Potassium pyrosulphate, fusion with

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. 

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

Naturally, the flux employed will depend upon the nature of the insoluble substance. Thus acidic materials are attacked by basic fluxes (carbonates, hydroxides, metaborates), whilst basic materials are attacked by acidic fluxes (pyroborates, pyrosulphates, and acid fluorides). In some instances an oxidising medium is useful, in which case sodium peroxide or sodium carbonate mixed with sodium peroxide or potassium nitrate may be used. The vessel in which fusion is effected must be carefully chosen platinum crucibles are employed for... 

The EPA developed two methods for the radiochemical analysis of uranium in soils, vegetation, ores, and biota, using the equipment described above. The first is a fusion method in which the sample is ashed, the silica volatilized, the sample fused with potassium fluoride and pyrosulphate, a tracer is added, and the uranium extracted with triisooctylamine, purified on an anion exchange column, coprecipitated with lanthanum, filtered, and prepared in a planchet. Individual uranium isotopes are separately quantified by high resolution alpha spectroscopy and the sample concentration calculated using the yield. The second is a nonfusion method in which the sample is ashed, the siUca volatilized, a tracer added, and the uranium extracted with triisooctylamine, stripped with nitric acid, co-precipitated with lanthanum, transferred to a planchet, and analyzed in the same way by high resolution a-spectroscopy (EPA 1984). 

For the fusion it is best to start with placing 5 g analytical grade potassium hydrogen sulphate KHSO4 into a clean porcelain crucible. Heat gently over a Bunsen flame, when the hydrogen sulphate slowly decomposes to the pyrosulphate and water. Once foaming has abated, increase the temperature... 

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