Containment, reagents

The KEN-FLOTE column (11) is one of several column flotation processes based on a countercurrent principle. The feed slurry containing reagents is iatroduced iato the column just below the froth zone. Air is iujected at the bottom of the column via an air sparger. Wash water is sprayed within the froth zone to reject the entrained impurities from the froth. Test results on this column iadicate that a 6% ash product coal having a combustible-recovery of 75—80% can be obtained. A 70—80% pyrite reduction is also claimed. Figure 2 shows the operation of such a column. 

Note Phosphoric acid [8] and hydrochloric acid [6, 9] have both been suggested in the literature as substitutes for phthalic acid. The addition of sodium dithionite [9] is also occasionally mentioned and sometimes no additives are employed [10]. The alternative reagents offer no advantages over the phthalic acid containing reagent since they usually cause more background coloration. The limits of detection are about 0.1 —0.5 pg per chromatogram zone [5]. 

Warning of danger The perchloric acid-containing reagent should not be employed as a spray solution for reasons of safety. 

The synthetic method used to accomplish this is an indirect one known as hydroboration-oxidation. It was developed by Professor Herbert C. Brown and his coworkers at Purdue University in the 1950s as part of a broad progran designed to apply boron-containing reagents to organic chemical synthesis. The number of applications is so large (hydroboration-oxidation is just one of them) and the work so novel that Brown was a corecipient of the 1979 Nobel Prize in chemistry. 

The Preparation of Halodeoxy Sugars Using Phosphorus-Containing Reagents... 

Multi-element analyses involving solvent extraction and high performance liquid chromatography (HPLC) have also been described. The extracts, containing metal-chelate complexes with sulphur-containing reagents, such as dithizone and diethyldithiocarbamate, were used directly for determination of the metals by HPLC.14... 

Oxidation of sulphoxides to sulphones may be brought about by the use of several different bromine-containing reagents which act as a source of electrophilic bromine. To date, these reagents have not received the same attention as their chlorine analogues. 

Certain other sulfur-containing reagents also cleave methyl and other ethers see Hanes-sian, S. Guindon, Y. Tetrahedron Lett., 1980, 21, 2305 Williard, P.G. Fryhle, C.B. Tetrahedron Lett., 1980, 21, 3731 Node, M. Nishide, K. Fuji, K. Fujita, E. J. Org. Chem., 1980, 45, 4275. For cleavage with selenium-containing reagents, see Evers, M. Christiaens, L. Tetrahedron Lett., 1983, 24, 377. For a review of the cleavage of aryl alkyl ethers, see Tiecco, M. Synthesis, 1988, 749. 

For lists of reagents, with references, see Ref. 568, p. 31. For a review with respect to transition metal reagents, see Luh, T. Ni, Z. Synthesis, 1990, 89. For some very efficient nickel-containing reagents, see Becker, S. Fort, Y Vanderesse, R. Caubere, P. / Org. Chem., 1989, 54, 4848. 

Two methods, both involving boron-containing reagents, have been devised for the regioselective ortho hydroxymethylation of phenols or aromatic amines. 

The blue derivatives formed with the reagent by alkaloids remain stable for at least one day and usually much longer (cover the chromatogram with a glass plate) [2, 6, 7]. The shade of color produced can be affected by fluorescence indicators incorporated in the silica gel layer [7]. Tertiary amine alkaloids do not react at room temperature with the acetaldehyde-containing reagent [2]. 

Note The dipping solution can also be used as a spray solution. RP layers should be treated with the methanol-containing reagent on account of its better wetting properties. In addition it is necessary, particularly after the use of acidic mobile phases, to spray with alkalis, e.g. pyridine, after the heat treatment step [2, 3]. 

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