Tetrabutylammonium picrate

Specifications, Analysis, and Toxicity. Dicyandiamide is identified quaHtatively by paper chromatography and quantitatively by ultraviolet spectrometry of the chromatogram. More commonly, total nitrogen analysis is used as a purity control or the dicyandiamide is converted by hydrolysis to guanylurea, which is determined gravimetrically as the nickel salt (50). Methods based on the precipitation of silver dicyandiamide picrate are sometimes used (51). Dicyandiamide can also be titrated with tetrabutylammonium hydroxide ia pyridine solution. Table 4 gives a typical analysis of a commercial sample. Dicyandiamide is essentially nontoxic. It may, however, cause dermatitis. 

The small- r behavior in Fig. 2 is quite surprising from the following point of view. For real 1-1 electrolytes in solvents with e = 10, e.g. tetrabutylammonium picrate in ethylene... 

An example of CO2 enhanced aqueous extraction is shown in Figure 7 for tetrabutylammonium picrate (TBAP). Three common solvents for PTC butyl acetate, methyl isobutyl ketone (MIBK) and methylene chloride were used as the organic phase. 

With the decrease in permittivity, however, complete dissociation becomes difficult. Some part of the dissolved electrolyte remains undissociated and forms ion-pairs. In low-permittivity solvents, most of the ionic species exist as ion-pairs. Ion-pairs contribute neither ionic strength nor electric conductivity to the solution. Thus, we can detect the formation of ion-pairs by the decrease in molar conductivity, A. In Fig. 2.12, the logarithmic values of ion-association constants (log KA) for tetrabutylammonium picrate (Bu4NPic) and potassium chloride (KC1) are plotted against (1 /er) [38]. 

Fig. 1. The variation of the ion-pair association constant with the dielectric constant of the solvent for the electrolyte tetrabutylammonium picrate in nitro-benzene-CCU mixtures (Hirsch and Fuoss, 1960).

Fig. 2 Coexistence curves of the systems tetrabutylammonium picrate + tridecanol and ethylammonium nitrate + octanol. x, is the mole fiaction of the salt.

Monte-Carlo calculations have established the approximate location of the CP, but have provided little insight into the character of these phase transitions. There seems however to be a simple, semi-quantitative way to account for these Coulombic phase separations. For illustration we show in Fig. 4 the equivalent conductance A of the system tetrabutylammonium picrate + tridecanol as a function of the molar concentration C along an isotherm about 6 K above T,. ... 

Fig. 4 Equivalent conductance A (in S cm mol ) of tetrabutylammonium picrate + tridecanol as a function of salt concentration C (in mol dm ) about 6 K above T. The arrow indicates the CP.

In extraction procedures using methylene chloride as organic phase, bromothymol blue has been used as an ion-pairing counterion for amfetamine, and picrate ions for atropine. Tetrabutylammonium ion has been used for the extraction of penicillins into chloroform. 

PMHS, poly(methyl hydrosiloxane) PLF, linear hexafluoro dimethyl carbinol-functionalized polysiloxane PBF, branched hexafluoro dimethyl carbinol-functionalized polysiloxane PMTFPS, poly(methyl-3,3,3,-trifluoropro-pylsiloxane) PCPMS, poly(methyl cyanopropyMoxane) SXCN, poly oxy[bis(3-cyanopropyl-l-yl)silylene] PPE, poly(phenylether) TBTS (molten salt), tetrabutylammonium 4-toluene sulfonate TBP (molten salt), tetra-butylammonium picrate FPOL, fluoropolyol P4V, poly l-[4-(2-hydroxy-l,l,l,3,3,3-hexafluoropropyl-2-yl)phe-nyl]ethylene PEI, poly(ethyleneimine). 

Figure 2.7 shows the concentration dependence of the perpendicular component of the electrical conductivity for two nematic mixtures, A (based on azoxy-compounds) and the Schiff-based mixture B, doped with ionic impurities tetrabutylammonium picrat (TBAP), tetrabutylammonium bromide (TBAB), acceptor impurities tetracyanoethylene (TCE), 2,3-dichloro-5,6-dicyanobenxoquinone (DCDCBQ), tetracyanoquinone-dimethane (TC-QDM), and donor impurity p-phenylenediamine (PDA). Measurements are given for the ohmic part of the current-voltage curves (frequency 1 kHz and cell thickness 100 /xm). The characteristic dependence of a on concentration O oc where c = N/ up/M, predicted for the simple ionization-recombination process discussed, is only observed for ionic impurities. Here the relationship K /Kr can also be determined if we assign a value to the... 

Such an assumption was proposed, namely that a bridge consisting of a 0.1 mol dm tetraethylammonium picrate in acetonitrile suppresses the liquid junction potential between two different nonaqueous electrolytes [6]. The argument in favor of such a salt bridge for nonaqueous electrolytes is the similar electrical mobility of the tetraethylammonium cation and the picrate anion in acetonitrile. This assumption was later expanded to allow for other nonaqueous solvents [28]. Agreement for the electrochemical data was found if the nonaqueous solvents did not have acidic hydrogen atom(s) in the solvent molecule (aprotic solvents) [29], 0.1 mol dm solutions of either tetrabutylammonium picrate or pyridinium trifluorosulftMiate [30] were also used. 

Figure 19. Field dissociation effect as a function of the field strength for solution of tetrabutylammonium picrate (TBAP) in diphenyl ether measured at different frequencies. 3.9xl0 M TBAP, 40 kHz, 1.5 X 10" M TBAP, 40 kHz, 3.9 x 10" M TBAP, 100 kHz. (After Ref. 55.)...

Of the few scattered studies of concentrated solutions of organic salts, Kenausis et were the first to propose an explanation in some detail on the basis of the system (n-C Hn NSCN with -xylene added. By use of the Walden product they showed that approximately one pair of ions was removed from conduction per molecule of xylene added at the two diverse temperatures of 52° and 90° and at concentrations as high as 0.3 mole fraction of xylene. They argue that the nonelectrolyte causes an asymmetry in the Coulomb field about the ions near the nonelectrolyte and induces pairing. From Seward s data< on tetrabutylammonium picrate with butanol added, the amount of ion pair formation per molecule of added nonelectrolyte decreases with increasing dielectric constant of the bulk nonelectrolyte. 

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