Black char

Rea.ctlons, When free (R-R, R -tartaric acid (4) is heated above its melting point, amorphous anhydrides are formed which, on boiling with water, regenerate the acid. Further heating causes simultaneous formation of pymvic acid, CH COCOOH pyrotartaric acid, HOOCCH2CH(CH2)COOH and, finally, a black, charred residue. In the presence of a ferrous salt and hydrogen peroxide, dihydroxymaleic acid [526-84-1] (7) is formed. Nitrating the acid yields a dinitro ester which, on hydrolysis, is converted to dihydroxytartaric acid [617 8-1] (8), which upon further oxidation yields tartronic acid [80-69-3] (9). 

Detects all lipids by carbonization of organic material producing black charred areas. At lower temperatures ( 80°C) sterols give a purple-red... 

Chromic acid Spray the plate and heat at 180°C for All lipids give black charred spots... 

Black Charred bone, Mixture of charcoal, calcium phosphate, and... 

As the reaction propagates, the oxygen inside the porous matrix is completely consumed leaving residual char. Figure 3.11 shows a picture of smoldered polyurethane foam. The foam was ignited at the top of the sample and the reaction was allowed to propagate downward leaving a black char behind. 

Pyrolysis in inert atmosphere between 400 and yOO C produces water vapour, CO2, combustible gases CO, H2, CH and a multitude of organic vapours from the biopolymers cellulose (C6(H 0)s), hemicellulose (Cj(H20)4) and lignin. An impression of the complex product spectrum especially of the condensable organic vapours is given in Fig. 6. The remainder is a black char, mainly consisting of carbon and inorganic ash oxides. 

There is obviously an important consequence of using char absorpUvitites of 0.95-0.98 as implied in Figure 4, as opposed to using the value of 0.77 which better describes the real situation in a fire. The former will not result in as rapid heating of the sample. Rarely has much concern been shown for such important departures from near-black char surface behavior in the modeling of pyrolysis in cellulosic systems. 

A major part of the work on XPS studies on carbon has been carried out using carbon fibers and graphites because of their easy manipulation, although a few investigations have also been reported on carbon blacks, chars, and activated carbons. It is felt, however, that with the availability of the technique at different centers of carbon research, more and more work will be carried out on the analysis of surface groups on activated carbons using the technique. 

The lack of effect on total heat release, smoke and carbon monoxide, is different from halogenated flame retardants, and is taken to show that the effects are all in the condensed phase. Using gasification equipment, which duplicates the pyrolysis conditions in the cone calorimeter, without flaming taking place, Gilman and co-workers found that the melt that formed on the surface of unfilled polymer was quickly converted to a solid, black char when nano-clays were present [39]. It is postulated that this char is reinforced with nano-particles and slows down the combustion processes. It is,... 

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