Eschka method

Calcium was determined by an EDTA method carbon and hydrogen by the combustion method total nitrogen by the Kjeldahl method sulfur by the Eschka method infrared spectra by the potassium bromide pellet technique. 

Ultimate analysis of coal and coke, determination of total sulfur content, Eschka method Ultimate analysis of coal and coke, determination of total sulfur content, high temperature combustion method... 

The three most widely used test methods for sulfur determination are (1) the Eschka method, (2) the bomb washing method, and (3) the high-temperature combustion method, and all are based on the combustion of the sulfur-containing material to produce sulfate, which can be measured either gravimetrically or vol-umetrically. The Eschka method has distinct advantages in that the equipment... 

Analytical Procedures. The samples of bituminous coals were analyzed for pyritic sulfur, sulfate sulfur and total sulfur using conventional wet chemical procedures adapted from the American Society of Testing Materials (23, 24). The ASTM D 3177-75, The Eschka method was used for the total sulfur, and ASTM D-2492-79was used for sulfate and pyritic sulfur determinations. The treated samples were filtered through a Whatman 2 filter paper to separate the coal particles from the liquid medium. The filtered sample was washed with 0.1 N HCl followed by distilled water to remove traces of absorbed sulfate and iron. 

The total sulfur content of the coal samples was determined by the Eschka method. The sulfate sulfur content of the test samples was determined by extraction of a one-gram sample with dilute hydrochloric acid followed by turbidimetric determination of sulfate (24). The pyritic sulfur content was determined by extraction of the weighed coal samples with 2N nitric acid followed by titrimetric or atomic absorption determination of iron in the extract. (25). 

The concentrations of alkali metals and chlorine were determined directly for the fuel samples using a inductively coupled plasma-atomic emission spectrometry apparatus in order to analyse sodium and potassium contents. Chlorine content was determined by Eschka method according to ASTM D2361-66. The concentrations are given on dry basis (table 1). 

Ignition for 2 h at 800°C (Eschka method) and extraction of residue with water, followed by ICP-AES detection ... 

The results of experiments with ten coals from different localities are shown in Table II. For a comparative study, the total chlorine content of each coal sample was also determined by the Eschka method. 

The Eschka method for the determination of sulfur originated more than 100 years ago and has been accepted as a standard method in several conntries. The method has distinct advantages in that the equipment is relatively simple and only the more convenient analytical techniques are employed. 

ISO. 201 le. Coal and Coke—Determination of Total Sulfur, Eschka Method (ISO 334). International Standards Organization, Geneva, Switzerland. 

The total sulfur content may be determined by one of several methods that convert it to sulfate by wet chemical analysis. One of these, the Eschka method, involves combustion of coal at 800°C in the presence of alkaline/oxidant medium (e.g., two parts of calcined MgO and one part anhydrous sodium carbonate) all sulfur is converted to sulfate that by the addition of barium chloride precipitates as barium sulfate, which is calcined to BaO and measured gravimetrically (see ASTM D3177). This is a standard method in many countries. Another is the high-temperature method where the coal is burned in oxygen at 1350°C, converting all sulfur present into SO2. The SO2 is then converted to sulfuric acid for titrimetric determination. 

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. 

The gravimetric determination of sulfate can be and is most often used to finish the Eschka and bomb washing methods. The most serious concern is that the barium sulfate precipitated may be extremely fine and difficult to filter. This can be overcome by adding the barium chloride (BaCE) rapidly to the hot solution and stirring the mixture vigorously to obtain a barium sulfate (BaS04) precipitate,... 

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. 

A modification of the oxygen bomb combustion method (ASTM D-2361) for the determination of chlorine consisted of acidifying a solution of the adsorbed combustion products and titrating the chlorine potentiometrically. A potentio-metric titration was also tried for the determination of chlorine by the oxygen flask method. Combustion products, including chlorine, were absorbed in sodium hydroxide (NaOH), and the chloride was measured using silver-silver chloride electrodes. Although there was no statistical difference in results obtained from potentiometric titration and the Eschka procedure, the latter was more precise. 

Sulfur in coal that is burned to generate electricity is a major source of acid rain and SO2 air pollution. In Eschka s method to measure S, coal is fused with 5 times its mass of a 2 1 (by mass) mixture of MgO and anhydrous Na2C03 at 800°C for 4 h in air. Sulfur ends up as sulfate (SO ) and sulfite (SOf") salts. The fused mass is dissolved in 6 M HCl and boiled with aqueous Br2 to oxidize S03 to SO . Excess Br2 is evaporated. The solution is adjusted to pH 3 and aqueous BaCl2 is added to precipitate BaS04, which is filtered, washed, dried by ignition, and weighed. 

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