Limit 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. 

Depending on the type and charge of electrolyte, its concentration, and the temperature, a limit of solubility exists for every surfactant in an electrolyte-containing solution. This limit of solubility often lies at higher concentrations for phosphorus-containing surfactants than for most other ones. 

Many substances that participate in aqueous reactions are soluble salts. These ionic solids dissolve in water to give solutions of cations and anions. For almost all salts, there is an upper limit to the amount that will dissolve in water. A salt solution is saturated when the amount dissolved has reached this upper limit of solubility. Any additional salt added to a saturated solution remains undissolved at the bottom of the vessel. When excess solid... 

Figure 6.10 High-throughput solubility-pH determination of chlorpromazine. The horizontal line indicates the set upper limit of solubility, where the compound completely dissolves and solubility cannot be specified. The points below the horizontal line are measured in the presence of precipitation and indicate solubility. The solubility pH curve was collected in the presence of 0.5 vol% DMSO, and is affected by the cosolvent (see text). [Avdeef, A., Cun Topics Med. Chem., 1, 277-351 (2001). Reproduced with permission from Bentham Science Publishers, Ltd.]...

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. 

Banerjee, S., Yalkowsky, S.H., Valvani, S.C. (1980) Water solubility and octanol/water partition coefficient of organics. Limitations of solubility-partition coefficient correlation. Environ. Sci. Technol. 14, 1227-1229. 

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 ... 

Doses selected for safety pharmacology studies are typically based on the criteria established in the ICH S7A guidance.25 Doses should exceed those projected for clinical efficacy and at the upper limit be bound by (1) adverse pharmacodynamic effects in the safety pharmacology study (2) moderately adverse effects in other non-clinical studies that follow a similar route and duration of dosing or (3) limit of solubility/toxicity. In the absence of adverse effects, the maximum administrable dose can be used. If nonreusable animals enter the study, then the maximum tolerated dose may be appropriate. Most importantly, the doses/concentrations should establish the dose/concentration-response relationship of the adverse effect. 

The cloud point may be regarded as a limit of solubility, since the turbidity produced is due to HPMC precipitating from solution. Equation (2) was used to determine the effect of salt concentration on the cloud point. Thus,... 

The substance does not form saturated solutions in a single solvent, hence it has no limits of solubility in the usual sense of this term as applied to crystalline bodies. A solution resembling in its properties a saturated one can be prepared by means of a binary solvent, where a liquid immiscible with nitrocellulose is one of the two components (e.g. acetone and water). 

The rheological properties of all HMHEC polymers are profoundly affected by the hydrophobe molar substitution (MS) and the hydrophobe chain length. For any given hydrophobic moiety, there is a threshold hydrophobe MS below which there are no significant associative interactions. The most common phenomenological evidence for associative behavior is a dramatic increase in the solution viscosity of HMHEC polymers as a function of hydrophobe MS. The solution viscosity of HMHEC polymers continues to increase as a function of hydrophobe MS until the maximum limit of solubility is reached, as which point the HMHEC polymer becomes insoluble in water.33... 

Fig. 6. Upper temperature limit of solubility in salt solution. Resin concentration is 5.0 wt % (10).

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. 

The solubility of polymers is, for thermodynamic reasons, more restricted than the solubility of low-molecular compounds and, consequently, the choice of solvents is limited. Potential solvents for most synthetic polymers are of moderate polarity. Alcohols and liquids of similar polarity are precipitants for many synthetic polymers. The search for a mobile phase that enables RPC through solvophobic interactions between the polymer and the nonpolar stationary phase requires attempts to make the mobile phase an unfavorable environment for the solute. This easily conflicts with the narrow limits of solubility of the polymer under investigation. Solubility effects are known to occur even in low-molecular RPC 92 94), but in polymer RPC they even may govern retention. 

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