Degree of ionisation

K is the equilibrium constant at a particular temperature and is usually known as the ionisation constant or dissociation constant. If 1 mole of the electrolyte is dissolved in Vlitres of solution (V = l/c, where c is the concentration in moles per litre), and if a is the degree of ionisation at equilibrium, then the amount of un-ionised electrolyte will be (1 — a) moles, and the amount of each of the ions will be a moles. The concentration of un-ionised acetic acid will therefore be (1 — a)/ V, and the concentration of each of the ions cl/V. Substituting in the equilibrium equation, we obtain the expression ... 

The addition of a tenth of a mole of sodium acetate to a 0.1M solution of acetic acid has decreased the degree of ionisation from 1.32 to 0.018 per cent, and the hydrogen ion concentration from 0.00132 to 0.000018 mol L-1. 

Generally it is only the non-dissociated or unionised drug that is lipid-soluble and a drug s degree of ionisation depends on its dissociation constant (pA) and the pH of the environment in which it finds itself. For an acidic drug this is represented by the Henderson Hasselbalch equation as... 

Table 8.62 shows the main characteristics of ICP-MS, which is widely used in routine analytical applications. The ICP ion source has several unique advantages the samples are introduced at atmospheric pressure the degree of ionisation is relatively uniform for all elements and singly charged ions are the principal ion product. Theoretically, 54 elements can be ionised in an ICP with an efficiency of 90 % or more. Even some elements that do not show ionic emission lines should be ionised with reasonable efficiency (namely, As, 52 % and P, 33%) [381]. This is one of the advantages of ICP-MS over ICP-AES. Other features of ICP-MS that make it more attractive than ICP-AES are much lower detection limits ability to provide isotopic ratio information and to offer isotope dilution capabilities for quantitative analysis and clean and simple spectra. The... 

Since the degree of ionisation in the initiator solution, although generally not known precisely, is certainly very small, we have a simple explanation of the notoriously low... 

It has been shown that the catalytic action of acids is proportional to their strength, of which their degree of ionisation is an expression. Conversely, the strength of an acid can be determined by measuring the rate of hydrolysis of an ester (usually methyl acetate) in aqueous solution in the presence of the acid concerned. 

The hydrogen ion concentration has an effect on enzyme activity because many of the amino acid groups in an enzyme bear ionisable groups. Changes in pH will alter the degree of ionisation of some of these groups and so affect the ionisation of the enzyme molecule as a whole, modifying enzyme activity in at least three ways ... 

From this relationship for acetic acid it is possible to determine the degree of ionisation of acetic acid at a given pH. 

Thus the mobility of an ion can be influenced by its pFa value the more it is ionised the greater its mobility and its molecular shape in solution. Since its degree of ionisation may have a bearing on its shape in solution, it can be seen that the behaviour of analytes in solution has the potential to be complex. For many drugs... 

The ability of a drug to penetrate cell membranes is determined by its chemical structure and its physicochemical properties, in particular the degree of ionisation, protein binding and lipid affinity. Lipid-soluble drugs diffuse easily across membranes, whereas water-soluble ones pass through at slower rates. 

The mobile phase is an aqueous solution containing electrolytes and, if necessary, a small content of methanol used to dissolve samples that have a low degree of ionisation. In this medium, the solutes and the functional groups of the stationary phase are ionised. The elution mechanism is based on the displacement of ionic equilibria. 

Stable sols of arsenic trisulphide in concentrated acids, including sulphuric, phosphoric, acetic and trichloracetic acids, have been prepared.7 In such sols coagulation occurs if a certain degree of ionisation of the acid is reached. 

Studies of isoelectronic sequences of atomic systems (that is, a number of elements with gradually increasing atomic number and degree of ionisation such that they all possess the same number of electrons) are, as mentioned above, very fruitful in theoretical, semiempirical and experimental investigations of atomic spectra. They reveal important regularities and pecularities in the behaviour and physical characteristics of many-electron atoms and ions, help to identify and classify their energy levels within an optimal coupling scheme, find values of semiempirical parameters, etc. 

Polyacrylic acid was chosen as the stabilising moiety because there is a substantial body of literature on its solution properties and because Napper (12) has demonstrated a correlation between critical flocculation temperature and 0-temperature for particles stabilised by copolymers of unionised PAA. Also, since PAA is a weak acid the degree of ionisation can be varied by titration with base. 

Typical potentiometrie titration data for the latices and also for the PAA solutions are shown in Figure 3 in the form of a plot of effective pK (15) against degree of ionisation (a1). 

States of Ionisation The values of successive I.E.—increase with the degree of ionisation, i.e. 

THE USE OF THE HENDERSON-HASSELBALCH EQUATION TO QUANTIFY THE DEGREE OF IONISATION OF A DRUG SPECIES... 

Some synthetic polyelectrolytes with a high degree of ionisation in dilute aqueous solutions... 

In aqueous solutions of poly(acrylic acid), for instance, the carboxyl groups of the polymer can be neutralised by the hydroxide ions of sodium hydroxide. The fraction of the carboxyl groups neutralised is called the degree of ionisation a . For = 1, the polymer is called sodium polyacrylate. 

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