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Sols are lyophobic (solvent hating) suspensions of solid particles (1 to 1000 nanometres in size) in a liquid. They may be prepared by dispersion or condensation. Dispersion techniques include grinding the solids to colloidal dimensions in a ball mill (dry/wet) and Beidig's arc method. Condensation or precipitation methods work by making the colloidal particle come out of solution into the colloidal phase, either by addition of a precipitating agent (salt) or by change of temperature. Stability of the sols prepared may be maintained by using dispersing agents
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