A method of chemical mechanical polishing a surface of a substrate comprising the step of: contacting said substrate and a composition comprising: (i) a plurality of colloidal silica particles having less than 200 ppb of each trace metal impurity, excluding potassium and sodium, have less than 2 ppm residual alcohol and wherein the cumulative trace metal concentration, excluding potassium and sodium, is in the range from 0.5 to 5 ppm; and (ii) a medium for suspending said particles; wherein said composition is an ultrapure colloidal silica dispersion; and wherein said contacting is carried out at a temperature and for a period of time sufficient to planarize said substrate, wherein said colloidal silica particles are prepared by a process comprising the steps of: dissolving a fumed silica in an aqueous solvent comprising an alkali metal hydroxide to produce a alkaline silicate solution; removing said alkali metal via ion exchange to convert said alkaline silicate solution to a silicic acid solution; adjusting temperature, concentration and pH of said silicic acid solution to values sufficient to initiate nucleation and particle growth; cooling said silicic acid solution at a rate sufficient to produce a colloidal silica dispersion; and isolating said colloidal silica particles from said colloidal silica dispersion to produce colloidal silica particles having a mean or aggregate particle size 10 nm to 200 nm. contacting said substrate and a composition comprising: (i) a plurality of colloidal silica particles having less than 200 ppb of each trace metal impurity, excluding potassium and sodium, have less than 2 ppm residual alcohol and wherein the cumulative trace metal concentration, excluding potassium and sodium, is in the range from 0.5 to 5 ppm; and (ii) a medium for suspending said particles; (i) a plurality of colloidal silica particles having less than 200 ppb of each trace metal impurity, excluding potassium and sodium, have less than 2 ppm residual alcohol and wherein the cumulative trace metal concentration, excluding potassium and sodium, is in the range from 0.5 to 5 ppm; and (ii) a medium for suspending said particles; wherein said composition is an ultrapure colloidal silica dispersion; and wherein said contacting is carried out at a temperature and for a period of time sufficient to planarize said substrate, wherein said colloidal silica particles are prepared by a process comprising the steps of: dissolving a fumed silica in an aqueous solvent comprising an alkali metal hydroxide to produce a alkaline silicate solution; removing said alkali metal via ion exchange to convert said alkaline silicate solution to a silicic acid solution; adjusting temperature, concentration and pH of said silicic acid solution to values sufficient to initiate nucleation and particle growth; cooling said silicic acid solution at a rate sufficient to produce a colloidal silica dispersion; and isolating said colloidal silica particles from said colloidal silica dispersion to produce colloidal silica particles having a mean or aggregate particle size 10 nm to 200 nm. dissolving a fumed silica in an aqueous solvent comprising an alkali metal hydroxide to produce a alkaline silicate solution; removing said alkali metal via ion exchange to convert said alkaline silicate solution to a silicic acid solution; adjusting temperature, concentration and pH of said silicic acid solution to values sufficient to initiate nucleation and particle growth; cooling said silicic acid solution at a rate sufficient to produce a colloidal silica dispersion; and isolating said colloidal silica particles from said colloidal silica dispersion to produce colloidal silica particles having a mean or aggregate particle size 10 nm to 200 nm.