New cholesterol reagent.

R ECENTLY a new reagent was proposed for the determination of cholesterol (1, 2). This reagent was purported to be saturated ferrous sulfate in glacial acetic acid. Since it has been reported that ferrous sulfate is qualitatively insoluble in anhydrous acetic acid (3, 4) and that ferrous iron is “subject to pronounced air oxidation in glacial acetic acid” (5), it was felt that several factors should be investigated concerning the reagent. These factors are as follows: 1. The solubility of ferrous sulfate in glacial acetic acid under the described conditions (2) 2. The stability of this ferrous ion in the same system 3. The solubility of ferric sulfate in glacial acetic acid under identical conditions, since this compound is suspected of being the active agent in this reaction 4. The reaction spectra for cholesterol with both ferrous and ferric sulfate solutions