Carbon and hydrogen

Carbon and hydrogen are. determined by burning a weighed quantity of coal, in presence, of CuO, in a stream of oxygen free from moisture and CO2. The carbon and hydrogen of the sample are converted into CO2 and H2O  

Dumas introduced the oxidation method in which a mixture of nitrogen-containing organic material and copper oxide is heated in an inert atmosphere to form carbon dioxide, water, and nitrogen. The carbon dioxide is absorbed, the water condensed, and the nitrogen determined volu-metrically. Although the Dumas method has been employed for many years, various modifications have been made to increase the accuracy and the precision. 

The gasification method consists of mixing the coal for coke 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°C-250 C (390°F-480°F). The sample is then heated in steam at 850°C-950°C (1560°F-1740°F) depending on whether the sample is coal or coke, respectively. The gases pass into a solution of 0.1 N sulfuric acid where the ammonia is absorbed and determined by one of the usual techniques. 

The standard procedure in many laboratories is the Kjeldahl method (ASTM, 2011s ISO, 2011c,d), although there are the standard methods which involve the Dumas technique (DIN, 2011a) 

Sulfur is present in coal either as organically bound sulfur or as inorganic sulfur (pyrite or marcasite and sulfates) (Kuhn, 1977). The amount of organic sulfur is usually 3% w/w of the coal, but exceptional amounts of sulfur (up to 11%) have been recorded. The sulfates (mainly calcium and iron) rarely exceed 0.1% except in highly weathered or oxidized samples of coal pyrite and marcasite (the two common crystal forms of FeS2) are difficult to distinguish from one another and are often (incorrectly) designated simply as pyrite. 

Sulfur is an important consideration in coal utilization and, hence, there is a considerable amount of published work relating to the development of methods to improve the efficiency of the techniques as well as to improve the accuracy and precision of the sulfur determination (Ahmed and Whalley, 1978 Chakrabarti, 1978a Attar, 1979 Raymond, 1982 Gorbaty et al., 1992). 

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Hydrocarbons constitute the essential components of petroleum their molecules contain only carbon and hydrogen they are grouped into many chemical families according to their structure. All structures are based on the quadrivalency of carbon. 

Molecules in this category contain atoms other that carbon and hydrogen. The distinction is made between organic and organometallic compounds. 

The analyst now has available the complete details of the chemical composition of a gasoline all components are identified and quantified. From these analyses, the sample s physical properties can be calculated by using linear or non-linear models density, vapor pressure, calorific value, octane numbers, carbon and hydrogen content. 

I. Carbon and Hydrogen. The presence of these elements is usually assumed. If a direct test is required, a mixture of about 01 g. of the powdered substance and 2-3 g. of finely powdered copper oxide is heated in the tube A (Fig. 68) and the... 

After some experience, an able student will find that it is frequently unnecessary to carry out all the Tests A—L. If, for example, the substance is found to contain only carbon and hydrogen, and chars on ignition giving a smell of burnt sugar, then confirmatory tests (given in... 

The furnace. For heating the tube packing, a small electric furnace E is used, similar to that described in the carbon and hydrogen determination. It is 22 cm. in length and 1 5 cm. in diameter. The furnace is maintained at 680 C., as before, by a calibrated Simmerstat and its temperature is checked from time to time with a bimetal pyrometer. 

We have also added an entirely new section dealing with semi-microanalysis. In our original Introduction (p. ix) we justified the retention of macro-methods of quantitative analysis on the grounds that they formed an excellent introduction to micromethods and also afforded a valuable training in exact manipulation generally. By now, however, the macro-estimation particularly of carbon and hydrogen and of nitrogen has disappeared entirely from most laboratories. On the other hand, the micro-... 

If it is desired to test directly for the presence of carbon and hydrogen in a compound, mix 01 g. of the substance with 1-2 g. of ignited, fine... 

Chemists make compounds and strive to understand their reactions. My own interest lies in the chemistry of the compounds of the elements carbon and hydrogen, called hydrocarbons. These make up petroleum oil and natural gas and thus are in many ways essential for everyday life. They generate energy and heat our houses, fuel our cars and airplanes and are raw materials for most manmade materials ranging from plastics to pharmaceuticals. Many of the chemical reactions essential to hydrocarbons are catalyzed by acids and proceed through positive ion intermediates, called carbocations. 

Molecular formulas of organic compounds are customarily presented in the fashion C2H5Br02 The number of carbon and hydrogen atoms are presented first followed by the other atoms in alphabetical order Give the molecular formulas corresponding to each of the compounds in the preceding problem Are any of them isomers ... 

The general molecular formula for an alkene is Cr,H2n Ethylene is C2H4 propene IS C3H6 Counting the carbons and hydrogens of the compound shown (CsHie) reveals that it too corresponds to CnH2n... 

Recall from Section 2 19 that reduction corresponds to a decrease in the number of bonds between carbon and oxygen or an increase in the number of bonds between carbon and hydrogen (or both)... 

Bond line formula (Section 1 7) Formula in which connec tions between carbons are shown but individual carbons and hydrogens are not The bond line formula... 

In gas-solid extractions the sample is passed through a container packed with a solid adsorbent. One example of the application of gas-solid extraction is in the analysis of organic compounds for carbon and hydrogen. The sample is combusted in a flowing stream of O2, and the gaseous combustion products are passed through a series of solid-phase adsorbents that remove the CO2 and 1T20. 

Chemistry. In direct combustion coal is burned to convert the chemical energy of the coal into thermal energy, ie, the carbon and hydrogen in the coal are oxidized into carbon dioxide and water. 

Dowtherm J is a mixture of isomers of an alkylated aromatic that contains only carbon and hydrogen. Dowtherm J can be used in Hquid-phase systems at temperatures as low as —73° C and in vapor-phase systems at temperatures from 185 to 315°C. Dowtherm Q is a mixture of diphenylethane and alkylated aromatics intended for Hquid-phase systems. It can be used at temperatures as low as —34°C. Dowtherm HT is a mixture of hydrogenated terphenyls intended for Hquid-phase systems. Dowtherm HT and Therminol 66 are essentially identical. 

Hydrocarbons, compounds of carbon and hydrogen, are stmcturally classified as aromatic and aliphatic the latter includes alkanes (paraffins), alkenes (olefins), alkynes (acetylenes), and cycloparaffins. An example of a low molecular weight paraffin is methane [74-82-8], of an olefin, ethylene [74-85-1], of a cycloparaffin, cyclopentane [287-92-3], and of an aromatic, benzene [71-43-2]. Cmde petroleum oils [8002-05-9], which span a range of molecular weights of these compounds, excluding the very reactive olefins, have been classified according to their content as paraffinic, cycloparaffinic (naphthenic), or aromatic. The hydrocarbon class of terpenes is not discussed here. Terpenes, such as turpentine [8006-64-2] are found widely distributed in plants, and consist of repeating isoprene [78-79-5] units (see Isoprene Terpenoids). 

Polymerization and GycliZation. Acetylene polymerizes at elevated temperatures and pressures which do not exceed the explosive decomposition point. Beyond this point, acetylene explosively decomposes to carbon and hydrogen. At 600—700°C and atmospheric pressure, benzene and other aromatics are formed from acetylene on heavy-metal catalysts. 

In the Sabatier reaction, methane and water are formed over a nickel— nickel oxide catalyst at 250°C. The methane is recovered and cracked to carbon and hydrogen, which is then recycled ... 

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