Sulfur qualitative identification

Qualitative Identification of the Sulfur Croups. Tests of polymers with a known structure were used to identify the temperature at which each sulfur group releases its sulfur. Four polymers were tested ... 

Qualitative Analysis. ESCA is readily applied to the qualitative identification of elements present in a sample surface, to depths of 25 A for metals and up to 100 A for polymers. All elements except hydrogen and helium can be determined with the typical X-ray source. The XPS spectra for sulfur obtained with monochromated A1 K radiation and MgK radiation are presented in Figs. 14.9 and 14.10, respectively. Each spectmm... 

It is of interest to examine the development of the analytical toolbox for rubber deformulation over the last two decades and the role of emerging technologies (Table 2.9). Bayer technology (1981) for the qualitative and quantitative analysis of rubbers and elastomers consisted of a multitechnique approach comprising extraction (Soxhlet, DIN 53 553), wet chemistry (colour reactions, photometry), electrochemistry (polarography, conductometry), various forms of chromatography (PC, GC, off-line PyGC, TLC), spectroscopy (UV, IR, off-line PylR), and microscopy (OM, SEM, TEM, fluorescence) [10]. Reported applications concerned the identification of plasticisers, fatty acids, stabilisers, antioxidants, vulcanisation accelerators, free/total/bound sulfur, minerals and CB. Monsanto (1983) used direct-probe MS for in situ quantitative analysis of additives and rubber and made use of 31P NMR [69]. 

The SEM is also used to do X-ray/elemental analysis. This technique is qualitative. X-ray analysis and mapping of the particular elements present is useful for the identification of inorganic fillers and their dispersion in compounds as well as inorganic impurities in gels or on surfaces and curatives, e.g., aluminum, silicon, or sulfur in rubber compounds and Cl and Br in halobutyl blends. (Figure 9)... 

Qualitative Analysis. High-resolution MS generally can separate and identify the formulas of essentially all heteroaromatic components containing one or more oxygen, sulfur, and nitrogen atoms per molecule, although some difficulties remain in the routine identification of sulfur compounds. The approach used to compensate for the latter difficulty is discussed in the section on quantitative analysis. 

Qualitative methods for the identification are given in Table 15. Quantitative methods are well documented. Sulfur compounds are readily studied by vibrational spectroscopy, both IR and Raman. The oxides and oxyanions have characteristic spectra in the IR while the sulfanes and cyc/o-sulfur compounds give strong Raman spectra as a result of their high polarizability. The only potentially useful NMR nucleus is S, which is quadrupolar and low in abundance (Table 2). In general, measurements of NMR... 

The elemental composition is useful for characterisation of inorganic pigments and organic dyes. However, a database is needed for their identification. In all ballpoint pen inks, sulfur, copper, silicon and phosphorus are present in the elemental composition. Some samples also contain zinc, chlorine, bromine and calcium. In black inks, chromium and lead are additionally found. Samples differ with respect to the elemental composition quantitatively rather than the qualitatively. A greater variability in elemental content is observed for gel inks. 

The previously described simple screening tests are not always sufficient to identify an unknown plastic with certainty. In some cases the use of chemical reactions for identification purposes cannot be avoided. First, one tests for heteroatoms, those elements which are present in the plastic in addition to carbon and hydrogen, such as nitrogen, sulfur, chlorine, fluorine, silicon, and sometimes phosphorus. Unfortunately, there is no simple direct method for the certain identification of oxygen, so it is not possible to test for oxygen in a qualitative manner. The following reactions presuppose a certain amount of experimental skill and the necessary care. 

A qualitative test for aromatic and heteroaromatic compounds is their solubility in concentrated sulfuric acid (Shriner, R. L. Fuson, R. C. and Curtin, D. Y. The Systematic Identification of Organic Compounds Wiley New York, 1956. Another precedent is the H-D exchange of thiophene by dissolving the latter in concentrated D2SO4. 

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