V O L U M E 2 1 , NO. 5, M A Y 1 9 4 9
637
in the design and construction of this apparatus, and Leonard J. Druker of the Visking Corporation for his numerous tests of the design under laboratory conditions.
apparatus. Using the falling film method described here, compounds such as stearoyl chloride and sebacyl chloride have been rapidly distilled to give clear water-white products at 1 to 5 mm.
LITERATURE CITED ACKNOWLEDGMENT
The author gratefully acknowledges the aid of H. S. Martin of the H. S. Martin Glass Company, Evanston, Ill., for assistance
(1) Quackenbush, F. W., and Steenhock, Harry, IND.ENG. CHEM., ANAL.ED.,15, 468 (1943). R~~~~~~~J~~~ 6,194s.
Vacuum-Jacketed Vapor Dividing Reflux Head W. R. DOTY California Research Corporation, Richmond, Calif.
HE advantages of the vapor dividing head over the more T c o m o n liquid dividinghead have beensummarieed by Collins and Lante ( 1 ) as follows: 1. There is less product leakage at total reflux. 2. The moving partrts are more accessible. 3. The reflux ratios are closer t o the "off-on" ratio of the timer. 4. There is no leakage of reflux to take off during flooding.
In the commercially available head (Glass Engineering Labo- . ratories, Belmont, Calif.) described by Collins and Lantz these advantages are compromised by the fact that the single solenoid operated valve in its ''product-on" position closes the throat of the reflux condenser. As s result of this construction the valve
traps some liquid in the condenser and when the valve changes t o the "product-off" position some of this liquid is transferred t o the product line. I n operation a t high reflux ratios this characteristic causes a reduction in the reflux ratio. The head described below overcomes the above difficulties by employing two separate single-acting valves, one of which closes the reflux condenser while the other opens the product line and vice versa. The liquid reflux, therefore, never comes in contact with the product take-off valve and only saturated vapor passes the latter. The condenser is integral with the head, and access to the valves is provided through two 14/35 standard-taper ground joints. As these are not exposed to appreciable quantities of liquid, they cause no trouble due to sticking or leaking.
TOP VlEH
GLASS VACUUM JACt ilAPOR DIVIDIN(
1 /r N-
'E VIEW
U
re
mamma raper valve sleeve removable for regrinding. redaoing, or cIs&ing valve
D. Bulge to sumort solenoid
E. F. G. H. I.
Prodnot take-off line Thermometer m pyrometer point well Refiux valve detail Reflux aondenser Liquid s e d to allow reflux run-hack while valve LS
dosed
SCALE IN
INCHES
c1 O
FRONT VIEW
re Beat, finely ground L..
-
FIGURE I.
I
E
Vacuum=nd/orlight vapor trLke-off Preseuree quaiisingline with reUux oondenser for oondenilation of light prod uot "spore L. T o atandard deaign produi;t coder and cut taker 8:od/or receiver M. Tubulatia8nS for Silvering &"C I evsouating N. Standard tawr to fit datillal;ion ColUmn P . Erpansioin bellows R . ReRurvab e seat, finely ground J. R.
Figure 2
ANALYTICAL CHEMISTRY
638 In this design 8. liquid-sealed reflux return line ( I , Figure 1 ) by-passes the reflux valve. This prevents the valve from t r a p ping liquid in the reflux condenser and so smooths out the operation of the column and tends to minimize flooding. Figure 1 gives elevations, tap view, and details of the head. Operation. The head has been operated -with a variety of cypes of columns and under pressures varying from atmospheric to a few millimeters. It is equally satisfactory for either pressure condition, although its mechanical advantages are pitrticularly noticeable under vacuum. 'Under atmospheric pressure its maximum capacity without flooding is about 3600 ml. per hour. When i t does flood, it is a t the base of the reflux valve. The throughput can be increased at the expense of a slightly larger holdup by increasing the diameter of the liquid seal (I,Figure 1) in the reflux line. The valves are operated by either alternating or direct current adenoids, which, in turn, are actuated by t~ timer. The timer
must be arranged so that it simultaneously cuts one solenoid into the circuit as the other is out out. Both mechanical and electronic timers have been used and units have been fabricated which pennit the adjustment of the reflux ratio with a single dial. Ratios varying from 1:l to 1OO:l are easily obtainable and the actual reflux ratios are very close t o the "off-on" ratios of the timer. The head and its accessories are readily adapted to multiple setups and as many as six stills have been operated in a battery by one man. Figure 2 shows the finished vapor dividing head unsilvered. LITERATURE CITED
(1) Collins, F. C., and Lantu,
V.,IND. ENO.CHEM..AN\,..
fin. 18
673 (1946). R n c r r r m J u n ~24. 1048
Small laboratory Centrifugal Molecular Still R. M. BIEHLER, K. C. D. HICKMAN, AND E. S. PERRY Distillation Products, Inc., Rochester, N . Y .
efficient, quantitative molecular disAREQUIREMENT , . . that thefordistilland tillation shall be exposed in a thin film
CYCLIC BATCH CENTRIFUGAL . ~ O L E C U L A KSTILL
IS
with uniformity of area, thickness, and rate of feed. This has been done in various ways, the most promising of which at present is the use of s heated centrifugal cone for spreading a distilland supplied a t constant rate.
with modiccd contour. From the disprammstio elevation in
east-aluminum rotary evaporator, which contain? an embeddd
4
DISTILLATE
t
FEED
Figure 1. Centrifugal Molecular Still of C:yolio B a t c h Type The simplest, complete distillation unit embodying this arrangement is a cyclic batch still with double reservoir (Z). Figure 1 shows this to comprise a still head, two reservoirs, a circulating pump, and a manifold for attaching a vaouum system. There are necessarily many campoqent parts and constructional pieces in making a versatile unit of this kind. The problem in designing a small centrifugal still suitable for laboratory bench use IS to diminish the number of parts without sacrificing the functions. The progress that has been made to date in meeting these requirements is described in this paper. In Figure 2 is shown a :nodel of the complete still unit.
F i g u r e 2.
Five-Inch Centrifugal Molecular Still
