The Limits of Solubility

The lower members of other homologous series of oxygen compounds— the acids, aldehydes, ketones, anhydrides, ethers and esters—have approximately the same limits of solubility as the alcohols and substitution and branching of the carbon chain has a similar influence. For the amines (primary, secondary and tertiary), the limit of solubility is about C whilst for the amides and nitriles it is about C4. 

The conditions adopted in this procedure favor the production of a-monosulfonate in a state of high purity at the expense of a high conversion of anthraquinone. A better conversion can be achieved by conducting the sulfonation at a higher temperature, or by using more oleum, but in either case there is a considerable increase in the amount of disulfonic acids formed. The extent of /3-sulfonation is not influenced greatly by the temperature, but is dependent chiefly on the amount of mercuric salt present in the solution. The amount specified corresponds approximately to the limit of solubility of the salt in the acid employed, and very little of the /3-acid is formed. As the potassium /S-sulfonate is more soluble than the a-salt, traces of this isomer are easily eliminated by crystallization. 

The limit of solubility typically is around 150 to 175 ppm Si02 in cold water but increases with alkalinity, pH, and temperature to perhaps = 250 ppm. 

In the absence of polymer the sediment volume of silica depends on the non-solvent fraction of the medium as shown in Figure 6. The sediment volume assessment of steric stabilization behavior of the copolymers is illustrated in Figures 7a to 7c. At low styrene contents, both the random and block copolymers show a steady increase in sediment volume as the non-solvent content is raised up to the phase separation value. With polystyrene and random copolymers of high styrene content, the sediment volume stays largely constant with alteration in the non-solvent fraction until the theta-point is approached and then continues to become larger as the limit of solubility is reached. In Figure 7b only the data points of RC 86 are shown, RC 94 giving almost identical values. 

In order to detect the presence of some very specific impurities normally present in the official substances the limits of soluble impurities have been laid down in different pharmacopoeias. Some typical examples are cited below ... 

Evf—V system. — Haefling and Daane [251] have studied the limits of solubility of the rare earths, in uranium and uranium in various rare earths, in the temperature range 1000°—1250° C. About 1.12 wt. per cent of uranium is soluble in europium at 1200° C whereas the solubility of europium in uranium at that temperature is only 0.21 wt. per cent. 

Fig. 6.3 Schematic phase diagram for lamellar PS-PB diblocks in PS homopolymer (volume fraction 0h). where the homopolymer Mv is comparable to that of the PS block (Jeon and Roe 1994). L is a lamellar phase, I, and I2 are disordered phases, M may correspond to microphase-separated copolymer micelles in a homopolymer matrix. Point A is the order-disorder transition.The horizontal lines BCD and EFG are lines where three phases coexist at a fixed temperature and are lines of peritectic points. The lines BE and EH denote the limit of solubility of the PS in the copolymer as a function of temperature.

The limit of solubility is typically around 150 to 175 ppm. This limit should not be exceeded in a cooling system otherwise a glassy, crystalline scale can be laid down, which is an extremely efficient barrier to heat transfer and requires special and expensive techniques for its removal. 

Under these circumstances, the limit of solubility of calcium sulfate can easily be exceeded and deposition results. 

In the preceding chapter we have been considering the equilibrium of two phases of the same substance. Some of the most important cases of equilibrium come, however, in binary systems, systems of two components, and we shall take them up in this chapter. Wo can best understand what is meant by this by some examples. The two components mean simply two substances, which may be atomic or molecular and which may mix with each other. For instance, they may be substances like sugar and wrater, one of which is soluble in the other. Then the study of phase equilibrium becomes the study of solubility, the limits of solubility, the effect of the solute on the vapor pressure, boiling point, melting point, etc., of the solvent. Or the components may be metals, like copper and zinc, for instance. Then we meet the study of alloys and the whole field of metallurgy. Of course, in metallurgy one often has to deal with alloys with more than two components—ternary alloys, for instance, with three components—but they arc considerably more complicated, and we shall not deal with them. 

Solution The isotherms on an Hx diagram for a system such as NaOH/H terminate at points where the limit of solubility of the solid in water is reached. Th the isotherms in Fig. 13.12 do not extend to a mass fraction representing pure NaO How, then, is the basis of the diagram with respect to NaOH selected In the of the water the basis is HH]Q = 0 for liquid water at 32( F), consistent with the b of the steam tables. For NaOH the basis is HNa0n = 0 for NaOH in an infini dilute solution at 68(°F). 

Although the methyl silicone oils are soluble in benzene and in the lighter hydrocarbons, they are only partially soluble in alcohol and in the heavy hydrocarbons. The relative insolubility in petroleum lubricating oil may be the reason for the success of silicone oils in suppressing foam in certain engine oils at the limit of solubility the silicone may set up a high local concentration at the oil-air interface and so exercise a surface-active effect. Whatever the mechanism, a very... 

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