PH vs. time

If no pH recorder is available, pH readings can be taken from the meter or digital readout and a graph of pH vs. time prepared. Record a pH reading every 10 seconds. 

If no recorder tracing is available, prepare a graph of pH vs. time for each experiment. Prepare and complete a table with the following headings ... 

Figure 3. Predicted Behavior of Solution pH vs. Time for Various Values of. ...

Figure 2. pH vs. time after mixing equal volumes of 10 mH HCl and 20 mM NaHCOs at 26°C. The original oscilloscope tracing is in the left upper comer... 

Figure 7. Extracellular pH vs. time after mixing equal volumes of suspension A (Pco2 — 0) and solution B (pCo2 — 65 torr) at 37°C...

In some clock reactions, however, there is a narrow range of concentrations in which the quality of the mixing becomes critically important. Under these conditions, the time of the sharp transition from initial to final state becomes essentially unpredictable. The prototype system of this type is the chlorite-thiosulfate reaction (Nagypal and Epstein, 1986). Measurements of pH vs. time for five replicate experiments starting from the same initial concentrations are shown in Figure 15.8. For the first several minutes, all the curves are identical. The pH increases smoothly. In three of the curves, we observe a sharp drop in pH at approximately 3, 5, and 9 min in the other two, this decrease occurs at times greater than 20 min. When an acid-base indicator like phenolphthalein is added to the solution, the pH... 

Figure 10.1 Electrode potential (E] and pH vs. time curves measured during the reduction of Mn04 ions in the 200 ml aqueous solution of 0.1 M KMn04 containing 1.0 g CNT at 70°C.

Fig. 31. Bubble wall velocity vs time during cavitational collapse for different values of the parameter X defined as X ss 0.4 c iTl] p./fri/2 (Ph — Pv)i/2). X permits us to account for the viscous and inertia effects of the polymer solution (redrawn according to Ref. [122]) ...

Figure 8. Product composition vs. time for glyceric acid oxidation at pH=10-ll on 5%Pt2%Bi/C.

Figure 4. Rigidity vs. time for a high standard rigidity (250 Bloom) calfskin gelatin at 10° C, pH 6.0, 0.1 sodium chloride...

Figure 16 Reaction rate determination of 1,2/1,4 ketal in LANA reaction (scheme 5). Yield, graphed on the y-axis vs. time on the x-axis, was estimated by RPLC on Zorbax C18. Column 25 cm x 4.6 mm (5 p). The mobile phase was 100 mM KH2P04 (pH 6.5) acetonitrile (45 55) at 1.0 ml/min. The column temperature was 35°C, and detection was at 254 nm.

Figure 1. Absorbance at 400 nm vs. time for the poly(4-pyrrolidi-nopyridine) and 4-pyrrolidinopyridine catalyzed hydrolysis of p-nitrophenylacetate at pH 8.5.

Fig. 16. Slow isotopic exchange at 35.0°C on Re(V) center, (a) Oxygen-17 spectra showing signal growth vs time for [Re02(CN)4]3. (b) Least-squares fit of the data to the modified exponential McKay equation (7). The total complex concentration [Re] = 0.2 m, pH = 6.6, and fi = 1.2 m (KN03). (Adapted with permission from Roodt, A. Leipoldt, J. G. Helm, L. Abou-Hamdan, A. Merbach, A. E. Inorg. Chem. 1995, 34, 560-568. Copyright 1995 American Chemical Society.)...

Figure 3. Long-term corrosion measurement of an electrolytic Sn-Zn alloy containing 26% Zn (by weight) in a 3% NaCI solution, pH = 4.000, with argon bubbling through the solution. Upper diagram corrosion potential vs. time lower diagram CMT and EC measurements vs. time. After 80-100 min, the ratio CMT/BC is close to 4. (Reprinted from Ref. 2, with kind permission from Elsevier Science Ltd., Kidlington, Oxfmd, UK.)...

Fig. 15. Inhibition of the lysis of Micrococcus luteus by lysozyme, kiko (ko = activity in the absence of inhibitor) (A, 0), and optical density increase of an M. luteus suspension at 500 nm, both as a function of polyelectrolyte concentration. Poly(Lys), O Poly(Glu), pH 8.5, I = 0.01, lysozyme 0.55 x 10" M. M. luteus 100 mg liter", +20°C. Inset Recording vs time of the optical density increase of an M. luteus suspension on addition of poly(Lys) at 2.5 X 10" M, at +20°C.

Fig. 1.7 Semilog plot of optical absorbance at 540 nm vs time for hydrolysis of Co(medta)Br at 78.8 °C and pH 2.6. Mixture of isomers (-(-) fast component derived from mixture by subtraction of slow component (o) experimental points for fast isomer...

Two types of amphiphilic quaternary 3-pyridinium ketoximes (253a, b) with different positioning of the hydrophobic alkyl chain have been synthesized and tested as hydrolytic micellar catalysts. A considerable positive deviation from the expected first-order curve was observed in the absorbance vs time plot when p-nitrophenyl diphenyl phosphate (252 R = Ph) and p-nitrophenyl diethyl phosphate... 

An example of anomalous behavior in closely related systems was reported some time ago during an investigation of the cychzation products derived from coumarin semicarbazones (Scheme 6.21). Thus, 78a reacted cleanly with chloro-acetic acid to yield 79a, which cyclized to the expected product 80a upon treatment with sodium acetate. On the other hand, 79b did not cyclize under the same reaction conditions. This was attributed to the absence of the enolizable hydrogen (Ph vs. H). The authors did not comment on the possibility of cyclization of 79b to 80b. The closely related urea analogue 81 did not react with chloroacetic acid thereby... 

Preliminary data have been obtained for 0.01 M solutions at pH 2.0 (added hydrochloric acid) and solutions buffered to pH 5.5 with O.lM acetate buffer. The principal interest, however, was in the C-T system (solutions brought to pH 10.5 with added ethylenediamine) for which most of the photochemical results were obtained. An example of the direct data for the C-T system is shown in Figure 1. Over the period of 120 hours, Dot decreased by about 3%, corresponding to about 6% aquation. The procedure was then to calculate from each measurement an effective D00 value D00 = Dot/(l + K). Plots of (D°°-Dt) and of (Dq-D /K vs. time should then superimpose. This was reasonably the case, as illustrated in Figure 2, for data at two wave lengths. 

The release curve of ketoprofen obtained from the KET-R tablet at pH 1.2 and 50 rev/min is shown in Fig. 1. The release profile was zero order up to 90% drug content. The equation obtained by plotting the percentage released vs. time was y=0.187x-1.997, 0.99. No burst effect was present. 

Fig. 3—Glassy core volume decrease of tablets KET-R vs. time , pH 1.2 pH 6.8.

Figure 7.3. (a) In situ X-ray reflectivity vs. time (measured at the anti-Bragg condition, shown in inset at top) during dissolution of orthoclase feldspar, KAlSi308, (001) cleavage surface at extreme pH values. The removal of successive monolayers (ML) is noted for each set of data, (after [100]) (b) in situ crystal truncation rod diffraction profiles for a freshly cleaved orthoclase (001) surface (circles) and after reaction at pH = 2.0 (1 and 15 ML dissolved) (diamond and square) and pH = 12.9 (2 ML dissolved) (triangle) (after [103]). (Figures provided by P. Fenter.)... 

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