I will put my question in a simpler way with an example.
The solubility of NaCl in pure water at 25ºC is approximately 6.14 moles/L.
I try to dissolve NaCl at 25ºC in equimolar mixtures (suppose X=0.50) of water + co-solvent and the solubility always decreases a lot (more the more co-solvent there is present).
This was known for aqueous mixtures of methanol, ethanol, propanol, acetone, DMF, etc. (all with lower dielectric constant than water and therefore also the mixture).
Now if I do the same with EC, formamide, N-methyl-formamide, N-methyl-acetamide, N-methyl-acetamide, .... (all with dielectric constant greater than water and therefore the mixture also) the same thing happens.
Does this mean that the dielectric constant of the medium does not influence the solubility?
If I have proven that it influences the ionic association or the primary hydration number, but not the solubility (the solubility product, the increased energy of Gibbs' transference,....) Why?
The same thing happens with all alkaline halides (and I imagine that in the other salts?
Another example to finish: for example, the solubility of NaF in water at 25ºC is 0.983 moles/L. What do I have to do to increase it?
Translated with www.DeepL.com/Translator
Dear Sir. Concerning your issue about the relation between dielectric constant and solubilization . The solubilization of water in various surfactant solutions of chlorinated solvent were investigated in relation to the dielectric constant (ε) of each solvent. As an example of the application of solubilization of polar substances, contamination tests were carried out on cotton and acrylic fabrics by acid dye (Azure Blue V) . 1) A value of ε was unaffected by the addition of surfactants or water into the solvent, while the conductivity (G) increased by the addition of sodium di-2-ethylhexyl sulfosuccinate (DOS), especially in the solvent of high ε. 2) The higher a value of ε, the greater the solubility of water in each solvent. DOS had a high ability to solubilize water and the ability showed minimum at ε ≈ 5, whereas polyoxyethylene monostearate (EOS) showed little water solubilizing effect. 3) The degree of contamination (DOC) by Azure Blue V depended on ε of each solvent and it showed minimum at ε ≈ 7. DOS had a lowering effect of DOC and the effect became more remarkable in the solvent of high ε. I think the following below link may help you in your analysis:
https://www.jstage.jst.go.jp/article/senshoshi1960/22/5/22_5_197/_article
https://www.sciencedirect.com/science/article/pii/S0022354915345597
https://onlinelibrary.wiley.com/doi/pdf/10.1002/jps.2600530905
Thanks
Thank you very much for your quick and kind reply.
Language problems: I don't think you've understood me or I've understood you.
I will further simplify the question: if the solubility of NaCl in water at 25°C is 6.14 mol/L, why does NaCl's solubility in both a mixture (water+methanol) and a mixture (water+formamide) decrease compared to that in pure water?
See for example the attached tables:
Although people have mention "in general" the higher the dielectric constant of the solvent, the higher the solubility of salts in the solvent, there's really been no proper studies about this. The reasoning given is typically as simple as: If you put X mole of salt in Y mL of water, all of the salt will dissolve, but if you put X mole of salt in Y mL of oil, the salt will remain undissolved. Since water has higher dielectric constant than oil, it is assumed that dielectric constant is responsible for this. But there has been no proper study to confirm this. I have seen ionic conductivity studies where LiTf in lower dielectric constant solvents produces higher ionic conductivity than LiTf in higher dielectric constant solvents. If you assume that higher ionic conductivity is because of higher ionic dissociation, then you have to conclude that dielectric constant is not a factor in ionic dissociation (and thus ion solvation).
In your original post, you claim that "...I have proven that it influences the ionic association or the primary hydration number, but not the solubility (the solubility product, the increased energy of Gibbs' transference,...)", I would love to see the proofs.
Dear Mohd Farid Ismail,
Thank you so much for taking the time to answer my question.
I understand what you mean: more salt dissolves in water than in oil because the dielectric constant of water is higher than that of oil. But if we compare the solubility in water with the solubility in formamide, which has a dielectric constant greater than that of water, the salt solubility decreases.
In short, not only does the dielectric constant influence the solubility but other factors such as polarity, density, viscosity, etc.
If you have any bibliography on the subject, it is welcome.
With regard to the relationship between conductivity-solubility-ionic dissociation, I agree. Again, I ask you for literature on the subject.
Finally, on the evidence you are asking for, I do not have it and I do not believe it can be obtained. What I say (perhaps I expressed myself badly) is that the assumptions, conjectures, etc. (many of them suggested by other authors such as T. Mussinni, Y. Marcus, ....) that I make allow me to explain my data. Proofs, proofs, I don't have any!!!
Yours Sincerely
Dr. Felipe Hernández-luis
Hi, you can look at this link.
https://pqdtopen.proquest.com/doc/304488169.html?FMT=ABS
It's a thesis by Dr. Matt Petrowsky (whom I worked with when I was doing my PhD). He's on researchgate too.
While it may be true that solubility might be influenced by other factors, the question is what are they? Certainly it's not dielectric constant (or not dielectric constant only).
Another issue is, finding the relation between solubility to density or viscosity is not very desirable to me (a chemist) because I want a property that is related to molecular structure, so that it will guide me on what molecule to synthesize/pick as the solvent without having to measure the other properties.
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