June 15, 1942
ANALYTICAL EDITION
112
two major fractions were, respectively, a-pinene and dipentene. The small middle fraction on analysis was found to be p-menthane, which the temperature plot fails t,o detect. Figure 5 gives curves for the separation of a mixture of terpene alcohols a t 20-mm. pressure. Prior to distillation this mixture had a relative viscosity of 31. The operation of the column for a material of this viscosity is nearly as easy as it is for a mixture whose relative viscosity is much less, such as a- and /3-pinenes. This ease of operation with such viscous materials makes the spiral screen type of column particularly valuable in the analysis of many terpene mixtures.
I07
Conclusions
I5000
127
+ 1.4900
122
vj p\I
a
CL
n
117
r
t
P w
X w
L 1.4800
3 +
2 a x
W
z
I4700
&
1.4600
0
10
20
30
40
50
60
ML.DISTILLED FIGURE5 , FRACTIOSATION OF TERPESE ALCOHOLS AT 20 h h . 0 Refractive index @
50s
Temperature
For these distillations a total condensation-partial take-off head was used, as illustrated in Figure 3. The advantages of this modification are its large condensing surface, compactness, and strength. C o ~ u 5. ~ a As a preliminary test this column was used to separate a mixture of 35 ml. of carbon tetrachloride and 35 ml. of cyclohexane into approximately 90 mole per cent carbon tetrachloride and 100 mole per cent cyclohexane. The holdup of the column under the conditions of operation was 13 ml. and the separation required 36 hours. When fractionating terpenes, column 5 was so regulated that the head reflux was about 0.8 ml. per minute. A head reflux ratio of 25 to 1 was used on the plateaus of the distillation curves but usually a higher ratio of about 40 to 1 was used when passing between plateaus. The low pressure drop of this column combined with its high capacity minimizes any thermal reaction b y allowing an analysis to be completed in a short period of time. I n Figure 1 is included a separation of a-pinene from /3pinene made with this column. Figure 4 gives curves for the separation of a mixture of apinene and a dipentene cut of commercial material. The
For a loose packing the 4 X 4 mm. Berl saddles perforni well with terpene materials. Columns with the spiral screen packing are the most economical and efficiently operative columns for terpene fractionations yet reported.
Acknowledgment The authors wish to express their gratitude to B. J. Otte, curator of the Chemistry Department, for his efforts in obtaining materials, to Fred Hayes, the machinist, who was so helpful in working out the details of punching and fitting the screen spirals, and to P. J. Thompson, the glassblower, who constructed the glass apparatus.
Literature Cited (1) Beatty and Calingaert, IND.ENG.CHEM.,26, 504, 904 (19341. (2) Bromiley and Quiggle, Ibid., 25, 1136 (1933). ESG. CHEM.,ASAL.ED.,12, 544 (1940). (3) Lecky and Ewell, IND. (4) ,Morton, A. A., "Laboratory Technique in Organic Chemistry", 1st ed., p. 80, New York, McGraw-Hill Book Co., 1938. ( 5 ) Peters and Baker, IND.ENG.CHEM.,18, 69 (1926). (6) Selker, Burk, and Lankelma, IND. ESG. CHEM.,AXAL. ED., 12, 352 (1940). (7) Tongberg, Quiggle, and Fenske, IND. ESG. CHEM.,26, 1213 (1934). (8) Ward, U. 9. Bur. .Mines, Tech. Paper 600 (1939). (9) Whitmore. Fenske, Quiggle, Bernstein, Carney, Lawroski, Popkin, Wagner. Wheeler, and Whitaker, J . Am. Chem. SOC..62, 795 (1940).
A Trap to Prevent Backflow from Suction Pumps ARTHUR E. JIEYER, Research Laboratories, hlaltine Company, New York, N. Y.
T
HE backing up of water from suction pumps whenever there is a decrease in water pressure in the supply line is a n annoyance known to every chemist. Small metal balls placed in the side tube of the pump are efficient only if the pressure drop is sudden, causing the water to shoot back with a jerk. A gradual drop will permit the water to pass slowly over the ball without moving it, and thus the aperture of the tube will not be closed. M o s t commonly used is a glass trap of the type illustrated. The ground-glass ball, A , rests on the aperture of the tube that leads to the apparatus to be evacuated, and is pressed down by the air at any reduction of the efficiency of the pump. Since this doe-. not give an absolutely air-tight seal, watcr
slowly backs up into the trap and only when the ground surface is wet is a perfect seal obtained. If the pressure in the water supply returns, the trap contains water through which the air stream must be sucked, causing a corresponding decrease in the vacuum obtainable. Even without water in the trap, the weight of the glass ball must be subtracted from the maximal vacuum obtainable. This trap can easily be changed into a very satisfactory device by using a hollow glass ball that is lighter than water. In this case the trap is reversed in the position, leaving the connections as indicated by the arrow. The ball rests normally on three indentations in the middle of the trap, where sufficient space is left for the air to pass around. If the water backs up, the ball is lifted from its resting position and pressed against the upper tube outlet, sealing it tightly. With return of the suction, the water ia automatically removed from the trap and the ball returns to its previous position. This trap works reliably and gives satisfactory results. I n case of sudden release of pressure, the ball will be lifted by the air stream and so close the upper tube without the aid of mater. I t thus holds a partial vacuum for a considerable time, even when dry. The trap with the floating ball has been made by the Scientific Glass Apparatus Company, Bloomfield, S . J.
