Nitrogen elemental, determination

It is apparent from Table IV that trace elements determined by the x-ray fluorescence method are limited to those occurring in whole coals at concentrations of at least a few parts per million. Elements such as selenium, mercury, and antimony, which are generally present in whole coal at levels below 1 ppm, cannot be determined by this method. The major elements in coal, hydrogen, carbon, oxygen, and nitrogen, cannot be determined by x-ray fluorescence, but this should not inhibit the use of the method for trace and minor element determinations. 

We have used the ESCA results to provide empirical information about the apparent stoichiometry of sulfate, ammonium, and nitrate ions and other elements and species. Wet chemical analyses performed at several laboratories seemed to contradict some of the conclusions reached from ESCA studies. For example, total reduced nitrogen as determined by ESCA often agrees with the determination of ammonium by wet chemical methods. A consequence of this discrepancy is that in analyses where wet analysis would indicate ammonium sulfate, ESCA would suggest ammonium bisulfate, based on the assumption that particulate Nx species are not associated with sulfate. This assumption may not be valid, because it has been demonstrated QJ that a large fraction of Nx present... 

For phytoplankton particulate organic carbon (POC) and particulate nitrogen (PON) determination, some suspended matter was collected on precombusted (450°C) Whatman GF/F filters, dried at 60°C and stored in polystyrene Petri dishes until analysis. POC and PON were analyzed with a Carlo Erba NA 2000 elemental analyzer. The analytical error of the... 

Elemental Analyses. Carbon, hydrogen, and sulfur were determined gravi-metrically as carbon dioxide, water, and barium sulfate, respectively. Nitrogen was determined by a micro-Dumas method. Oxygen was determined by difference. 

Table 3.4 The composition of typical end-member particles from the Clyde and Humber. Fe and Mn were determined following extraction by hydroxylamine hydrochloride-acetic acid. Carbon and nitrogen were determined using an elemental analyser. Specific surface area (SSA) was determined using a BET nitrogen adsorption technique (nd = not determined). REM and MEM denote river and marine end-members, respectively.

Ethylene dimethacrylate (5.64 g), methacrylic acid (0.52 g 6.0 mmol), L-phenylalanine anilide (0.25 g 1.5 mmol), and of AIBN (W mg) in acetonitrile 98.2 mL) were mixed in a glass tube. After degassing, the tube was sealed under nitrogen and consecutively heated for 24 h each at 60, 90, and 120 °C. Subsequently, the polymer was ground and subjected to continuous extraction in acetonitrile for 24 h. To determine the recovery of imprint molecules, the extracted anilide was quantitatively determined and the polymer was investigated by nitrogen elemental analysis before and after extraction of the imprint molecule. According to these methods about 90% of the imprint molecules had been removed from the polymers. 

The composition of the isolated copolymer was determined from (a) the nitrogen elemental analysis, and (b) the sulfur elemental analysis. Both figures were corrected for the small amount (4-12%) of water associated with the polymer. 

In routine use, element determinations can be used to check the surface saturation and scale-up without the need for strict dose control makes the process facile. The pressure of the reaction chamber had no effect on the surface saturation, which is as expected since the saturation density is determined by the number of bonding sites and the energy available to produce chemisorption to these sites. The transport of the reactant into the reaction chamber is determined by the vapour pressure, and the flow rate of the vapour to the support bed. Once the reactant is inside a pore it will continue to react so long as bonding sites are still available. The same surface saturation was achieved by using three different reactor set-ups and either a lower pressure of 6-10 kPa or ambient pressure in nitrogen flow. 

The same situation is met in R-M-N ternary nitrides in which the nature of the M element determines the dominating type of bond involved in the material. This is illustrated by the fact that with lithium (or barium) as a cationic element, the R-M-N corresponding nitride is essentially ionic in character, whereas with silicon, more covalent nitrido-silicates are formed. In addition, metallic nitrided alloys exist, with nitrogen located as an interstitial element in octahedral voids of the metal atom lattice. The presence of insertion nitrogen (as well as carbon) in such compounds is sometimes necessary for their existence, and can strongly modify the physical properties. 

The magnitude of effort required is illustrated by the classic work on zone-refined aluminum by Albert of the CNRS Laboratory in Paris. Samples were analyzed for over 60 elements plus the rare earths by high-sensitivity neutron activation using detailed radiochemical procedures. Elements such as carbon, oxygen, and nitrogen were determined by photonuclear or charged-particle activation. This procedure required the efforts of a four-man team for 12 hr, an additional person for nine days, and another person for two weeks to analyze the rare earths. After the amounts of individual contaminants were totaled (for many there were only experimental upper limits of 1-10 ng), it was possible to establish that a particular sample of aluminum contained less than 2 ppm total impurities (i.e., it was not quite 6-9 s pure). 

The determination of the elemental composition of a petroleum cut is of prime importance because it provides a quick means of finding out the quality of a given cut or determining the efficiency of a refining process. In fact, the quality of a cut generally increases with the H/C ratio and in all cases, with a decrease in hetero-element (nitrogen, sulfur, and metals) content. 

The physical and mechanical properties of steel depend on its microstmcture, that is, the nature, distribution, and amounts of its metaHographic constituents as distinct from its chemical composition. The amount and distribution of iron and iron carbide determine most of the properties, although most plain carbon steels also contain manganese, siUcon, phosphoms, sulfur, oxygen, and traces of nitrogen, hydrogen, and other chemical elements such as aluminum and copper. These elements may modify, to a certain extent, the main effects of iron and iron carbide, but the influence of iron carbide always predominates. This is tme even of medium alloy steels, which may contain considerable amounts of nickel, chromium, and molybdenum. 

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