Preparation of Vitamin C from Lemon Juice

Abstract

The isolation and identification of vitamin C 1 has stimulated research in many laboratories where the crystalline substance is desired. Our original procedure has been successfully followed in other laboratories, but the present detailed procedure can be followed more readily, with larger yields, and in less time. Working with one to 6 liters of lemon juice, consistent yields of 100 to 150 mg. per liter of the crystalline vitamin may be regularly obtained.

Filter 3 1. of juice through muslin, add 7 gm. of copper-free basic lead carbonate (2PbCO₃. Pb(OH)₂) per 100 cc., stir with an electric stirrer for 3 hr., add saturated neutral lead acetate solution (about 500 cc. per 3 1. preparation), continue stirring for 30 min., and centrifuge (ppt. is inactive, but may be rinsed for further recovery). Maintain a stream of CO₂ bubbling through the liquid while cooling to 0°C., add NH₄OH (1:3), with constant stirring, to the liquid until the pH reaches 7.6 (as shown by phenol red on a spot plate), centrifuge, discard the liquid (inactive), redissolve the yellow precipitate with acetic acid (1:3), and reprecipitate with NH₄OH at a pH of 7.6. (If either of the above liquid portions remain yellow, probably not enough lead acetate solution or ammonia was added). Dissolve the precipitate slowly with hydrochloric acid (1:1), adding acid until the solution will turn Congo red distinctly blue. Extract the entire preparation with one-half volume of n-butyl alcohol (to remove oils, etc.) and then add ethyl alcohol until the concentration is about 75%. Centrifuge (ppt. is mostly PbCl₂), evaporate to about 10 cc, add 100 cc. of acetone, centrifuge (ppt. mostly inorganic salts), add enough BaCO₃ to neutralize free HCl (to Congo red), and evaporate to dryness in the presence of fine white sand (about 5 gm.).