`=>` Depending upon the nature of interaction between the dispersed phase and the dispersion medium, colloidal sols are divided into two categories
(i) Lyophilic (solvent attracting)
(ii) Lyophobic (solvent repelling).
● If water is the dispersion medium, the terms used are hydrophilic and hydrophobic.
(i) `text(Lyophilic Colloids :)` The word ‘lyophilic’ means liquid-loving.
● Colloidal sols directly formed by mixing substances like gum, gelatine, starch, rubber, etc., with a suitable liquid (the dispersion medium) are called lyophilic sols.
● An important characteristic of these sols is that if the dispersion medium is separated from the dispersed phase (say by evaporation), the sol can be reconstituted by simply remixing with the dispersion medium. That is why these sols are also called reversible sols.
● Furthermore, these sols are quite stable and cannot be easily coagulated as.
(ii) `text(Lyophobic Colloids :)` The word ‘lyophobic’ means liquid-hating.
● Substances like metals, their sulphides, etc., when simply mixed with the dispersion medium do not form the colloidal sol.
● Their colloidal sols can be prepared only by special methods. Such sols are called lyophobic sols.
● These sols are readily precipitated (or coagulated) on the addition of small amounts of electrolytes, by heating or by shaking and hence, are not stable.
● Further, once precipitated, they do not give back the colloidal sol by simple addition of the dispersion medium. Hence, these sols are also called irreversible sols.
● Lyophobic sols need stabilising agents for their preservation.
`=>` Depending upon the nature of interaction between the dispersed phase and the dispersion medium, colloidal sols are divided into two categories
(i) Lyophilic (solvent attracting)
(ii) Lyophobic (solvent repelling).
● If water is the dispersion medium, the terms used are hydrophilic and hydrophobic.
(i) `text(Lyophilic Colloids :)` The word ‘lyophilic’ means liquid-loving.
● Colloidal sols directly formed by mixing substances like gum, gelatine, starch, rubber, etc., with a suitable liquid (the dispersion medium) are called lyophilic sols.
● An important characteristic of these sols is that if the dispersion medium is separated from the dispersed phase (say by evaporation), the sol can be reconstituted by simply remixing with the dispersion medium. That is why these sols are also called reversible sols.
● Furthermore, these sols are quite stable and cannot be easily coagulated as.
(ii) `text(Lyophobic Colloids :)` The word ‘lyophobic’ means liquid-hating.
● Substances like metals, their sulphides, etc., when simply mixed with the dispersion medium do not form the colloidal sol.
● Their colloidal sols can be prepared only by special methods. Such sols are called lyophobic sols.
● These sols are readily precipitated (or coagulated) on the addition of small amounts of electrolytes, by heating or by shaking and hence, are not stable.
● Further, once precipitated, they do not give back the colloidal sol by simple addition of the dispersion medium. Hence, these sols are also called irreversible sols.
● Lyophobic sols need stabilising agents for their preservation.