Vaporization, heat complement

Thermochemical data were required for the estimation of ground state strain. Heats of formation ( 0.5 kcal mol-1) were obtained by the experimental determination of heats of combustion 25 -27) using either a stirred liquid calorimeter 25) or an aneroid microcalorimeter 26) heats of fusion and heat capacities were measured by differential scanning calorimetry (DSC), heats of vaporization 21, 25, 27) by several transport methods, or they were calculated from increments 28). For the definition of the strain enthalpies Schleyer s single conformation increments 29) were used and complemented by increments for other groups containing phenyl30) and cyano substituents. 

More recently, atmospheric pressure photoionization (APPI) has been introduced [181] as a complement or alternative to APCI [176,182,183]. In APPI, aUV light source replaces the corona discharge-powered plasma, while the pneumatic sprayer and the heated vaporizer remain almost unaffected (Fig. 12.43) [184-186]. The most relevant modification is the use of a quartz tube to guide the hot vapor toward the sampling orifice. Quartz is required to transmit the UV light emitted by a noble gas discharge lamp. 

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