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25 g Cr(VI)O3 is dissolved in 25 mL H2SO4 (conc.). Solution is added very slowly to 75 mL H2O that had been cooled to 0oC and is stirring.
From Professor Al Hagedorn:
This recipe for Jones reagent should work well for simple cases, but likely has a bit too much acid for really delicate ones. The ratio of "H+" to CrO3 should be 3:1, as required by the stoichiometry for alcohol to ketone oxidation.
I like 2.67 Molar CrO3 in 3.00 Molar H2SO4 (i.e., 8.00 Normal). It doesn't need analytical chemistry precision, but I've had good results with a reasonably good titration of the H2SO4, and drying the CrO3 in advance. Titrating the substrate with this sauce, I've been able to oxidize secondary alcohols without hurting tertiary pseudoaxial alcohols benzylic to activated aromatic rings; it doesn't take much excess acid to mess those up...