6
$\begingroup$

There was a similar question asked here on Chem SE, but the answer was not very satisfactory to me, so I am asking a fresh question.

Peptization is the process of creating a colloid from a precipitate by shaking it with a suitable electrolyte. In this process, the rule of preferential adsorption is followed which states (source) that:

The Particle Constituting the Dispersed Phase adsorb only those ion preferentially which are more related chemically to it or which are common with the Lattice ion of Dispersed phase

So what is the reason behind this selectivity? I think it might have to do with the lattice of the precipitate, because the precipitate is in a solid-state and even after being dispersed it will also remain in the solid-state but as small particles.

So, do the lattice ions try to extend their lattice by adsorption and in this process get separated into small particles? Lattice ion adsorption puts little strain on the lattice structure, because having a similar dimension they simply fit into the gaps in the edges of the crystal, whereas ions other than lattice ions will create some distortion because of its dissimilar dimension?

I found a paper related to this and according to this paper size and deformation of lattice can play an important role in adsorbtion of ions

Fajans and Erdey-Grdz (7) pointed out that in addition to solubility other factors, such as deformation, size of the adsorbed ions, and dissociability of the adsorption complex formed have to be taken into

ADSORPTION ON IONIC LATTICES 1029 account. Moreover, the charge (valence) of the adsorbed ions and the deformability of the lattice ions will play a part. Considering the many factors that influence the adsorbability, it is quite plausible that the socalled Paneth-Fajans-Otto Hahn rule can be only of a highly approximate character.

Reference

I.M. Kolthoff, "Adsorption on Ionic Lattices", J. Phys. Chem., 1936, 40(8), 1027–1040, (Link to the article)

Improve this question
$\endgroup$
4
  • 6
    $\begingroup$ Mention the reason for downvote , please $\endgroup$
    – Samardeep singh
    Commented Aug 26, 2021 at 1:13
  • 5
    $\begingroup$ Numerous reasons: (1) Improper use of boldface emphasis; (2) improper capitalization, both upper and lower; (3) linking a Quora question as a "source"; (4) improper punctuation, including comma, period, and question mark abuse; (5) almost completely incoherent word salad of a post; and (6) a very clear indication that you expect to get something without investing a modicum of effort here. Welcome so chem.SE. Read the rules. Tour the site. $\endgroup$
    – Todd Minehardt
    Commented Aug 26, 2021 at 2:01
  • 2
    $\begingroup$ @Samardeepsingh Please note the edits in the reference section. There is no need to put the whole reference in bold font, and it's good to follow common referencing styles. $\endgroup$
    – S R Maiti
    Commented Sep 1, 2021 at 4:16
  • $\begingroup$ @Samardeepsingh, What does the Kolthoff's article say? I don't know the exact reason, but must be related to fitting of the ion in the crystal structure. Don't worry too much about downvotes. It is a disease. $\endgroup$
    – ACR
    Commented Sep 6, 2021 at 21:07

0

Reset to default