The use of steam distillation for the iso- lation and purification of organic compounds is so wide- spread that it is routinely includcd in undergraduate instruction. Apparatus using available components and power-plant line steam has been described.' How- ever, line steam is frequently contaminated with rust inhibitors. Other methods of steam generation, i.e., using a free flame or a heating mantle, has limitations since the former is often a safety hazard and the latter docs not give smooth and rapid control of steam flow.

One of us previously describedZ a steam generator and distillation apparatus which functioned effectively in the steam distillation of small quantities of acetic acid in the ICuhn-Roth determination of C-methyl groups. Since then the design of our steam generator and the steam-distillation glassware has been modified to the current one shown in Figure 1. Thc generator supplies clean steam with sensitive control of steam flow. The simplicity and the reliability of operation of the entire apparatus as well as the ease of construction make it ideal for general laboratory use, hut it could also be considered as a substitute steam source in isolated laboratories or in small teaching laboratories which make use of heating mantles and only rarely need steam. If mounted on a portable rack, the apparatus is easily transported.

During use, the immersed heating coila is capable of operating on 140 V and heating 4 1 of water4 from 26OC to boiling at 110 V in about 17 min. During a trial steam distillation with the steam generator preheated, 13.2 g (0.1 mole) of tetralin was steam distilled a t 100 V in 25 min, a total volume of 575 ml of condensate being collected. Other Variacs settings at SO, 90, 100, 120, 130, and 140 V gave S, 12, 17 ,30 ,34 and 40 ml/min of condensate.

If the voltage is reduced so that the steam is no longer produced, the system cools and the contents of flask I , provided the steam inlet tube dips below the surface of the liquid, will be forced into trap h and possibly flask d. This may be prevented by opening the clamp g to allow equalization of the pressure.

The series of baffleplates (n in Fig. 1) serve to produce

E. J. Eisenbraun, H. Hall,

and M. W. Adkins Oklahoma State University

Stillwater, 74074

'FIESER, L. F., AND FIESER, MIRY, "Reagents for Organic Synthesis," John Wiley & Sons, New York, 1967, Vol. 1, p. 25.

A Laboratory Steam Generator

and Steam Distillation Apparatus

-

Z E ~ s ~ ~ n ~ ~ U ~ , E. J., MCELVAIN, 8. M., AND AYCOCK, B. F., J.Amer. Chem. Soe., 73,1331 (1951).

SProlongedoperation at full voltageislikely tosoften insulation on ordinary rubber-covered electrical cords and consequently a well-insulated electrical lead is recommended.

The water used for the steam generator should be free of in- organic material since salts will corrode the resistance wire and also allow electrical conduction.

Vmiac, 10-amp, Model WMT3.

eddies and thus reduce mechanical entrainment of non- volatile components from flask 1. That entrainment is minimal was demonstrated by carrying out a blank steam distillation u-ith 5 g of I<hln04 and 250 ml H20 charged to flask I (1 1 flask). Colored droplets m r r splashed to the first baffleplate hut did not appear he- yond this point. Any splashover of nonvolatile matc- rial during distillation usually results because flask 1 is too small for the amount being steam distilled or be- cause excess water has been allowed to accumulate in flask 1. A larger flask vill correct this difficulty.

f I-SCALE 2

O&

S C A L E - I N C H E S

Steam dirtillation apporatur.

Thermometer, adopter, 3 24/25, Kontes K-179800. Copper or bra., rod, 0.25 X 6-in. threoded at both ends and fined a t each end with two brass nut,. The electrical cord leading from the Voriac to the brorr support rods should withstand 110 V AC. An 18-gauge, 2-strand, arbestos- covered cord wor used. Flask. round-bottom. 5 I. center neck b 45 /50 and 3ide necks T . . 24/40, Konter K-60600: Heating element, Nichrome, 12-omp, Master Appliance HAS-01 8K. Copper wire leodr, 16-gouge. Droin tube and pinch clomp. Condensate ond back-flow trap with 3 45/50 ioint. Steam inlet tube. 6 24/40, Konter K-179000. Still heod fined with o 3 24/40 ioint ot top, 0 7 50130 boll joint a t bottom, on O-ring ioint, clamp-sire 65/40, Corning 6 7 8 0 in the middle and a 5 35 /20 boll iaint a t the condenser end. clamp, 7 50/ i0 . ' Flosk, round-bottom, q 50130.

~ ~

Heating mantle. The Teflon baffle train consisting of four ~erforoted, 4-mm thick X 40.mm diameter Teflon dater connected bv a 5-mm diameter Teflon rod. Clamp, 7 65/40. Clamp, 7 35/25. Conden3er, Grohom, with o 7 35/25 rocket, 400-mm length.

Volume 49, Number 6, June 7972 / 441

The O-ring joint of j permits dismantling to clean the While we have not experienced a need for a relief baffle train. Earlier models using permanently fixed valve, a mercury relief valve could be installed as a T glass baffleplates were considerably more difficult to connection to the condensate trap h. build and were more fragile. We thank our Research Foundation for partial sup-

The still head j also is useful for many laboratory port and Dr. 0. C. Dermer for having read the manu- distillations. script.

442 / lourno1 of Chemical Education