Re: free ions versus salts (was alum and aluminum)

[Guest guest]

wrote:

> 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.

Interesting stuff Chris. Thanks.

~~ Jocelyne