Effect of system variables on solubility

Valery Yu. Senichev, Vasiliy V. Tereshatov Institute of Technical Chemistry Ural Branch of Russian Academy of Sciences, Perm, Russia 

Solubility in solvents depends on varions internal and external factors. Chemical structure, molecular mass of solute, and crosslinking of polymer fall into flie first group of factors, in addition to temperature and pressnre in the second gronp of factors involved. 

The process of dissolution is determined by a combination of enthalpy and entropy factors. The dissolution description can be based on the Flory-Hnggins eqnation. Flory and Huggins calculated the entropy of mixing of long-chain molecules under the assumption that polymer segments occupy sites of a lattice and solvent molecules occupy single sites. 

The theory implies that the entropy of mixing is combinatorial, i.e., it is stipulated by permutations of molecules into solution in which the molecules of mixed components differ greatly in size. The next assumption is that AV ,j,j = 0 and that the enthalpy of mixing does not influence the value of AS i. The last assumptions are the same as in the Hildebrand theory of regular solutions. The expression for the Gibbs energy of mixing is 

The first two terms result from the configurational entropy of mixing and are always negative. For AG to be negative, the value must be as small as possible. The theory assumes that the parameter does not depend on concentration without experimental confirmation. 

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Landell-Ferry Free Volume fwFL> Fluctuation Free Volume uc. ittid Free Volume for Thermal Expansion fa p- The effect of system variables on solubility is discussed in Handbook of Solvents, 2001. Miller (1968) noted that the concept of free volume is easy to grasp, but, quantitatively, its definition runs into snares. Is free volume the specific volume of the liquid (solution) minus the volume of the molecules computed from Van Der Waals radii, or minus the volume swept out by the segments as they rotate, or is it some other volume The free volume is generally, but necessarily, about 2.5% for all polymers. 

However, there are some potential effects of spilled oil on fish. The impacfs on fish are primarily to fhe eggs and larvae, wifh limited effecfs on fhe adulls. The sensitivity varies by species pink salmon fry are affected by exposure to water-soluble fractions of crnde oil, and pink salmon eggs are very tolerant to benzene and water-soluble petroleum. The general effects are difficnlt to assess and document quantitatively, dne to the seasonal and natural variability of the species. Fish rapidly metabolize aromatic hydrocarbons, due to their enzyme system. 

While it is widely realized that pressure is a useful variable for increasing the solubility of the electroactive species and hence the rate of the electrode process, it is mostly forgotten that it is also a variable which affects several of the steps in the overall process. In fact these more subtle effects of pressure on organic electrode reactions do not seem to have been investigated although it is possible to estimate their importance by considering the known effects of pressure on chemical systems (Hamann, 1957). 

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