Solubility behaviour

The azides are salts which resemble the chlorides in solubility behaviour, for example silver azide, AgNj, is insoluble and sodium azide, NaN3, soluble in water. Sodium azide is prepared by passing dinitrogen oxide over molten sodamide ... 

Study of the solubility behaviour of the compound. A semi-quantitative study of the solubility of the substance in a hmited number of solvents (water, ether, dilute sodium hydroxide solution, dilute hydrochloric acid, sodium bicarbonate solution, concentrated sulphuric and phosphoric acid) will, if intelligently apphed, provide valuable information as to the presence or absence of certain classes of organic compounds. 

It will be observed that halogen compounds are not listed separately, but appear in each of the seven groups in accordance with their solubility behaviour. Similarly, certain compounds containing N or S will fall in Groups I-IV (see preceding Section). 

Hydrolysis of a nitrile to an amide. Warm a solution of 1 g. of the nitrile benzyl cyanide) in 4 ml. of concentrated sulphuric acid to 80-90°, and allow the solution to stand for 5 minutes. Cool and pour the solution cautiously into 40 ml. of cold water. Filter oflT the precipitate stir it with 20 ml. of cold 5 per cent, sodium hydroxide solution and filter again. RecrystaUise the amide from dilute alcohol, and determine its m.p. Examine the solubility behaviour and also the action of warm sodium hydroxide solution upon the amide. 

Franks, F. (1966) Solute-water interactions and the solubility behaviour of long-chain paraffin hydrocarbons. Nature 210, 87-88. 

May, W.E. (1980) The solubility behaviour of polycyclic aromatic hydrocarbons in aqueous systems. Petroleum Mar. Environ. Adv. Chem. Ser. 185, Chapter 7, Am. Chem. Soc., Washington DC. 

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. 

The use of thermodynamic models to correlate and predict solubility behaviour in both single solvents and mixtures can be beneficially applied at this point. This technique both validates the experimental data and minimizes the experimental workload for the design of an optimized process. These techniques are discussed further in section 5. 

The application of thermodynamic models to the correlation and prediction of pharmaceutical solubility behaviour is an underutilized technique in today s process research and development environment. This is due to the relatively poor accuracy and limited predictive ability of the previous generation of models. Recent advances in computational chemistry and an increased focus on the life science sectors has led to the development of more appropriate models with significantly improved predictive capabilities. The NRTL-SAC and Local UNIFAC approaches will be discussed here with additional examples given in section 8. 

Solubility Behaviour of Cellulose-Reinforced Starch-PVA Blends with Insertion of Fly-Ash... 

Techniques are available for estimating binary and multi-component solubility behaviour. One example is the van t Hoff relationship which, as stated by Moyers and Rousseau(25), takes the following form for an ideal solution ... 

Solubility behaviour in aqueous solutions is a crucial factor in many aspects of biodegradation because almost all living organisms are dependent on the availability of sufficient water phase. A low molecular weight PVA molecule shows a good solubility in water, be it only in molecular amounts or in bulk quantities. 

Different surfactants are usually characterised by the solubility behaviour of their hydrophilic and hydrophobic molecule fraction in polar solvents, expressed by the HLB-value (hydrophilic-lipophilic-balance) of the surfactant. The HLB-value of a specific surfactant is often listed by the producer or can be easily calculated from listed increments [67]. If the water in a microemulsion contains electrolytes, the solubility of the surfactant in the water changes. It can be increased or decreased, depending on the kind of electrolyte [68,69]. The effect of electrolytes is explained by the HSAB principle (hard-soft-acid-base). For example, salts of hard acids and hard bases reduce the solubility of the surfactant in water. The solubility is increased by salts of soft acids and hard bases or by salts of hard acids and soft bases. Correspondingly, the solubility of the surfactant in water is increased by sodium alkyl sulfonates and decreased by sodium chloride or sodium sulfate. In the meantime, the physical interactions of the surfactant molecules and other components in microemulsions is well understood and the HSAB-principle was verified. The salts in water mainly influence the curvature of the surfactant film in a microemulsion. The curvature of the surfactant film can be expressed, analogous to the HLB-value, by the packing parameter Sp. The packing parameter is the ratio between the hydrophilic and lipophilic surfactant molecule part [70] ... 

Finally, it must be remembered that the hydration is also influenced by the structure of the ion. In view of the fact that the positive pole of a water molecule attaches itself to the negative ion, the molecule will be repelled by the positive nucleus of the positive ion. This means that the ion of a strong acid has a small hydration energy and will therefore have a smaller heat of solution and hence the tendency to form insoluble compounds. This effect is shown when CIOT combines with a large ion, and must be taken into account in explaining the solubility behaviour of caesium salts, which... 

Distinctly different is the solubility behaviour of poly(a-phenylethyl isocyanide), which can be dispersed truly by thermodynamic mixing. It is soluble is more than 40 solvents, as shown in the mode of representation following Hansen s treatment (27), (Fig. 5). The well known Hildebrand-Scott solubility parameter by this treatment is divided into three indices which separately account for cohesive energy contributions from dispersion, permanent dipole-dipole, and hydrogen bonding forces. Thus, the conventional Hildebrand-Scott parameter equals 9.56 (cal/cm3) for an unfractionated sample of poly(a-phenylethyl iso-... 

Other compounds, containing sulphur or nitrogen, may be present in some oils (like onion, garlic).Investigations on the solubility of pure essential-oil components in carbon dioxide showed that the separation of terpene hydrocarbons and oxygenated derivatives by fractionated extraction is difficult, since their solubility behaviours and vapour pressures are almost the same. Saturating the CO2 with water as modifier can increase the differences in solubility [78],... 

When a mixture of a specified amount of a given solute and a specified amount of a given solvent forms a homogeneous liquid, the former is said to be soluble in the latter. The arbitrary standard employed in this book is 0.10g of solid or 0.20 ml of liquid to 3.00 ml of solvent. The study of the solubility behaviour of an unknown substance in various liquids, viz. water, ether, 5 per cent sodium hydroxide solution, 5 per cent sodium hydrogen carbonate solution, 5 per cent hydrochloric acid and cold concentrated sulphuric acid, may provide useful preliminary information about the nature of the compound. 

Table 9.1 Classification of organic compounds according to solubility behaviour...

The solubility behaviour of an unknown compound will serve to classify it into one of the three main divisions, namely, acidic, basic or neutral. This information, supplemented by elemental analysis if deemed necessary, and as noted above cross-correlated with spectroscopic inferences, forms the basis for the subsequent systematic search to identify definitively the functional group or groups present. It cannot be too clearly emphasised that inexperience in spectroscopic interpretation can lead to erroneous conclusions of structure. The value of chemical tests is that they reduce the chance of this happening, furthermore they are frequently easily and quickly performed and provide experience in accurate and reliable observation and reporting. 

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