PH buffer solutions

Table 8.14 National Bureau of Standards (U.S.) Reference pH Buffer Solutions 8.105...

Table 8.15 Compositions of Standard pH Buffer Solutions [National Bureau of...

The buffer values for the NBS reference pH buffer solutions are given below ... 

To prepare the standard pH buffer solutions recommended by the National Bureau of Standards (U.S.), the indicated weights of the pure materials in Table 8.15 should be dissolved in water of specific conductivity not greater than 5 micromhos. The tartrate, phthalate, and phosphates can be dried for 2 h at 100°C before use. Potassium tetroxalate and calcium hydroxide need not be dried. Fresh-looking crystals of borax should be used. Before use, excess solid potassium hydrogen tartrate and calcium hydroxide must be removed. Buffer solutions pH 6 or above should be stored in plastic containers and should be protected from carbon doxide with soda-lime traps. The solutions should be replaced within 2 to 3 weeks, or sooner if formation of mold is noticed. A crystal of thymol may be added as a preservative. 

Concentration limits of the diphosphate-ion, admissible to determination of magnesium and cobalt, manganese and cobalt, zinc and cobalt by spectrophotometric method with application of the l-(2-pyridylazo)-resorcinol (PAR) are presented. Exceeding maintenance of the diphosphate-ion higher admissible supposes a preliminary its separation on the anionite in the H+-form. The optimum conditions of cobalt determination and amount of the PAR, necessary for its full fastening are established on foundation of dependence of optical density of the cobalt complex with PAR from concentration Co + and pH (buffer solutions citrate-ammoniac and acetate-ammoniac). 

Figure 11. Absorption spectra of gel-immobilized cresol red after immersion in different pH buffer solutions (3, 4, 5, 6, 7, 8, 9, 10) for 1 min. Films prepared from TEOS MTMOS (2 1) sol.

The wireless pH capsule (Medtronic Inc.) is oblong in shape and contains an antimony pH electrode, a reference electrode at its distal tip, a battery, and a RF transmitter. The whole device is encapsulated in epoxy. The capsule is introduced into the esophagus on a catheter through the nose or mouth and is attached to the lining of the esophagus with a clip. The probe monitors the pH in the esophagus and transmits the information via RF telemetry at a rate of 6 per second (0.17 Hz) to a pager-sized receiver that is worn by the patient on a belt. Prior to implantation, the capsule is calibrated with its receiver in pH buffer solutions of pH 1.07 and pH 7.01 [168],... 

The voltammograms for marmatite electrode in different pH buffer solutions are presented in Fig. 4.22. It can be seen from Fig. 4.22(a) that the first anodic peak occurred at about 200 mV, which may be due to the oxidation of dithiocarbamate to disulphide. The anodic oxidation peaks at higher potential may be attributed to the further oxidation of marmatite to form oxy-sulphur and zinc/iron hydroxide resulting in flotation descending. 

Figure 4.22 Voltammograms for marmatite electrode in different pH buffer solution (a) in 0.1 mol/L Na2S04 media at scanning rate of 50mV/s (b) in 0.1 mol/L KNO3 media at scanning rate of 20 mV/s...

Figure 4.28 The anodic scan section of cyclic voltammetry for pyrrhotite electrode in different pH buffer solution at potential scan of 10 mV/s (Background solution buffer solution plus 0.1 mol/L KNO3, DDTC 10" mol/L)...

To the donor cell, 3 mL of the model drug solution was added, and to the receptor half-cell 3 mL of the solvent was added. Timing of the diffusion of the solute began as soon as both half-cells were filled. At regular intervals (i.e., 15, 30, and 60 minutes) the contents of the receptor cell were moved and replaced with fresh solvent, which in this case was pH buffer solution. To ensure constant temperature of the iimer cell solution, constant-temperature water was pumped through the outer half-cells. 

Figure 2 Equilibrium swelling behavior as a function pH at 22°C in pH buffer solution for PMAA/PNIPAAm IPN samples ( ) containing 70 mol% of PNIPAAm and pure PMAA ( ) samples.

Hart, K. P., Glassley, W. E. McGlinn, P. J. 1992. Solubility control of actinide elements leached from Synroc in pH-buffered solutions. Radiochimica Acta, 58/59, 33-35. 

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