Diarrhea in neonates is often complicated by metabolic acidosis. We used blood gas analysis and HPLC to determine whether bacterial fermentation might contribute to acidosis in diarrheic calves. Diarrheic calves (n = 21) had significantly lower pH, PCO(2), HCO(3)(-) and a higher anion gap than healthy calves (n = 21). Serum concentrations (mean +/- SD, mmol/L) of DL-, L- and D-lactate were also significantly higher in diarrheic (8.9 +/- 5.1, 4.1 +/- 3.4 and 5.2 +/- 5.7) than in healthy calves (1.7 +/- 1.2, 2.0 +/- 1.1 and too low to quantify). D- and L-lactate accounted for 64% anion gap increase in diarrheic calves. Fecal D- and L-lactate concentrations were also significantly higher in diarrheic calves (9.4 +/- 3.0 and 11.9 +/- 2.7 mmol/L) than healthy calves (1.1 +/- 0.1 and 1.6 +/- 0.1 mmol/L). The elevated concentrations of serum and fecal D-lactate suggest gut bacterial fermentation contributes to the development of acidosis in diarrhea.

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The effect of column length on C02-crude oil minimum mis-cibility pressure (MMP) has been investigated in linear porous media. Sandpacks were placed in a vertical position and crude oil was displaced from them by C02 at pressures ranging from 5.17 MPa to 12.41 MPa. A Co2 crude oil miscibility pressure was established in each of the sandpacks. A 34 0 API gravity (at 25.6 OC) Foster Crude Oil, and three 1.59 cm diameter sandpacks, 0.5 m, 1.5 m and 6 m long respec-tively, were used for the study. The investigation was conducted at 48.8 OC.The results of the tests showed that the C02-crude oil MMP was independent of the length of the sandpack in the range Of lengths used. The crude oil was miscibly displaced from each of the three sandpacks at 10.34 MPa. The hydrocarbon pore volume of CO, required to achieve similar oil recoveries (per cent oil-in-place from the sandpacks was higher for the shorter sandpack and lower for the longer sandpacks at corresponding flooding pressures. While the breakthrough oil recoveries (per cent oil-in-place from shorter columns were less than that from the longer ones. More oil was recovered from shorter than from longer columns after breakthrough at similar flooding Pressures-Introduction A major factor to be considered when planning C02 miscible flooding is the C02-crude oil miscibility pressure. Earlier reports(],2) have demonstrated that displacing crude oil by C02 will result in high oil recovery if carried out above the miscible pressure. The C02-crude oil MMP is usually determined (3-5) by performing C02-crude oil displacement tests at different pres-sures in the laboratory.Menzie and Nielsen(2) and Holm and Josendale(3) have studied the mechanism by which C02 generates miscibility with crude oil. They showed that the process is due to the ability Of C02 to extract hydrocarbons (C5 through C30) from crude oils. The study also demonstrated that, for a given crude oil, *Present address: Department of Chemical Engineering, Obafemi Awolowo University, ile-Ife, Nigeria. Keywords: C02-crude oil, Column length, Vertical sandpacks, Oil recovery, Flooding pressure, Foster crude oil. more hyd . rocarbons are extracted/vapourized as the flooding pressure is increased. The factors that affect C02-crude oil miscibility pressure have been described in the literature as tem-perature, crude oil composition, and the purity of carbon dioxide(4).Holm and Josendal(3) related the length of the C02-crude oil transition zone to the flooding pressure. Low flooding pressures (near the miscible pressure) are less efficient and will produce long transition zones while high flooding pressures (above the miscible pressure) are more efficient and win result in short transition zones. Adamson and Flock (6) reported that the length of the C02-crude oil transition zone (as in other miscible displace-ment processes) depends on the stability of the transition zone.The transition zone is stable if it is devoid of viscous fingers and if there is a gradual change in fluid properties from that of the in-place reservoi...