Char, blackening

Tartaric acid and tartrates also swell up, blacken and give an odour resembling burnt sugar. Citrates and lactates also char, and give off odours resembling burnt sugar. 

The first trend involves the "blackening" of the char while discrete absorptions decline in intensity as the temperature is increased, an IR continuum grows and begins to level off above about 700°C. The explanation, briefly, is that as the material is pyrolized, polyaromatic networks grow and tend in structure toward that of graphite. Following Kmeto [ 1J], the band gap... 

Treat with cone, sulphuric acid. Pure glucose does not char in the cold on heating a yellow colour is developed which gradually darkens (cf. cane sugar). Ordinary commercial glucose is impure and blackens readily on heating. 

Alexander felt a burning fever take hold of him, but it was only Dusha s soft arms. Somewhere above him, drowning out the horses, the cries of his sisters and his Papa, as well as the thunderous roar of flames, all he could hear were Dusha s raw, choking sobs and the rabid screams of the stranger. The stranger who finally pitched over, a charred and blackened skeleton. 

Contrary to expectations, small quantities of char were collected after each experiment. Soot formation was evident, and particularly prominent following the corn cob experiment. Coking of the volatile matter on the reactor wall beneath the window rendered the lower part of the reactor opaque. The water condensate was a light yellow color with a disagreeable (but not strong or particularly foul) odor. No tar was observed in the condenser, but the teflon tube connecting the reactor to the condenser was blackened. 

Properties. — Radium is a white metal, with a melting point of about 700°. It blackens rapidly in the air due to the formation of the nitride. It chars paper, and reacts readily with water, forming the hydroxide. It dissolves easily in HC1. The element displays all the phenomena of radioactivity which are characteristic of its salts. On this account it is customary to speak of the amount of radium element present in a compound... 

Char (1, n) n. Animal or vegetable carbon black used as a decolorant in the process industries (2, v). To partly burn and blacken, especially the outside surface of a carbonaceous material. 

The collapse of the cellulose structure near 300 °C results in a mixture of predominantly aliphatic materials that dominates up to about 400 °C, but then is replaced by a predominantly aromatic counterpart. The extent of the latter decreases as the temperature increases, and the IR bands of discrete species decline and disappear near 700 °C. Polyaromatic structures continue to grow, as evidenced by the continued IR blackening as the charring proceeds. 

During the Spalik study of Sn transport by rosin, the rosin was observed to change in color from light amber to a very pale, transparent yellow as a liquid and became a light yellow solid upon cooling. It could be remelted and held between 3 50 ° C and 400 ° C for several hours without a visible change if a N2 flow was maintained, but charred and blackened quickly if the N2 flow was... 

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