A catalyst suitable for hydrogenating organic compounds, essentially containing from 65 to 80% of nickel, calculated as nickel oxide, from 10 to 25% of silicon, calculated as silicon dioxide, from 2 to 10% of zirconium, calculated as zirconium oxide, and from 0 to 10% of aluminum, calculated as aluminum oxide, with the proviso that the sum of the content of silicon dioxide and aluminum oxide is at least 15% (percentages in % by weight, based on the total weight of the catalyst), obtainable by addition of an acidic aqueous solution of nickel, zirconium and, if desired, aluminum salts to a basic aqueous solution or suspension of silicon compounds and if desired aluminum compounds, the pH of the mixture thus obtained being decreased to at least 6.5 and then adjusted to from 7 to 8 by addition of further basic solution, isolation of the solid thus precipitated, drying, shaping and calcining, furthermore a process for preparing the catalysts and their use for preparing medicinal white oil, highly pure medicinal paraffins and low-boiling aromatic-free hydrocarbon mixtures.