Filtration, potentiometric

Study of a system of sodium carbonate and Rm2 sodium silicate from a concentrated solution with 45% dry extract (2Si02, Na20). (We shall see in the section on silicates that the nature of the original silicate plays an important role.) The experimental study of the postreaction species obtained was carried out by filtration, potentiometric titration by specific electrode, and complexo-metric titration by EDTA. At equilibrium, the calcium is found in three different forms whose relative proportions vary considerably with the silicate/carbonate proportion ... 

Add a known volume ofo oaM.AgNOj solution (in excess) and boil the solution until the silver chloride has coagulated. Filter through a conical 5 cm. funnel, ensuring that the filter-paper does not protrude above the r m of the funnel. Wash the silver chloride and the filter-paper several times with a fine jet of distilled water. To the united filtrate and washings add i ml. of saturated ferric alum solution. The solution should be almost colourless if it is more than faintly coloured, add a few drops of concentrated nitric acid. Then titrate with 0 02M-ammonium thiocyanate solution until the permanent colour of ferric thiocyanate is just perceptible. (Alternatively the chloride may be determined potentiometrically.)... 

In electro-gravimetric analysis the element to be determined is deposited electroly tically upon a suitable electrode. Filtration is not required, and provided the experimental conditions are carefully controlled, the co-deposition of two metals can often be avoided. Although this procedure has to a large extent been superseded by potentiometric methods based upon the use of ion-selective electrodes (see Chapter 15), the method, when applicable has many advantages. The theory of the process is briefly discussed below in order to understand how and when it may be applied for a more detailed treatment see Refs 1-9. 

Pyrolusite. Dissolve 1.5-2 g, accurately weighed, pyrolusite in a mixture of 25 mL of 1 1 hydrochloric acid and 6 mL concentrated sulphuric add, and dilute to 250 mL. Filtration is unnecessary. Titrate an aliquot part containing 80-100 mg manganese add 200 mL freshly prepared, saturated sodium pyrophosphate solution, adjust the pH to a value between 6 and 7, and perform the potentiometric titration as described above. 

Anal. Calcd. for recrystallized [PtCl2(NH3)2] Cl, 23.6 Pt, 65.0. Found Cl, 23.5 Pt, 65.0. Cl is analyzed potentiometrically after decomposition of a sample with hydrazine in aqueous alkaline medium followed by filtration of metallic Pt and acidification of the filtrate with HN03. The Pt is analyzed gravimetrically after decomposition of a sample by heating with Na2C03. 

G.B. Sigal, D.G. Hafeman, J.W. Parce and H.M. Mcconnell, Electrical-properties of phospholipid-bilayer membranes measured with a light addressable potentiometric sensor, ACS Symp. Ser., 403 (1989) 46-64. J.D. Olson, P.R. Panfili, R. Armenta, M.B. Femmel, H. Merrick, J. Gumperz, M. Goltz and R.F. Zuk, A silicon sensor-based filtration immunoassay using biotin-mediated capture, J. Immunol. Methods, 134(1) (1990) 71-79. 

NaCl solution. In one set of experiments, the slurry was titrated with 0.1 normal NaOH solution in one cm increments to a pH of about 10. The samples of this set are referred to as the "slurry" samples (titration of the calcined zeolite - NaCl solution slurry). In another set of experiments, the calcined zeolite - NaCl solution slurry was filtered, the filter cake washed with about 100 cnP distilled water, and the combined filtrates were titrated with 0.1 N NaOH solution, again to a pH of about 10. The samples of this latter set are referred to as the "filtrate" samples (the zeolite being removed by filtration prior to titration of the filtrate). In addition to the manual titrations, automated potentiometric titration curves were obtained with a Metrohm E636 Titroprocessor, which has an estimated pH measurement accuracy of 0.001 pH unit and an estimated volumetric addition accuracy of 0.001 cm ... 

Potentiometric titration curves obtained with the filtrates following NaCl treatment of these last samples (treated at 1000°C) are shown in Figure 6. Little acidity is observed. 

Figure 6. Potentiometric titration curves for 1000 C calcined NH - and H O -ZSM-5 filtrate samples.

Hydrous sodium titanate was prepared by the method of Dosch and Stephens (1). Titanium isopropoxide was slowly added to a 15 wt% solution of sodium hydroxide in methanol. The resulting solution was hydrolyzed by addition to 10 vol% water in acetone. The hydrolysis product is an amorphous hydrous oxide with a Na Ti ratio of 0.5 which contains, after vacuum drying at room temperature, approximately 13.5 wt% water and 2.5 wt% residual alcohol. The ion-exchange characteristics of the sodium titanate and the hydrolysis behavior of the nickel nitrate solutions were characterized using a combination of potentiometric titrations, inductively coupled plasma atomic emission (ICP) analysis of filtrates, and surface charge measurements obtained using a Matec electrosonic amplitude device. 

Part 4 of ISO 787 specifies the method of determination and Part 3 specifies how the extract should be prepared. The material for testing is extracted in boiling water for 5 minutes and filtered to obtain a clear filtrate. An aliquot of filtered extract is titrated either with hydrochloric acid or sodium or potassium hydroxide solution in the presence of an indicator or evaluated by potentiometric determination. 

Methods of functional group analysis that are based on pKa values of the functional groups (all potentiometric methods) can only yield operationally defined estimates of the concentration of a particular class of acidic functional groups. For this reason, an increased reliance on spectroscopic methods of functional group analysis is recommended. Only total acidity, as determined by the barium hydroxide method, appears to be a potentially accurate potentiometric method of analysis, if some type of ultrafiltration technique is used whenever normal filtration fails to remove all color from reaction mixtures. 

In many cases the application of a potentiometric titration to the analysis of a food sample is straight-forward. In determining the titratable acid in mustard the sample is taken up in distilled water, stirred for a set time period and then titrated directly with a standard NaOH solution. In other cases, such as solid or semi-solid foods, the sample must be homogenized in the uptake solution and treated to ensure solution of the analyte. It is necessary in some situations to separate the liquid sample portion by filtration, centrifuging, etc., prior to titration with the standard solution involved. 

O. Fatibello-Filho, J.A. Nobrega, Flow injection potentiometric determination of saccharin in dietary products with relocation of filtration unit, Talanta 41 (1994) 731. 

Both the Sephadex gel (C-50-120) received from the Sigma Chemical Company and the cross-linked PMA (Amberlite IRC-50) received from the Rohm and Haas Company were first treated with 1M HC1 to convert them completely to their acid form. After complete removal of excess acid was assured by exhaustive washing with deionized water, the water was withdrawn from the Sephadex by filtration. The moist gel was then stored in a sealed polyethylene bottle. Reproducible sampling for an experiment from this source was demonstrated by the high precision obtained from capacity measurements of samples taken concurrently with those used in the potentiometric measurements program. 

Analytical estimation of Cl in soil suspensions can be performed (following filtration or centrifugation) by potentiometric titration, automatic colorimetric analysis (automated ferricyanide method) and ion chromatography. Choice of... 

A rapid immunotechnique combining separation of reactants by filtration through a porous membrane and potentiometric detection of the bound enzyme label by a... 

Fill., filtration Evap., evaporation FI. det., fluorimetric detection SLE, solid-liquid extraction SEC, size-exclusion chromatography MD, microwave digestion LLE, liquid-liquid extraction Imm., immunoassay Phot, det., photometric detection FI. det., fluorimetric detection BOD, biological oxygen demand DOM, dissolved oxygen measurement SPE, solid-phase extraction Centr., centrifugation Mix., vortex mixing PCBs, polychlorinated biphenyls Pot. det., potentiometric detection TCP, 3,5,6-trichloro-2-pyridinol. 

The intensity of scattered light was measured by Brice-Phoenix OM-2000 photometer at 436 nm as a function of scattering angle (45° -135°). The solutions were filtrated by Millipore membrane filter. A stock solution of 0.4% PVP made in NaDS solution was diluted at constant chemical potential of the solvent. The composition of the solvent for dilution was determined from potentiometric and equilibrium dialysis measurements as well. Refractive index increments were determined by Brice-Phoenix differential refractometer. 

The test in its modified form is performed with pyridine hydrochloride which converts the liberated amino groups on polymer again into the hydrochloride. After extensive washings the salt is released from its anchor functions by deprotonation with triethyl-amine, followed by repeated rinses of the polymer. The filtrates of this particular deprotonation and subsequent washings are collected and the chloride concentration therein is measured by potentiometric titration with silver nitrate. 

The wet MBP cake after filtration generally contains about 60-90 % water by weight, and this must be removed to an acceptable level. Thus, the drying step is one of the most critical steps in MBP manufacturing and should be closely monitored. Water level in the cake can be monitored by water activity of the outlet air and further confirmed by more sensitive moisture measurements such as potentiometric titration. 

C. Titration with NaTPB. The solution must be at least 0.1 M in hydrogen ion. Potentiometric titration is preferred, but two-phase titration should be satisfactory. It may be more effective to add a measured excess of NaTPB, filter or centrifuge (or run off the chloroform layer) and determine the excess by precipitation with potassium, filtration and weighing. 

Sulphate concentrations may also be determined accurately by potentiometric back-titration of excess Ba + with a mercury electrode following the precipitation of BaS04 Mucci, 1991). The seawater sample is freed from most seasalt cations with an ion-exchange-column. Then the eluate is reacted with an excess of barium, and after filtration of precipitated BaS04, the solution is titrated potentiometrically with an EGTA solution (see also Section 11.2) to the endpoint. The method applies over a wide range of salinities and sulphate concentrations in 1 mL or less of seawater and marine pore water samples, however, it is somewhat less precise (c.v. of about 0.6 %) than the simple gravimetric procedure described. 

One gram of a meat sample is sonicated in 100 cm water. The obtained dispersion is filtered. Twenty-five cubic centimeters of the filtrate is mixed in the 1 1 volume ratio with 0.5 M nitric acid used as an ISAB solution. The same ratio of the ISAB is added to the calibrating standards. The usual direct potentiometric method gives the chloride ion concentration of the extracting solution. The sample concentration is given as micrograms per gram of meat. 

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