High-frequency titrations

J)Other analytical methods which include, among many, a thermometric method (104), a high frequency titration (105), and a colored indicator method (106). 

In a few instances where precipitation prevents conductometry at electrodes in direct contact with the analyte solution, use has been made of high-frequency titration, e.g., with the metal plates outside a measuring capacity cell (see pp. 19 21 and 25) examples are the titration of organic bases with perchloric acid in glacial acetic acid105 and of strong or weak acids with sodium methoxide in DMF106. 

Electrodeposition Potentiometric Titrations Conductometric Titrations High-Frequency Titrations... 

Iron in the concentration range of the order of 3.5 x 10 4 to 7 x 10-4M can be determined by high-frequency titration in the presence of other metal ions in Fe3+/Ti4+ = 1 and Fe3+/Zr4+ = 1. Total concentration of the two cations can be determined by high-frequency titration with cupferron, followed by a redetermination after masking the interfering ions. 

The acid/base behavior of aromatic nitro compds in DMF, Me2CO, MeCOEt, and a mixt of solvents were studied using high frequency titration (Ref 42), Pr2CO/EtOH, MeEtCO/ MeOH and MeEtCO/EtOH are reported as suitable solvents for the potentiometric titration of TNT (Ref 43). Low concns of TNT in air were detected in their negatively charged state via electron transfer from ionized SF6. The charged... 

Aksenenko, A.P. Kreshkov Z.V, Tatamikova, High-Frequency Titration of Aromatic Nitro Compounds as Acids in Anhydrous Solvents , ZhAnalChim 26 (10), 2028-32 (1970)... 

The end result is that high-frequency titrations give a variety of responses, including the usual V-shaped curves, nonlinear intersecting curves, and inverted V-shaped curves. The shape of a curve may vary with frequency, or at a given frequency a change in dielectric constant or salt content can change the response. 

Oscillators. The parallel-tuned oscillator circuit is the most commonly used in high-frequency titration work its circuit is shown in Figure 5.13. The resonance frequency,/i, of an oscillator is given by... 

Figure 5.12. Physical and equivalent circuit of high-frequency titration cell. A High-frequency cell solution, glass cell, and metal electrode arrangement. B ... 

Figure 5.13. Parallel-tuned oscillator circuit for high-frequency titrations with cell addition in dashed-line sectiori). 

Figure 5.15 shows a comparison of a low-frequency acid-base titration at two different ionic strengths with high-frequency titrations conducted at 3 and 10 MHz. In each case, 50 milliequivalents of HCl is titrated with 0.01 N NaOH. Obviously 10 MHz is the best frequency to use, but because of the curvature several additional titration points need to be taken to increase the precision of the endpoint determination. The M-shaped curve resulting at 3 MHz could lead to misinterpretation and an incorrect endpoint. 

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