Ionic product determination

Such electrodes make use of an enzyme to convert the substance to be determined into an ionic product which can itself be detected by a known ion-selective electrode. A typical example is the urea electrode, in which the enzyme urease is employed to hydrolyse urea ... 

The heat of formation CH5 + is taken as 229 =fc 3 kcal./mole as determined recently in these laboratories (9). In all these energetic considerations we assume that all the energy of the reaction is concentrated in the ionic product species. Thus, the energies written are upper limits to the energies the ionic species actually contain. 

As the pure solvent is only slightly ionized, both the activity coefficients and the concentration of the non-ionized solvent molecule may be regarded as unity, and one prefers to use Kw = [H30+][0H ], the so-called ionic product of water. It was determined for the first time by Kohlrausch and Heydweiller at 18° C from the conductivity, k = 0.0384 10"6 (cf., Ch. 2), which is given by... 

The ion product of water depends on the ionic strength of the system and on its temperature. At 25 °C and in low ionic strength solution, log = -13.99, whereas in 3 M NaC104 (the ionic medium used by Schindler et al., 1963 for solubility product determination), log = -14.22 + 0.1 the value chosen must correspond to the ionic strength of the system involved. 

In 1972, Miller made a detailed analysis of the data on the influence of electron acceptor additives on the yield of ionic products during radiolysis of organic matrices and showed this to agree quantitatively with the electron tunneling mechanism of the formation and annihilation of these particles [7], In particular, the annihilation of et) in MTHF glass containing naphthalene (Nh) as the additive was found to be accompanied by simultaneous formation of the Nh anion radical (via the reaction etj. + Nh - Nh ). The kinetic curves for this reaction at 77 and 87 K coincided, which ruled out the possibility of the reaction rate being determined by thermal diffusion. 

The structures and isomerization of C4Hg+ ions in connection with the problem of ethylene clusters has been the subject of many studies. Doepker and Ausloos192 studied the photolysis of cyclobutane, its deuterated isotopomer and mixtures thereof, and in their detailed product analysis they found cA-2-butene, trans-2-butene and 1-butene as major ionic products in the approximate ratio of 1 1 2. Lias and Ausloos193 determined... 

The fact that the ionic product of D20 is several times smaller than the ionic product of ordinary water was one of the earliest firm results in deuterium chemistry (Abel et al., 1935 Wynne-Jones, 1936 Schwarzenbach et al., 1936). Three recent electrometric determinations (Gold and Lowe, 1963,1967 Covington et al., 1966 Pentz and Thornton, 1967) agree that the difference in pAw values is in the range 0-860-0-870 at 25°C a lower difference (0-809) was reported by Salomaa et at. (1964). 

It has been demonstrated that it is possible to determine reliable relative basicities by employing the kinetic method. By this method, a proton bonded dimer is caused to dissociate, and the difference in basicity of the constituent monomers is derived from the ratio of ionic products of the two competing dissociation channels [9] ... 

Determination of Ionic Product Conductance Method.—Since it contains a certain proportion of hydrogen and hydroxyl ions, even perfectly pure water may be expected to have a definite conductance the purest water hitherto reported was obtained by Kohlrausch and Heyd-weiller after forty-eight distillations under reduced pressure. The specific conductance of this water was found to be 0.043 X 10 ohm cm. at 18 , but it was believed that this still contained some impurity and the conductance of a 1 cm. cube of perfectly pure water was estimated to be 0.0384 X 10 ohm i cm. at 18 . The equivalent conductances of hydrogen and hydroxyl ions at the very small concentrations existing in pure water may be taken as equal to the accepted values at infinite dilution these are 315.2 and 173.8 ohms cm. respectively, at 18 , and hence the total conductance of 1 equiv. of hydrogen and 1 equiv. of hydroxyl ions, at infinite dilution, should be 489.0 ohms cm. It follows, therefore, that 1 cc. of water contains... 

Conductance measurements have been used to determine the ionic products of the amphiprotic solvents ethyl alcohol, formic acid and acetic acid. 

The most satisfactory method for determining the ionic product of water makes use of cells without liquid junction, similar to those employed for the evaluation of dissociation constants (cf. p. 314). The E.M.F. of the cell... 

The Ionization of Water in Halide Solutions.—The cells employed for the determination of the ionic product of water have also been used to study the extent of dissociation of water in halide solutions. Since Ku, is equal to an aoH and aH aoirlyn yon- is equal to equation... 

Anionic alkyl ether sulfate surfactants are produced by sulfating nonionic alcohol polyalkyloxylates such as the ethoxylated surfactants discussed earlier. The sul-fated products generally contain variable amounts of unconverted alcohols and inorganic salts as reaction by-products. Determination of the ratio of anionic to nonionic components in surfactant mixtures is desired for quality control and performance evaluation. Separation of the ionic sulfate and nonionic alcohol components is achieved by reversed-phase chromatography. The separation of four alkyl ether sulfate surfactants is shown in Table 3. 

In the study of ion-molecule reactions the relative intensities of reactants and ionic product are immediately available and thus the reaction rate is readily determined. With the reaction A+ + M — B+ + S, if M is much larger than A+, the reaction rate is psuedo first order and the equation expressing the concentration of A+ and B+ is as follows ... 

The following three examples show the formation of ionic compounds by the complete transfer of one or more electrons from the metal to the nonmetal. In each case, the total number of electrons lost equals the total number gained. Note that each ion has the electronic configuration of a noble gas. As you inspect each example, notice how the number of electrons lost by the metal and gained by the nonmetal determines the formula of the ionic product. The formula of the product can be predicted from the electronic configurations of the reactants. 

Editors note Using the Authors value for lhe ionic product of formic acid, this corresponds to a pK. value of ca. +4.6, and their figure for tetrazole itself to a pK, of 4.8. Clearly, these values are not directly comparable with those determined in aqueous sulfuric acid (see Section... 

Various methods have been employed for the experimental determination of the ionic product of water. We will mention them here briefly ... 

EMF Method, The ionic product can also be obtained from emf measurements on voltaic ceils. The principle of the method is to prepare an alkaline solution of known hydroxide-ion concentration, and then to determine the hydrogen-ion concentration by dipping into the solution a hydrogen electrode and a reference electrode, then measuring the emf (Chapter 8). Instead of the hydrogen electrode one may, of course, use a glass electrode or any other electrode which responds to the hydrogen-ion concentration. 

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