Gibbs Free Energies, Enthalpies and Entropies of Transfer for Reference Ions Ph4 As and Ph4 B in Mixed DMFA-H2O Solvents at Different Temperatures

The thermodynamic data ( ∆ Gt , ∆ Ht and T ∆ St ) of transfer for tetraphenylarsonium-tetraphenylborate (Ph4AsBPh4) from water to mixed dimethylformamide (DMFA)-H2O solvents were estimated from the experimental solubility and calorimeter measurements. The experiments were done at three different temperatures 288.15, 298.15 and 308.15 K. Also the thermodynamic parameters were divided into reference anion and cation following the asymmetric deviation and their values, were discussed. Dividing all the thermodynamic functions between the cation and anion by using 1.064 factors we obtain their individual functions. The reference ion values can be easily used for evaluating the different thermodynamic parameters of any ion that contains in its counterion tetraphenyl cation or anion . By using the data given here the thermodynamic parameters for some single ion can be estimated for following their behaviour in environment. The single ion thermodynamics are helpful for predicting, explaining and mechanisms suggesting. Theoretical and engineering chemistry are in need for experimental single ion parameters for the comparison with that calculated by different solvation theories.


Introduction
Single ion transfer Gibbs energies, entropies and enthalpies play an important role in many areas of chemistry, such as the estimation of solubilities, electrochemical potentials, distribution ratio and complex formation constants [1].
Extra thermodynamic models must be used for the determination of single ion thermodynamic quantities [2,3].
As one of the extrathermodynamic assumptions, the refrence electrolytes such as tetrphenylphosphonium , tetraphenylarsonium and triso -amyl -n-butylammoniumtetra phenyl borate have been used for the partition of thermodynamic quantities of electrolytes into values of individual ions [4 -6] . Also thermodynamics of ion association are in need to the single ion parameters [7].
The reference electrolyte Ph 4 AsBPh 4 with its caution and anion of different sizes and large tetrahedral structure in which the central ion is buried in four phenyl rings, provide the possibility of evaluating single ion thermodynamic quantities in different solvents [8].
This reference electrolyte assumption has been studied experimentally as well as theoretically in many pure solvents [9], and mixed solvents [10]. Here in this work the Gibbs energies, enthalpies and entropies of transfer for Ph 4 As BPh 4 from water to mixed DMFA-H 2 O solvents were experimentally determined at 288.15, 298.15 & 308.15 K and their values were discussed. The aim of the work is to give data about the solvation of very important reference electrolyte Ph 4 AsBPh 4 in mixed DMFA-H 2 O solvents and its ions, necessary for the evaluating other single ion thermodynamic parameters. These data can help the analyst for further evaluation and discussion about ion properties in solutions.

Experimental
The DMFA used was of spectroscopic purity (Uvasol) from Merck and used directly without purification. Ph 4 AsBPh 4 was prepared by the condensation of aqueous solutions of Ph 4 AsPh 4 B and NaBPh 4 followed by crystallization in acetonitrile as described in ref. 15. The effect of temperature was studied by shaking samples put in closed test tubes in a shaking water bath of the types "Assistant" till saturation for one week at the studied temperatures 288.15, 298.15 and 308.15 K. The solubilities were determined as explained before in ref. 12. Calorimeter like thermos shape (RMG) type 489/10 was used for measuring the enthalpies of solvation at the used temperature. The solubility were determines conductometically and gravimetrically as explained before which are ease, reproducible and cheap methods . Also it consumes little time and accurate data.

Gibbs Free Energies
The calculated ∆ G t and their transfer values ( ∆ G t ) for Ph 4 AsBPh 4 at 288.15, 298.15 and 308.15 K were evaluated as explained in ref. 12 and their values are listed in Tables1-3 with standard deviation of ± 0.3 KJ/mole.

Enthalpies and Entropies
The enthalpies ∆ H t from water to mixed DMFA-H 2 O solvents for the reference electrolyte (RE) Ph 4 As B Ph 4 were estimated calorimetrically at 288.15, 298.15 and 308.15 K and their values are given in Tables 1-3 also. The entropies T ∆ S and entropies of transfer T ∆ S t for Ph 4 AsBPh 4 were obtained by applying equation 1, and their values are also presented in Tables 1-3 [13 -18].
For evaluating the single ion reference thermodynamic parameters for Ph 4 As + & Ph 4 Bwe must use the R ratio, which is the thermodynamic parameters for each reference ion, equation 2.
The average R value on using the Gibbs free energies for both cation and anion is 1.064 ± 0.05 as given in ref. 8.
Dividing all the thermodynamic functions between the cation and anion by using 1.064 factors we obtain their individual functions which cited in Tables 1, 2 and 3. The reference ion values given in Tables 1-3 can be easily used for evaluating the different thermodynamic parameters [19 -25] of any ion that contains in its counter ion tetra phenyl cation or anion at different temperatures.

Conclusions
This work is to give data about the solvation of very important reference electrolyte Ph 4 AsBPh 4 in mixed DMFA-H 2 O solvents and its ions, Ph 4 As + , Ph 4 Bnecessary for the evaluating other single ion thermodynamic parameters. These data can help the analyst for further evaluation and discussion about ion properties in solutions.