Potassium hydrogenphthalate

In this connection it must be pointed out that standard samples which have been analysed by a number of skilled analysts are commercially available. These include certain primary standards (sodium oxalate, potassium hydrogenphthalate, arsenic(III) oxide, and benzoic acid) and ores, ceramic materials, irons, steels, steel-making alloys, and non-ferrous alloys. 

Calculation of molar concentration. This is similar to that described in Section 10.25. The R.M.M. of potassium hydrogenphthalate is 204.22. The variation in the results should not exceed 0.1 0.2 per cent. 

Benzoic acid is sparingly soluble in water (which is a disadvantage) and must therefore be dissolved in 95 per cent ethanol. The mode of use is similar to that already described for potassium hydrogenphthalate (Section 10.27, Procedure B). For a 0.1 M solution, of, say, sodium hydroxide, weigh out accurately 0.4 g portions of the acid into a 250 mL conical flask, add 10- 20 mL of ethanol, shake until dissolved, and then titrate the solution with the strong alkali using phenolphthalein as indicator. A blank test should be made with the same volume of ethanol and the indicator deduct, if necessary, the volume of the alkali solution consumed in the blank test. 

Sodium hydroxide. Prepare a solution of approximately 0.5M sodium hydroxide in methylcellosolve. This should be standardised by titration with potassium hydrogenphthalate using the mixed indicator given below. 

Thermogravimetry is a valuable technique for the assessment of the purity of materials. Analytical reagents, especially those used in titrimetric analysis as primary standards, e.g. sodium carbonate, sodium tetraborate, and potassium hydrogenphthalate, have been examined. Many primary standards absorb appreciable amounts of water when exposed to moist atmospheres. TG data can show the extent of this absorption and hence the most suitable drying temperature for a given reagent may be determined. 

The IUPAC definition of pH39 is based upon a 0.05M solution of potassium hydrogenphthalate as the reference value pH standard (RVS). In addition, six further primary standard solutions are also defined which between them cover a range of pH values lying between 3.5 and 10.3 at room temperature, and these are further supplemented by a number of operational standard solutions which extend the pH range covered to 1.5-12.6 at room temperature. The composition of the RVS solution, of three of the primary standard solutions and of two of the operational standard solutions is detailed below, and their pH values at various temperatures are given in Table 15.4. It should be noted that the concentrations are expressed on a molal basis, i.e. moles of solute per kilogram of solution. 

The British standard (BS 1647 1984, Parts 1 and 2) is also based upon potassium hydrogenphthalate and a number of reference solutions of a range of substances, and leads to results which are very similar to the figures given in Table 15.4. When applied to dilute solutions ( < 0.1 M) at pH between 2 and... 

R FS. 0.05m Potassium hydrogenphthalate. Dissolve 10.21 g of the solid (dried below 130 °C) in water and dilute to 1 kg. The pH is not affected by atmospheric carbon dioxide the buffer capacity is rather low. The solution should be replaced after 5-6 weeks, or earlier if mould-growth is apparent. 

Prepare the buffer solutions for calibration of the pH meter if these are not already available the potassium hydrogenphthalate buffer (pH 4), and the sodium tetraborate buffer (pH 9.2) are the most commonly used for calibration purposes. 

Examples of primary standards include sodium carbonate (NajCOj), oxalic acid (H2C20. 2H20) and potassium hydrogenphthalate. 

Sodium hydroxide is not a primary standard - it has a relatively low GFM and readily absorbs moisture, making it unstable as a solid. The solution also absorbs carbon dioxide and so its concentration is not constant. The accurate concentration of a solution of sodium hydroxide can be determined by titrating it with a solution of a primary standard such as potassium hydrogenphthalate. 

The amino resin (10-20 mg) was treated with 0.01 M HCIO4 in gladal AcOH (5mL) and shaken for 100 h. Excess HQO4 was back titrated with 7 x 10 M potassium hydrogenphthalate in glacial AcOH using crystal violet as indicator. 

Fig. 3-28. Separation of various inorganic anions on a Wescan 269-001 silica-based anion exchanger. — Eluent 0.004 mol/L potassium hydrogenphthalate flow rate 1.5 mL/min detection direct conductivity injection volume no specification solute concentrations 10 ppm each (taken from [34]).

Fig. 3-62. Separation of inorganic anions using potassium hydrogenphthalate as the eluent. — Separator column Waters IC-PAK Anion eluent 0.001 mol/L KHP, pH 7.0 flow rate 2 mlVmin detection direct conductivity injection volume 10 pL solute concentrations 100 ppm each.

Potassium hydrogenphthalate is suited for the analysis of iodide, thiocyanate, and thiosulfate in combination with direct conductivity detection. When silica-based exchangers are used, some methanol or 2-propanol is added to the eluent to lessen adsorption effects. Fig. 3-77 shows such a separation, the characteristic of which is the elution of monovalent iodide prior to the divalent sulfate. Noticeable is the relatively long time... 

Figure 2.36 Example of photoelectrochemical conditioning for H-termination of crystalline Si, n-Si(113). (a) Photoanodization in potassium hydrogenphthalate buffer for growth of thicker oxides, the potential was increased stepwise when the anodic current reached lOOpAcm initial potential, -0.4V end potential, 9.5 V. (b) Oxide removal in two...

Potassium hydrogenphthalate Potassium hydrogenbiiodate Silver nitrate Sodium oxalate Arsenic(lll) oxide Potassium dichromate Ammonium hexanitrocerate(IV) Potassium iodate Potassium bromide Calcium carbonate Zinc oxide Ni, Zn, Cu metals Anhydrous disodium EDTA... 

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