Quote Originally Posted by Jorge
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A colloid can be thought as an emulsion but in this case the particles are small enough that surface effects become an important part of their behavior and they still have phase separation.An example would be milk of magnesia.

A solution is made of two or more miscible components with no phase separation, as is the case of sugar in water. Pt/pd, Van Dyke brown and silver salts in liquid gelatin are nothing more than solutions, they are NOT colloids or emulsions. Once they have gone through a chemical reaction they simply become solids embedded in other solids as is the case of silver papers, or they become solids deposited on other solids as is the case of pt/pd or VDB.

Furthermore the exclusionary condition of a semi permeable membrane is erroneous and misleading, ionic material in SOLUTION can and will be rejected by a semi permeable membrane depending on the size of the atom, type of membrane and physical conditions applied to the separation technique. This is best exemplified by the water purification technique of Reverse Osmosis.
Quite accurate, Jorge. In addition, we should mention that the active layer on film and paper is technically a suspension. Also there is, as you pointed out, a differeince between a semi-permeable membrane (ro) and an ion exchange membrane (water conditioning et c.) which _will_ transfer ionic material (along with some non-ionic stuff).

Your acumen, as usual, is appreciated, dr bob.