Liquid nitrogen, quenching with

The quantitative composition of liquid sulfur as determined by HPLC analysis after quenching in liquid nitrogen, extraction with C 2 and separation from the insoluble is shown in Table 3 [93]. These data are the most reliable information about the composition of liquid sulfur in the tempera-... 

During the reductive cleavage of cyclopolyenes with potassium in liquid ammonia, the intermediate anionic species are quenched with iodine-pentane mixtures. The possibility of formation of explosive nitrogen triiodide and the need for precautions are stressed. 

The reaction was so fast as to finish within 1 min, as shown by the transmission electron microscopy (TEM) images in Figure 3.3.2, for which each withdrawn sample on a copper grid was instantly quenched with liquid nitrogen and freeze-dried without melting. 

Generally, several protocols are used for the characterization of sohd-catalyzed reactions under batch reaction conditions by NMR spectroscopy. In ex situ experiments, the conversion of reactants adsorbed on the catalyst is carried out in an external oven and stopped after a given reaction time by quenching, for example, in liquid nitrogen. Subsequently, the reaction products formed on the catalyst surface are investigated at room temperature by use of a standard MAS NMR probe. This protocol is repeated with a stepwise increment of the reaction time at the same temperature or with a stepwise increment of the reaction temperature for the same duration. In an in situ experiment, the catalytic conversion of the reactants is measured inside the NMR spectrometer by use of a high-temperature MAS NMR probe. 

Fig. 2.7 (a) TEM micrograph from an /ps = 0.40, Nn = 209 PS-P2VP diblock, annealed at 140 °C for 6h then quenched in liquid nitrogen. Iodine was used to selectively stain the PVP. (b) SANS pattern from the same phase after preshearing at 140 °C (Schulz et al. 1996). (c) Possible orientations of the lam phase with respect to the shear coordinates. 

Fig. 2.25 TEM image of the HPL phase in a PS-PT dibloek with /PS = 0.68 and Mn = 40kgmol l after annealing for 6h at 145°C followed by quenching in liquid nitrogen (Khandpur et al. 1995). The PI appears dark. The inset on the left shows a section with the sample parallel to the microscope stage, the one on the right shows a magnification of the perpendicular orientation shown in the main figure.

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