Halogen analysis

Sulfur in an organic compound is converted into sulfate ion by the methods used in halogen analysis (Sec. 2.26) treatment with sodium peroxide or with nitric acid (Carius method). This is then converted into barium sulfate, which is weighed. 

Interest in the use of reducing agents to activate C-F bonds was revived when systems that enabled selective removal of fluoride from perfluorocarbons were discovered in contrast to the complete (destructive) removal of halides as in sodium fusion reactions employed in methods for halogen analysis [31]. (Interest in this latter area has also had resurgence in the search for methods capable of destroying chlorofluorocarbons [32].) The key breakthrough was the report by MacNicol and Robertson that hexakis(thiophenoxy)napthalene can be prepared by treatment of perfluorodecalin with excess sodium phenylthiolate for 10 days at 70°C in DMF [33]. 

For halogen analysis, the combustion product contains HX (X = Cl, Br, I). HX is trapped in water and titrated with Ag ions by an automated electrochemical process. 

Qualitative analysis for the elements. This includes an examination of the effect of heat upon the substance—a test which inter alia will indicate the presence of inorganic elements—and quahtative analysis for nitrogen, halogens and sulphur and, if necessary, other inorganic elements. It is clear that the presence or absence of any or all of these elements would immediately exclude from consideration certain classes of organic compounds. 

Chlorine and bromine add vigorously, giving, with proper control, high yields of 1,2-dihaloethyl ethers (224). In the presence of an alcohol, halogens add as hypohaUtes, which give 2-haloacetals (225,226). With methanol and iodine this is used as a method of quantitative analysis, titrating unconsumed iodine with standard thiosulfate solution (227). 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

Volatile impurities, eg, F2, HF, CIF, and CI2, in halogen fluoride compounds are most easily deterrnined by gas chromatography (109—111). The use of Ftoroplast adsorbents to determine certain volatile impurities to a detection limit of 0.01% has been described (112—114). Free halogen and haHde concentrations can be deterrnined by wet chemical analysis of hydrolyzed halogen fluoride compounds. 

J. E. Ellis and G. Iveson, The Application of Gas-Eiquid Chromatography to the Analysis of Volatile Halogen and Interhalogen Compounds, Gas Chromatography, Butterworths, London, 1956 pp. 300—309. 

It is possible to use halogen-sensitive detectors in glc analysis of active hydrogen compounds by sdylating them with a halogenated sdylating agent, eg, CMDMS (9). 

Analysis for boron, haUde, free halogen, and siUcon is carried out by standard methods following hydrolysis of BX (11,79). Specifications for BCl and BBr supphed by Kerr-McGee Corp. are given in Table 2. 

Benz[e][ 1,2]azaborine, 1,2-dihydro-2-methyl-halogenation, 1, 656 Benz[6]- 1-azafulvenes dimerization, 4, 309 Benz[c]-2-azafulvenes dimerization, 4, 309 Benzazatropolone X-ray analysis, 7, 494 1 -Benzazepine, N-acetyl-6-hydroxy-bromination, 7, 528... 

The composition of an oil and the progress of its hydrogenation is expressed in terms of its iodine value (IV). Edible oils are mixtures of unsaturated compounds with molecular weights in the vicinity of 300. The IV is a measure of this unsaturation. It is found by a standardized procedure. A solution of ICl in a mixture of acetic acid and carbon tetrachloride is mixed in with the oil and allowed to reac t to completion, usually for less than I h. Halogen addition takes place at the double bond, after which the amount of unreacted iodine is determined by analysis. The reaction is... 

Halogen, sulphur, nitrogen content Ash content Analysis of ash Organic content by BOD, COD, PV or total carbon methods completed... 

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