What is the difference between lyophobic sol and lyophilic sol?

Ans: Lyophilic sol: The colloidal sols directly formed by mixing substances like gum, gelatin, starch with a suitable liquid (the dispersion medium) are Called lyophilic sols. If the dispersion medium is separated from dispersed phase, the sol can be reconstituted by simply mixing with the dispersion medium. That is why these sols are also called reversible sols. These sols are quite stable and cannot be easily coagulated. 
Lyophobic sols: The colloidal sols like gold do not formed directly by mixing with dispersion medium and can be prepared only by special methods. These are called lyophobic sols. These sols are readily coagulated on the addition of small amounts of electrolytes, or by heating or shaking and hence are not stable. Once coagulated, they do not give back the colloidal sol by simple addition of the dispersion medium. Hence, these sols are called irreversible sols.

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