The global kinetics of the oxidation and removal of copper(0) foil were examined in liquid and supercritical CO2 using tert-butyl peracetate (t-BuPA) as the oxidant and dialkyldithiocarbamate lithium salts (Li+R2DTC-, with R = ethyl, propyl, or n-butyl) as the chelating agent. The pressure was kept constant (at 240 bar) for all reactions as density was not found to affect the kinetics at pressures above 150 bar. Temperature was varied between 25 and 60 degrees C and the concentrations of the oxidant and chelating agents were varied to determine the observed overall reaction orders for each species. Interestingly, under our reaction conditions, the observed global reaction was independent of oxidant concentration but varied due to the R2DTC- concentration. The Et2DTC- had an observed half order reaction dependence, indicating a complex reaction mechanism while the other two R2DTC- had first order dependence suggesting diffusion limitations. Arrhenius expressions were determined by the temperature dependent kinetics of the product, Cu(R2DTC)(2), formation. The apparent activation energy, E-a, for the Et2DTC- was 66 kJ/mol, confirming a complex reaction mechanism due to its large value. The apparent activation energies for the Pr2DTC- and Bu2DTC- were 14 and 17 kJ/mol, respectively. These low energies are consistent with diffusion limitation.

An investigation was conducted on an Olivier silt loam (fine‐silty, mixed, thermic aquic, Fragiudalfs) at two locations to determine the influence of 6 seasonal temperatures and 4 N rates on head diameter, head weight, tissue NO3 concentration and crop yield of 4 head lettuce (Lactuca sativa L.) cultivars. An analysis of covariance was used to establish prediction equations for each dependent variable. Temperature was shown to have a significant curvilinear influence on all crop parameters. There was a significant cultivar X temperature interaction with respect to all dependent variables except tissue NO3 concentration. Calculated optimum mean temperatures for maximum head diameters, head weights, and yields for all cultivars were found to range between 17.4° and 18.2°C. Fertilizer N effects were significant on head weight and crop yield. Nitrogen rate did not significantly affect young leaf tissue N03 concentration. Greater tissue NO3 levels were found at lower temperatures in the covariate range. At optimum temperatures, the cultivar ‘Fairton’ produced larger diameter heads and greater yields.