free ions versus salts (was alum and aluminum)

[Guest guest]

For Jocelyne or anyone else interested,

It is an interesting philosophical question whether the difference between an

elemental form of an element and an ionic form is attributable to the ionic

form's existence as a salt or strictly to its own identity as an ion-- that is,

its different number of electrons from the elemental form.

While a salt may dissolve completely in a solution and thereby yield free

ions not linked in salt linkages, in a certain way the identity of the free ion

is dependent on its existence as a salt outside of solution, and a potential

precipitate pending changes in its environment. Free chloride, for example,

cannot itself be added to a solution, and electric neutrality requires it be

balanced by an equal positive charge.

However, I would suggest that several points allow us to divorce the

indentity of the salt or hypothetical salt potential from the identity of the

free ion:

1) The free anion's unique chemical behavior is independent of the cation it

is associated with in solution. Free chloride will behave the same in a

solution of sodium chloride as in a solution of potassium chloride, while in

both

cases the behavior of free chloride is fundamentally different from that of

elemental chlorine, whether as a diatomic gas or a free radical.

2) If two salts of different cations but the same anions are added to a

solution, the free anions are not distinguishable based on which cation they

were

previously associated with, nor by their potential to form a precipitate with

one or the other specific cations. Take again sodium and potassium chloride.

If they are added together to the same solution, the free chloride ions cannot

be distinguished as to whether they " belong " to sodium or potassium, and it

cannot be predicted which cation they will precipitate with under precipitating

conditions based on which cation they were associated with before

dissociation.

Thus, there is no real ontological existence to the hypothetical salt

*potential* of these ions in solution. They, ontologically, cease to be ionic

compounds in solution.

3) In the body, ions exist mostly as free ions rather than salts (I say

mostly because salt linkages exist in other contexts but for the purposes here

they

essentially do not exist), but the free ions are completely independent of

any such hypothetical salt partners, existing in independent solutions.

For example, much of the chloride taken into the body exists as sodium

chloride and almost none of it exists as hydrogen chloride or hydrochloric acid,

yet

most of the chloride in the stomach is electrically neutralized by hydrogen,

and the same is true in the urine, while sodium exists elsewhere often not

associated with chloride. Thus the free chloride (or other ions) exists as an

independent unit, not a salt formation, nor as an entity whose identity is

dependent on a previous or hypothetical potential salt.

Indeed, hydrogen chloride is not even a true salt, as, not in solution (that

is, in any case where it could exist as a united compound), it is a covalent

linkage. Yet chloride associated with hydrogen does not possess a different

chemical identity from chloride associated with sodium, once again showing

chloride's identity to be self-contained in its existence as chloride, and not

dependent on its existence as a salt or its potential existence as a salt.

Chris

____

" What can one say of a soul, of a heart, filled with compassion? It is a

heart which burns with love for every creature: for human beings, birds, and

animals, for serpents and for demons. The thought of them and the sight of them

make the tears of the saint flow. And this immense and intense compassion,

which flows from the heart of the saints, makes them unable to bear the sight of

the smallest, most insignificant wound in any creature. Thus they pray

ceaselessly, with tears, even for animals, for enemies of the truth, and for

those

who do them wrong. "

--Saint Isaac the Syrian