Laurence Rodier

Dissociation Constants of Protonated Amines in Water at Temperatures from 293.15 K to 343.15 K

The dissociation constants of protonated 2-amino-1-ethanol (MEA), diethanol amine (DEA), triethanol amine (TEA), methyldiethanol amine (MDEA), 2-amino-2-methyl-1-propanol (AMP), 3-dimethylamino-1-propanol (DMAP), tris(hydromethyl)aminomethane (THAM), 2-[2-(dimethylamino)ethoxy]ethanol (DMAEOE) and, 1,2-bis(2-aminoethoxy)ethane (DiAEOE) were determined in the temperature range 293.15 to 343.15 K using a potentiometric titration method. The experimental technique was first validated using as reference the available literature data of MDEA. The dissociation enthalpies of amines were derived from their dissociation constants using the Van’t Hoff equation. Experimental dissociation constants and dissociation enthalpies were discussed in term of amine structure and compared with literature values when available.

Determination of growth and maintenance coefficients by calorespirometry

This study describes a calorespirometric method for determining the coefficients of the correlation of specific respiration and growth rates. To validate the calorespirometric method, coefficients obtained from calorespirometric data are compared with coefficients obtained from mass and elongation growth rates measured at three temperatures on oat (Avena sativa L.) shoots. Calorespirometric measurements were also made on leaf tissue of varying age from Verbascum thapsus L., Convolvulus arvensis L., and Helianthus tuberosus Nutt. Measurements on A. sativa, C. arvensis and H. tuberosus at several temperatures show maintenance coefficients generally increase with temperature, but, in disagreement with accepted theory, growth coefficients for C. arvensis and A. sativa vary with temperature. A comparison of rates expressed as intensive and extensive quantities showed that the decline in specific respiration and growth rates with age is caused by dilution-by-growth, not down-regulation of respiration rate by reduced demand. The ratio of heat rate to CO2 rate increases with leaf age, and, for fully mature leaves, exceeds the maximum possible value for carbohydrates. This shows that the catabolic substrate may vary with leaf age in immature leaves and cannot be assumed to consist only of carbohydrates in mature leaves. Dilution-by-growth, substrate variation, and inseparability of the variables in the growth-maintenance model all complicate physiological interpretation of the slope and intercept of plots of specific respiration rates v. specific growth rates.