An Industrial Steam Distillation
Frederick S. Potter and Conrad Schuerch SUNY
Separation of rosin and turpentine from pine gum
Syracuse 13210
The technique of codistillation, usually steam distillation, is still a useful method for the separation of suhstances of low volatility from nonvolatiles. As such it continues to deserve a place in lower division chemistry courses. The principle on which it is based is treated in elementary organic laboratory texts.Wonsidering the high proportion of chemists and related technical personnel whose major responsibilities deal with the preparation, characterization, isolation, analysis, or formulation of mixtures and who rarely work with pure compounds, one can easilv iustifv the inclusion of selected ex~eriments dealing w i t i such materials in a lower division course although they are rarely included. The following experiment was ~ e v e l o ~ etod pro&de such an experience and-is modified from a n analytical method provided by Ray V. Lawrence. Chief. Naval Stores Lahoratorv. U.S.D.A.. P.O. Box 1, ~lust'ee,Florida 32072. Our s t u c h s have Iv had some satisfaction in convertine a tackv intractable mass-pine gum=-into two recognizable and useful materials-a fragrant water-white liquid, turpentine and a hard amher-colored resin, rosin. The experiment and clean-up can he easily accomplished in a three-hour lahoratory period.
sures of pure water and the pure codistilling substance equals atmospheric pressure. However the amounts of water and codistillate are proportional to the vapor pressures of water and the organic material and the vapor pressure of pure turpentine even a t 1M)"C is quite small. Therefore the proportion of turpentine distilling with steam a t or near the boiling point of water is tw, small for practical separations. However by carrying out a steam distillation a t somewhat higher temperature, 130-140°C. the vapor pressure of the organic material is substantially increased and the ratio of turpentine to water distilling reaches practical limits. This method of superheated steam distillation is generally useful to separate compounds of low volatility from intractable nonvolatile resins or tars. Apparatus one 500-mlthree-neckedflask one gas entry tube two 2WC thermometers one long or two 20-cm condensers one distilling head two adapters elasscol heater) one oil or sand bath (or n~~ I(X1-ml yraduated cylinder or hake;, separatory funnel, widenecked funnel. screw or pinch clamp. nlumrnum ueighmc pans ~
The Experiment Turpentine and rosin are two important articles of commerce. Tumentine is used as a solvent and as a n intermediate in the formation of perfumes, flavoring materials, and heat- and pressure-sensitive adhesive resins. Rosin is used as a n intermediate in the orenaration of industrial . soaps:and film-forming polymers for paints and enamels. Turoenrine and rosm are obtained from living Sourhem pine.irees by slashing the hark, treating the &shes with acid to keep the wound open, and collecting the pine gum. The pine gum is steam-distilled at elevated temperatures (actually "superheated steam"), and the material separates cleanly into a volatile fraction "gum turpentine" that codistills with steam, and a nonvolatile fraction "eum rosin." Both ~ r o d u c t sare usuallv used as mixtures h i t they can he furtGer separated into thkir components. Wood tur~entine.a similar product. is ohtained hv extraction of ihippedpine stumps. The kxtract contains the largely hydrocarbon cut, turpentine, some less volatile terpene alcohols known as pine oil, and rosin. Sulfate turpentine is ohtained as a by-product of the pulping of pine wood hv the kraft Drocess.. toeether with a nonvolatile fraction; tall oil, der&ed from rosin. Other species of everereens Droduce turpentines which differ somewhat in their composition. This experiment demonstrates the separation of pine eum into turnentine and rosin hv means of codistillation k t h steam a; temperatures above 1M)"C. Turpentine cannot he separated from Dine eum hv simple distillation hecause of its low volatility, unless e k e s s k e heat or heating time is used. The last portion of the turpentine is a t too low a mole fraction to have significant vapor pressure. Steam distillation in contrast takes advantage of the vapor pressure of the pure liquid, and distillation occurs at the temperature a t which the sum of the vapor pres-
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672 / Jownal of Chemical Education
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Experimental About 100 g of crude pine gum is poured into a 5M)-ml threenecked flask. A gas entry tube far steam and a 200°C thermometer are placed in the two side necks, and are inserted below the level of the gum. The flask is placed in an oil bath set for heating. A distilling head is placed in the center neck and one long or two 20-cm condensers are attached to it in series. An adapter is fastened to the second condenser. Make sure all are securely clamped. The house steam line is connected through a mbher hose to s water trap made from a simple adapter, tubing, and pineh clamp, and the water trap is then connected to the gas entry tube so that dry steam can be introduced into the flask. Before turning on the steam, the oil bath should be heated to nearly 200'C, (the temperature should be measured with a second thermometer set in the oil) and the temperature in the threenecked flask should reach 125°C. The steam line is then opened, water is eliminated from the water trap, and only dry steam introduced into the flask. The condensate can be collected in a flask or beaker or graduated cylinder. The temperature of the oil should be no higher than 200T and the temperature of the gum should not be allowed to eo above 140°C. The distillation is eomplete when nearly clear water condenses in the condensers.
'Roberts, R. M., Gilbert, J. C., Rodewald, L. B., and Win@we, A. S., "An Introduction to Modern Experimental Organic Chemistry," 2nd Ed., Holt, Rhinehart and Winston, Inc., New York. 1974. ZPine gum is available from a numher of companies: among them are: Stallworth Pine Products Co., P.O. Box 114. Mobile, Alabama 36601, Union Camp Corporation, P.O. BOX570, Savannah, Georgia 31402, Taylor-Lowenstein and Co., P.O. Box 1368, Mobile, Alabama 36601, FRP Company, P.O. Box 349, Baxley, Georgia 31513.
Separate the turpentine fmm water by means of a separatory funnel and measure the volume of turpentine obtained. When the turpentine distillation is completed, the steam line is opened and immediately disconnected, and the hot rosin in the flask is poured through a very small plug of glass wool in a preheated wide-necked funnel into aluminum weighing pans. The product should be a light amber color. When the bulk of the rosin is removed from the flask, pour about 50 ml of solvent into the flask
before it cools to dissolve the residual rosin. (A portion of the tur-. pentine can be used for cleaning.) Dry a t least 5 ml of the turpentine over sodium or magnesium sulfate (1-2 g estimated) for marking. Turn in properly labelled samples of rosin and dry turpentine. Give approximate % yield of both. The extra rosin can he retained by the student.
Volume 52. Number 10, Ocfober 1975 / 673
