Determination of Solubility

When studying a polymer, one should first determine its solubility. This is very characteristic for macromolecules and can serve as an early means of characterization. Important examples are the recognition of crosslinking, the separation and distinguishing between tactic and atactic macromolecules and the identification of copolymers. Moreover, solubility is a prerequisite for most physical measurements. 

When determining the solubility it has to be remembered that macromolecules show extremes of behavior, like swelling and incompatibility (for details see Sect. 1.4.1.2). Although there are many thermodynamic theories for the de- 

Polystyrene Poly(vinyl chloride) Poly(vinyl fluoride) 

Toluene, methylene chloride, cyclohexanone, butyl acetate 

0 Liquid crystalline domains Polarization microscopy. X-ray scattering 

Molecular weight Absolute methods end group analysis, membrane osmometry, vapor pressure osmometry, static light scattering, mass spectrometry, sedimentation measurements 

Relative Methods solution viscosity, melt viscosity, size-exclusion chromatography  

Coil dimensions Light scattering, sedimentatirai measurements, small angle X-ray, solution viscosity 

---

Determination of soluble sodium chloride. By entering the graph in Figure 4-109 with the Ib/bbl of calcium chloride at the correct volume percent of water (by retort) line, the maximum amount of soluble sodium chloride can be found. If the sodium chloride content determined in Step 2 is greater than the maximum soluble sodium chloride determined from Figure 4-108, only the soluble portion should be used for calculating the total soluble salts. 

The general approach illustrated by Example 18.7 is widely used to determine equilibrium constants for solution reactions. The pH meter in particular can be used to determine acid or base equilibrium constants by measuring the pH of solutions containing known concentrations of weak acids or bases. Specific ion electrodes are readily adapted to the determination of solubility product constants. For example, a chloride ion electrode can be used to find [Cl-] in equilibrium with AgCl(s) and a known [Ag+]. From that information, Ksp of AgCl can be calculated. 

R.P.T. Tomkins, G. Hefter and C. Young, The Experimental Determination of Solubilities, John Wiley Sons, Ltd, Chichester (2003). 

May, W.E, Wasik, S.P., Freeman, D.H. (1978b) Determination of solubility behaviour of some polycyclic aromatic hydrocarbons in water. Anal. Chem. 50, 997-1000. 

Methods for the determination of solubility have been thoroughly reviewed [21,22], Solubility is normally highly dependent on temperature, and so the temperature must be recorded for each solubility measurement. Plots of solubility against temperature, as exemplified by Fig. 4 [23,24], are commonly used for characterizing pharmaceutical solids and have been extensively discussed [1,24]. Frequently (especially over a relatively narrow temperature range), a linear relationship may be given either by a van t Hoff plot according to [23]... 

Strickland JDH, Parsons TR (1972) Determination of soluble organic carbon. In Goldberg ED (ed) A guide to marine pollution. Gordon and Breach Science Publishers, New York, pp 70-76... 

There have been many determinations of solubility products for lanthanide fluorides over the years. We shall try to show the range of values presented for a given element, as well as the chemically important variation of solubility with the nature of the metal. Values for aqueous solution will be reviewed first, then the effects of added acid or salts on solubility considered. 

There are commonly accepted experimental standards for the determination of conductivity and specific resistance in aqueous pigment extracts [18]. The electrical conductivity y is calculated from the electrical conductance its inverse is the specific resistance f=l/-y, derived from the electrical resistance. Additional experimental methods have been developed for the determination of soluble sulfates, chlorides, and nitrates [19]. 

ISO 15039 2003 - Textile-glass rovings - Determination of solubility of size... 

McNally, M.E. and Grob, R.L. Headspace determination of solubility limits of the base neutral and volatile organic components from the Environmental Protection Agency s list of priority pollutants, J. Chromatogr. A, 284 105-116, 1984. 

Sobotka, H. and Kahn, J. Determination of solubility of sparingly soluble liquids in water, / Am. Chem. Soc, 53(8) 2935-2938,... 

Chemical stability studies wiU also be conducted on aqueous solutions of the drug at varying pHs and temperatures and in a variety of solvents, experiments that may be coupled with determination of solubility. This information is important for determining the shelf life... 

Thomas, T.A. (1977) An automated procedure for the determination of soluble carbohydrates in herbage. Journal of the Science of Food and Agriculture 28, 639-642. 

A potentiometric method for determination of ionization constants for weak acids and bases in mixed solvents and for determination of solubility product constants in mixed solvents is described. The method utilizes glass electrodes, is rapid and convenient, and gives results in agreement with corresponding values from the literature. After describing the experimental details of the method, we present results of its application to three types of ionization equilibria. These results include a study of the thermodynamics of ionization of acetic acid, benzoic acid, phenol, water, and silver chloride in aqueous mixtures of acetone, tetrahydrofuran, and ethanol. The solvent compositions in these studies were varied from 0 to ca. 70 mass % nonaqueous component, and measurements were made at several temperatures between 10° and 40°C. 

No other solvent extraction process other than the CO2 technology allows such a strong influence on loading, phase equilibrium, and selectivity. Unfortunately, the solubility of extracted substances in CO2 is relatively low, compared with the usual solvents which give absolute miscibility with the extracted valuable materials in most cases. The determination of solubility and solvent ratios is therefore important for the economy of the process. 

As we shall see, the solution conductivity depends on the ion concentration and the characteristic mobility of the ions present. Therefore, conductivity measurements of simple, one-solute solutions can be interpreted to indicate the concentration of ions (as in the determination of solubility or the degree of dissociation) or the mobility of ions (as in the investigations of the degree of solvation, complexation, or association of ions). In multiple-solute solutions, the contribution of a single ionic solute to the total solution conductivity cannot be determined by conductance measurements alone. This lack of specificity or selectivity of the conductance parameter combined with the degree of tedium usually associated with electrolytic conductivity measurements has, in the past, discouraged the development of conductometry as a widespread electroanalyti-cal technique. Today, there is a substantial reawakening of interest in the practical applications of conductometry. Recent electronic developments have resulted in automated precision conductometric instrumentation and applications... 

---