Volumetric loops

Most of the 100 mL of seawater in the sample syringe (about 2/3) is used to flush the sample volumetric loop, before valve 1 is turned. The purge gas backflushes the water out of the loop and via valve 2 to the purge chamber. 

Automated controls for flocciJating reagents can use a feedforward mode based on feed turbidity and feed volumetric rate, or a feed-back mode incorporating a streaming current detector on the flocculated feed. Attempts to control coagulant addition on the basis of overflow turbidity generally have been less successful. Control for pH has been accomplished by feed-forward modes on the feed pH and by feed-back modes on the basis of clarifier feedwell or external reaction tank pH. Control loops based on measurement of feedwell pH are useful for control in apphcations in which flocculated sohds are internaUy recirculated within the clarifier feedwell. 

In Figure 4.1, the CSTR is connected to a recycle loop and measurement cells. If the cells and recycle loop have a volume V and the pump has a volumetric pumping speed of Vp then the characteristic residence time is With our various... 

The consequences of this type of activated physical adsorption is not only that the quantity adsorbed can lie off the isotherm but also that the measured quantity of adsorption is far less than the equilibrium value. No experiments have been conducted to illustrate whether or not the quantity adsorbed lies within the hysteresis loop. The occasional failure of the vacuum volumetric method to agree with the dynamic method, which is not subject to any pressure overshoot, may in part be attributed to this phenomenon. 

Analysis. The solution in each bubbler was transferred to a 25 mL volumetric flask and diluted to volume with the collection medium (10 3 M Na2C03). In the case of samples collected from diluted diesel exhaust, an excess (3 mL) of this solution was flushed through a 100 yL sample loop of Dionex Model 14 ion chromatograph. The sample was analyzed on the anion system with instrumental conditions presented in Table I. 

In 1990, Bushey and Jorgenson developed the first automated system that coupled HPLC with CZE (19). This orthogonal separation technique used differences in hydrophobicity in the first dimension and molecular charge in the second dimension for the analysis of peptide mixtures. The LC separation employed a gradient at 20 (xL/min volumetric flow rate, with a column of 1.0 mm ID. The effluent from the chromatographic column filled a 10 pU loop on a computer-controlled, six-port micro valve. At fixed intervals, the loop material was flushed over the anode end of the CZE capillary, allowing electrokinetic injections to be made into the second dimension from the first. 

K.H. Choi, W.K. Lee, Circulation liquid velocity, gas hold-up, volumetric oxygen transfer coefficient in external-loop airlift reactors, J. Chem. Technol. Biotechnol. 56 (1993) 51-58. 

The free enzymes FIA system permitted analysis in a linear range of 0.05-1.0 g of ethanol/L, a sampling frequency of 15 analyses/h, and a relative SD of 3.5%. The total volumetric flow was 5 mL/min, and the six-channel injection valve permitted the introduction of 0.185 mL (loop volume) of enzymes-reagents solution per analysis (4). Ethanol solutions of different concentrations were used to determine the linear working range and for the calibration curve construction (Fig. 4), presenting a linear relation up to 1 g of ethanol/L with a correlation factor of 0.9899 for six samples. 

For laboratory-scale modification, distinction has to be made between static and dynamic adsorption procedures. In a static procedure, the substrate is contacted with a known volume of gas at a well-defined pressure. The modifying gas may be stationary or circulating in a closed loop. Modification in a static gas adsorption apparatus allows the careful control of all reaction parameters. Temperature and pressure can be controlled and easily measured. Adsorption kinetics may be determined by following the pressure as a function of the reaction time. Figure 8.13 displays a volumetric adsorption apparatus, in which mercury is used, as a means to change the internal volume and for pressure measurement. 

Pycnometer (approximately 70 mL) with wire loop for hanging in bath or Cassia flask one or two 200-mL volumetric flasks 100-mL pipette, and 50-mL pipette if a Cassia flask is used pipetting bulb 250-mL Erlenmeyer flask one 250- and one 100-mL beaker large weighing bottle short-stem funnel spatula filter paper and gum-rubber tube (1 to 2 ft long) if an Ostwald-Sprengel pycnometer is used. 

Similar effects have been found in pressure composition isotherms of LaNi5Hx measured volumetrically [11]. Figure 4 shows variations of the absorption pressure with time to execute an entire measurement loop. As clearly visible, even after a measurement time of one week per cycle, changes in the plateau pressures are observable. 

The electrolytes and acid-base balance should be restored in careful coordination with the renal function. In hyponatraemia, either the fluid intake should be reduced to 700-1,000 ml/day, or a combination of a hypertonic salt solution (3%) and a loop diuretic should be administered intravenously, (s. p. 308) Likewise, an attempt can be made using a combination of diuretics and urea diuresis. Generally, sodium and water intake should be restricted. It is imperative to achieve an even volumetric balance, possibly supported by the cautious intake of fluid. 

FIGURE 5.11 Recorded peaks for different sample injected volumes. X — sample volumetric fraction S — injection instant. The recording tracings correspond to loop-based injections of 59,108,206,403 and 795 pL into a single line flow injection system. Adapted from Anal. Chim. Acta 99 (1978) 37, ]. Ruzicka, E.H. Hansen, Flow injection analysis. Part X. Theory, techniques and trends, with permission from Elsevier (Ref. [80]). 

As the jet travels away from the impeller, it slows down because of the increased area for flow and because more liquid is entrained. Along the centerline of the impeller, the velocity drops more or less linearly with radial distance, and the product 7 r is nearly constant, as was shown by other studies. The total volumetric flow increases with radius to about l.2qg because of further entrainment and then drops near the vessel wall because the flow has started to divide into the upward and downward circulation loops. The maximum flow of 1.2 compared to the radial discharge velocity of 0.6 2 indicates a total flow twice the direct impeller discharge, in agreement with the factor of 2.1 calculated using Eq. (9.9). 

The accuracy of the liquid chromatographic analysis of the generated solutions is limited by the uncertainties involved with the calibration of the sample loop, with the preparation of standard acetonitrile solutions of the PAHs, and with the volumetric measurement of the amount of saturated solution sampled for a given analysis. The random errors associated with each of these processes have been estimated to be less than 1.2%, 0.1%, and 1.0%, respectively. A detailed explanation of how each of these estimates was made is presented elsewhere (39). Quadratic addition of these random errors yields a minimum uncertainty of 1.6% for the quantitative analysis of the generated saturated solutions and hence a potential accuracy of greater than 98% for the method. 

To illustrate density measurement by capacitive methods, the performance of the ANL capacitive mass flowmeter is described. Instrument evaluation tests were conducted at the ANL Solid/Liquid Test Facility (SLTF), shown schematically in Fig. 6.19. The SLTF was designed as a specialized instrument-testing and calibration-loop facility for various liquid and liquid/solid media. The facility can provide volumetric flow rates that range from 0 to 10 L/s and flow speeds up to 6 m/s in 2-in. Schedule 40 pipe. It is equipped with an acoustic cross-correlation flowmeter, a PNA system to... 

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