Eschka mixture

Determination of Chlorine in the Polymers. The chlorine content was determined by heating 0.1-1 gram of the substance to be analyzed to 700°C with a large excess of Eschka mixture. After cooling, the mass was treated with 6N nitric acid, and the chlorine present in die solution as silver chloride was precipitated, filtered, and dissolved again in an aqueous solution of ammonia. From this solution, silver was precipitated as mercaptobenzothiazolate, which allows determination of the chlorine content in the material under examination (15). 

The gasification method consists of mixing coal with a mixture of two parts of the Eschka mixture (i.e., 67% w/w light calcined magnesium oxide and 33% w/w anhydrous sodium carbonate), six parts of soda lime, and one part of molybdenum oxide. The sample is then placed in a porcelain boat, covered with platinum gauze, and heated (in a quartz tube) to 200 to 250°C (392 to 482°F). The sample is then heated in steam at 850 to 950°C (1562 to 1742°F). The gases pass into 0.1 N sulfuric acid, where ammonia is chemically absorbed as ammonium sulfate and then determined by one of the usual techniques. 

In both methods it is possible to lose some of the chlorine during combustion unless necessary precautions are taken. Thoroughly mixing the coal sample with Eschka mixture and covering this carefully with additional Eschka mixture minimizes the loss of chlorine. In bomb combustion methods, the ammonium and sodium carbonate solutions in the bomb are used to absorb the chlorine as it is released in the combustion. The 10- and 15-minute waiting periods and the slow release of pressure on the bomb help to prevent the loss of chlorine as well. 

Arsenic and selenium are determined (ASTM D-4606) by mixing a weighed sample with Eschka mixture and igniting at 750°C (1382°F). The mixture is... 

Tellurium has been separated from Se after sintering the sample with Eschka mixture (1 part by weight of Na2COj + 2 parts of MgO) for 40 min at 800°C [2]. When the sinter is leached with water, the readily soluble magnesium selenate passes into solution while sparingly soluble magnesium tellurate remains in the precipitate. 

Another set of results was rejected for arsenic because of possible losses in the dry ashing ashing aids (e.g. MgO or Eschka-mixture) were indeed not added. 

Heating with Eschka-mixture (MgO/Na2CO ,) at 800°C and extraction of residue with dilute acid, followed by gravimetry ... 

Insoluble carbonaceous material remaining at this stage was converted to sulfate by fusion with Eschka mixture (MgO + Na2C03, 2 1) in a crucible at 800" C for 2 h. The filtrate was acidified, heated and sulfate was precipitated from the solution by the addition of BaCl2 to form BaS04. The precipitate was dried and weighed, and saved for isotopic analysis of sulfur in insoluble bitumen + carbonaceous residue (fraction 4 Fig. 5). 

The test for the determination of chlorine is performed by burning the coal mixed with Eschka mixture in an oxygen bomb followed by potentiometric titration with silver nitrate solution or by a modified Volhard colorimetric titration. The repeatability interval for either procedure is the same. 

ISO. 2011k. Coal and Coke—Determination of Chlorine Using Eschka Mixture (ISO 587). International Standards Organization, Geneva, Switzerland. 

A known weight of powdered coal is fused with Eschka-mixture in presence of air. The sulphur in coal is oxidised to SO2 which is absorbed by Eschka-mixture to produce the corresponding sulphites ... 

Transfer about 1 g of accurately weighed coal powder (60 mesh) to a silica, porcelain or platinum crucible. Add about 3 g of Eschka-mixture, mix thoroughly and cover with about 1 g more of Eschka-mixture. Place the crucible in a slightly slanting position in a muffle furnace at room temperature and heat gradually so as... 

The sample should be heated with Eschka-mixture at a low heat in the beginning to avoid rapid expulsion of the volatile matter which may lead to... 

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