Determination of the ash content

Runge hence recommended to use the easily obtained bomb values and to correct them to the true ash content by this correlation. 

Battley [58] pointed out that ash-free dry weights lead to a 5 to 6 % smaller amount of CHON-containing cell mass than determined by means of the total cellular composition. This is due to the fact that the salts of phosphorus and sulfur add a higher weight to the ash than the elements contribute to the weight of the cellular fabric. Such differences have to be taken into account when comparing caloric values of different authors. 

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For plastics, ISO 3451 Plastics — Determination of Ash describes various methods for determination of the ash content of different types of plastics including those containing glass fibres and/or flame-retardants. 

Determination of the ash content as an ess.en-tial factor for the assessment of brown coal briquettability. 

The residues at 600 °C and 800 °C are very small and relatively constant (Tables 4-69 to 4-72). They represent the inorganic part of the samples. The sample weight for thermogravimetry is only 5 mg and the experimental error is so great that exact determination of the ash content by thermogravimetry is not valid, especially for substances with ash content below 5 wt%. 

Ostromow [260] has described the analysis of mineral fillers by dry ashing (according to DIN 53568, BS 903 (1950) or ASTM D 297-59T (I960)). Determination of the ash content in polymeric compounds can be performed with standard methods Le. 

Fluidity data were determined by the Gieseler apparatus on the 16 size fractions of the medium volatile coal. The values obtained were relatively low, ranging from 8 to 81 dial divisions per minute. An attempt was made to correlate these results with petrographic data. Some of the possible relations examined are shown in Figure 4. A plot of the maceral vitrinite against fluidity shows considerable scatter as does a plot of the ash content vs. fluidity. The ash content was determined by proximate analysis (see Table I) and is included here for comparison. 

Determination of the arsenic content of each sample was performed by the AgDDC method following wet ashing. Reductive volatilization of arsenic was carried out with sodium borohydride and subsequent analysis by GC-MS. 

Mineral matter in coal is often determined indirectly with the ash analysis (determined by direct combustion of the sample) (Chapter 8) forming the basis of the calculation. However, determination and chemical analysis of the ash content of coal gives the average content of the inorganic elements in a particular coal but is not an indication of the nature or distribution of the mineral matter in coal. Nevertheless, ash analysis can provide valuable data which, when used with data from other sources, may give a representation of the mineral content of coal. 

In the lUPAC method 2.421 (Paquot, 1979a), the yellow phosphovanadomolybdic complex is used for the determination of the phosphorus content of oils and fats. The lUPAC method also differs on other points the oil is ignited in the presence of magnesium oxide and the ash is dissolved in nitric acid. 

Y. Nakahara and H. Sekine, Studies on confirmation of cannabis use. I. Determination of the cannabinoid contents in marijuana cigarette, tar, and ash using high performance liquid chromatography with electrochemical detection, J. Anal. Toxicol., 1985, 9, 121-124. 

AS 2836.11-1998. Methods of testing surgical dressings surgical dressing materials — Method for the determination of sulfated ash content. 

At the end of this section an essential caveat should be kept in mind. Caloric values less than 17.6 kJ/g afdw should be considered with suspicion. Carbohydrates bum with the lowest energy content of 17.6 kJ/g, proteins and lipids with higher values (see Table 1). Combustion heats lower than 17.6 kJ/g afdw may be due to a wrong determination of the ash fraction or to contributions of inorganic reactions during burning (see e.g. [37]). 

The ash content of furnace blacks is normally a few tenths of a percent but in some products may be as high as one percent. The chief sources of ash are the water used to quench the hot black from the reactors during manufacture and for wet pelletizing the black. The hardness of the water, and the amount used determines the ash content of the products. The ash consists principally of the salts and oxides of calcium, magnesium, and sodium and accounts for the basic pH (8—10) commonly found in furnace blacks. In some products potassium, in small amounts, is present in the ash content. Potassium salts are used in most carbon black manufacture to control stmcture and mbber vulcanizate modulus (22). The basic mineral salts and oxides have a slight accelerating effect on the vulcanization reaction in mbber. 

As microwave sample preparation has evolved, standard microwave procedures have been developed and approved by numerous standard methods organisations (ASTM, AOAC International, EPA, etc.), see ref. [64]. Examples are standard test methods for carbon black/ash content (ASTM Method D 1506-97), lead analysis in direct paint samples (ASTM Method E 1645-94), etc. Table 8.15 shows some microwave ashing references (detection weight). A French AFNOR method utilises the atmospheric pressure single-mode microwave method as an alternative sample preparation procedure for Kjeldahl nitrogen determination [84], The performance of a microwave-assisted decomposition for rapid determination of glass fibre content in plastics for QC has been described [85]. 

Two methods were used to determine the purity of the final material. The ash content was obtained by calculation of a weight loss of 1 g size graphite sample, after its exposure to 900°C for 4 hours (Superior Graphite AIMS procedure FBQ0001). This test gives a good idea of the total amount of impurities. The nature of impurities and their specific concentrations as measured in ppm or ppb levels, was determined with an ICP inductively coupled plasma spectrometer (Model Jobin Yvon Ultima POXX/681,... 

Table 21 reports the ash content and ash composition (determined by inductively coupled plasma-atomic emission spectroscopy, ICP-AES) for all of the calcined cokes used to fabricate the test graphites. It can be seen that the amount of ash and its make-up are variable, but are within the range observed for petroleum-based calcined cokes. Although the ash contents in all of the calcined cokes appear rather high, these materials may still be acceptable because many of the metallic species are driven off during graphitization. This aspect is addressed in the next section. 

Studies of the inorganics in cotton dust have incorporated the use of a wide variety of techniques. These include X-ray fluorescence spectroscopy, atomic absorption spectroscopy, electron microscopy, energy dispersive analysis of X-rays, X-ray diffraction, atomic absorption spectroscopy, neutron activation analysis and petrographic microscopy. It is necessary to use a wide array of techniques since no single technique will permit the measurement of all trace elements. Steindard chemical techniques to determine the ash content of samples and of various extracts have also been used. In most of these studies the ash fraction has been considered to be a reasonably accurate measure of the inorganic content. 

Two bituminous coals of moderate ash content were chosen for this paper to illustrate this method of determining coal-mineral association. The first sample was an Upper Freeport coal with 1.3% moisture, 9.88% ash, and 1.56% total sulfur. The second sample was an Indiana No. 3 coal having 10.5% moisture, 7.35% ash, and 4.26% total sulfur. Both coals had been precleaned at a coarse particle size, ground to minus 325 mesh (44 ym), and then separate samples were cleaned by float-sink and by froth flotation techniques, as described elsewhere [5]. Analyses of the feed coals are included in Table I. 

Previous work on superplasticized Portland cement concrete containing fly ash or blast furnace slag has shown that such mixes require 10% less admixture than reference Portland cement concrete to attain the same workability. Therefore, a given dosage may produce higher water reduction. The reason for the reduced admixture requirement has not been determined. It is probably due to the lowering (dilution) of the C3A content... 

The mineral content of foods is usually determined from the ash prepared by heating a sample at 500-600°C in a muffle furnace for about 4h to oxidize organic matter. The ash does not represent the salts as present in the food because ... 

Hie coal was ground in the laboratory and sized to pass 200 mesh. Ash determinations on tne ground coal sample were made, and an average value of 5.2% was used to correct for the ash content of the extracted coals. 

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