaction being analogous to that of sulphuric acid with the chloro-aeid silver nitrate is vigorously converted into silver chloride, with concurrent formation of nitrosulphonic acid.10... 

When titanium is found, it is best to fuse with potassium, pyrosulphate in a silica or platinum crucible, and to extract the residue with cold water whereby a solution of titanium(IV) sulphate is obtained. 

Reactions of titanium(IV) ions To study these reactions use a 0-2m solution of titanium(IV) sulphate, which is prepared either by dissolving the reagent [Ti(S04)2] in 5 per cent sulphuric acid, or by fusing titanium dioxide TiOz with a 12—15 fold excess of potassium pyrosulphate in a porcelain or platinum crucible. 

Potassium pyrosulphate, K O,.—The pyrosulphate is produced by heating potassium hydrogen sulphate, or by the action of sulphur trioxide on the normal sulphate. It forms colourless crystals, melting9 above 300° C., and of density 2-277. The heat of formation is 474-2 Cal.10... 

Potassium hydrosulphate Hydrated potassium trihydrodiaulphate Potassium trihydrodisulphate. Potassium hycto-pyroamphate Potassium pyrosulphate. ... 

Indoxylsulphuric acid may be obtained by heating indoxyl with potassium pyrosulphate [12]. It exists only in the form of its salts. These are eolourless and yield indigo blue on heating or on oxidation. 

Standard rhodium solution 1 mg/ml. Fuse 0.1000 g of metallic rhodium powder with 2 g of potassium pyrosulphate in a silica crucible. Dissolve the melt in hot 1 M HCl and make the solution up to volume with this acid in a 100-ml standard flask. 

If not clean the crucible is dried and fused with potassium pyrosulphate (K2S2O7), the melt is poured into dry waste sand and the residue dissolved from the crucible in warm 6(N) HCl. 

Fusion with sodium fluoride-potassium pyrosulphate-concentrated sulphuric acid. Digestion with fuming sulphuric acid-ammonium sulphateconcentrated nitric acid. 

Unlike platinum, palladium is slowly dissolved by concentrated nitric acid, and by hot concentrated sulphuric acid, forming a brown solution of palladium(II) ions. Palladium can also be dissolved by fusing the metal first with potassium pyrosulphate and then leaching the frozen melt with water. The metal dissolves readily in aqua regia, when both Pd and Pd (more precisely, [PdC ] and [PdCls] ) ions are formed. If such a solution is evaporated to dryness, the latter loses chlorine so that on treating the residue with water a solution of palladium(II) ions is obtained. Palladium(II) ions are most stable palladium(III) and (IV) compounds can easily be transformed into palladium(II). 

Titanium(IV) sulphate (0.2m). Dilute 33 ml 15% (w/v) commercial titanium(IV) sulphate solution with m sulphuric acid to 100 ml. Alternatively, fuse titanium dioxide Ti02 with a 12-15 fold excess of potassium pyrosulphate in a porcelain or platinum dish, and dissolve the residue in 3m sulphuric acid. If necessary, filter the solution, or use the clear, supernatant liquid for the tests. 

T. J. Cullen, Potassium pyrosulphate fusion technique in determination of copper in mattes and slags by x-ray spectroscopy, AmiH Chem., 32 516-511 (1960). 

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