1426
ANALYTICAL CHEMISTRY
single-pole, double-throw switch of relay R-3 closes, cutting off the power to the stepping relay and to the thermal delay relays. Simultaneously the clock starts. If this cycle is not completed by the end of 10 seconds, the safety delay relay, 0 - 2 , opens and the main power relay, R-I, opens, shutting down the machine. At the end of a preset interval (2 to 55 minutes) the clock opens its switch, Sw-5,relay R-3 reverses its sm-itch,Sw-4,and the stepping relay moves the distributing arm one position. The delay relay c l o ~ after e 5 seconds and the cycle continues. These cycles are repeated until the distributing arm trips the mercury switch, Sw-3, which cuts off the power to the entire unit. The pump ceases and the column flow is stopped by the solenoid valve.
ess. 4 s the power to carry out the change of receivers is supplied by a weight, and it is desirable t o use as little power in the controlling mechanism as possible, the receivers for the fractions are kept stationary, and receivers are changed by moving a rotary distributing arm by means of an indeying mechankm a n d a solenoid-controlled escapement.
ACKXOWLEgCYENT
The authors wish to thank E. D. Schall for his help in the design of the electrical circuit LITERATURE CITED (1) Boggs, L. il., Cuendet, L. S.,Dubois,
AI., and Smith, F., ;\SAL.
('HEM., 24, 1148 (1952). (2) Brimley, R. C., and Snow, A , , J . Sci. Instr., 26, 73 (1949). (3) Carlander, -4.T.. and Gardell, S.,Arkiz Kemi,4 , 32 (1952). (4) Cuckow, F. W., Harriss, R. J. C., and Speed, F., J . SOC.CRem. I d . , 68, 208 (1949). (5) Durso, D. F.. Schall, E. D.. and Whistler, R. L., . ~ N . I L . CHEM., 23, 425 (1951). ( G ) Dustin, 3. I?., Ind. chim. belg., 17, 255 (1952). (7) Fitch, F. T., and Russell, D. S., As.41,. CHEM.,23, 1469 (1951). (8) Gilson, A. R . , Chemistrg & I m h s t r g , 10, 185 (1951). (9) Grant, R. A., and Stitch, 8. R., I M . , 1951, 230. (10) Harris. J. O., Ibid., 1951, 225. (11) Hough, L., Jones, J. K. X., and Wadman, W.H., J . Chem. Sac., 1949, 2511. (12) James, A. T., AIart,in,A. 5 . P., and Randall, S. S., Biochem. J . , 49, 293 (1951). (13) LIader, C., and Mader, G., Jr., h . 4 ~ CHEM., . 25, 1423 (1953). j14) Phillips, D. M. P., S n t u r e , 164, 545 (1949). (15) Randall, S. S.,and Xartin, A. J. P., Biochem. J . Proc., 4 4 , ii (1949). (16) Rienian, W.,and Litidenbaum, S., . h . i L . CHEX, 24, 1199 (1 952). (17) Stein, W , H., and Noore, S.J., J . Biol. Chem., 176, 337 (1948). (18) Thompson, -4.,and Wolfrom, h l . L., J . Am. Chem. Soc., 73, 5849 (1951). (19) Whistler, R. L., and Durso, D. F., Ibid., 74, 5140 (1952). (20) Whistler, R . L., and Tu, C. C., Ibid.,74, 4334 (1952). (21) Wolfrom, M. L., Georges, L. W.,Thompson, A., and Miller, I. L., Ibid., 71, 2873 (1949). JOURNAL
Paper
663,
Purdue r n i v e r a i t y Agricultural Experiment
Station.
Figure 1
The fraction collector proper is shown in Figure 1. The largest part of the indexing mechanism is the disk, A , into which are driven, a t equal intervals, the 36 pins, B (small finish nails). The rod, LV,revolves in the bearing, J (a piece of sheet metal, adjustable over a large hole in the deck of the apparatm), and a bottom bearing, not shown) which consists of a nail driven up through the base of the m a c l n e and engaging a hole drilled in the lower end of S. The escapement, C , is actuated by the solenoid, S; both of these are mounted on base E , which is adjustable with regard to A and B. Drum F is attached t o -1-by means of a setscrew; and strin G, wound on F , passes over pulleys HI and Hz to weight I,whkf is attached to G by means of a clothespin. The upper end of S carries a clamp, K , which in turn carries distributor arm L, which dischargpq into vials .If (ordinary specimen vials, with pour-outs made in the laboratory), which are set on predetermined mutually tangent circles, so that the indesing of the distributor arm is accurate.
Simple and Inexpensive Fraction Collector. R.J. \Iirigo a n d Iben Browning', Departments of Biochemistry and Biolog? The University of Texas, M. D. Anderson Hospital for Cancmw Research, Houston, Tex.
.
investigators have published designs for devices tha S"automatically fractionate the effluent from chromatographic 1
VERAL
columns, distillation units, etc. ( 1 - 4 ) . Schroeder and Cory (3) list references to fiimilar machines; several devices of this type are available commercially. The commercial devices are rather expensive, and the construction of the others is usually a machineshop operation, A need exists, therefore, for a simple automatic fraction collector which can be constructed cheaply from readily available materials, and made without recourse to machine tool work. The design presented here adequately fulfills the first criterion; and although a metal-cutting handsaw, drill press, and power grinder mere used in the actual construction of the apparatus, its construction with ordinary hand tools should be feasible. This fraction collector is a flow-time type-that is, the effluent of, say, a chromatographic column, is fractionated by changing receivers a t equal time intervals. T h e interval can be changed during a run without serious effect on the accuracy of the proc1
Present address, American Optical Co., Buffalo, N . Y.
f
c
Figure 2
V O L U M E 2 5 , N O , 9, S E P T E M B E R 1 9 5 3 Thc action of the escapement, together r i t h construction principle?, i p shown in Figure 2.
As in Figure 1, A is the disk, with pins, B, and C is tho fork of the escapement.. Pallet 1 of C must be filed or ground to present an a r c of a circle centered on screw Q to B; pallet 2 of C is less critical, but should he cut so a8 to engage B when the solenoid, S, is energized. S is wound on a glass tube, bent to form an arc of a circle centered on Q (armature P is also bent on this arc). 0 is soft iron, and ~ e r v to e ~complete the magnet,ic circuit.. R is stop pins to limit the movement of C. C, 0, and S are mounted bv means of vooden blocks on a wooden
to A , so that pallet 1 of C @events rotation of A &en the salenoid is inactive, and pallet 2 of C checks A on actuation of the solenoid and also restores pallet 1 of C to position upon deactivation of the coil. Weight I (Figure 1 ) and the voltage supplied to the solenoid are adiusted to eive reliable oneration. The authors' solenoid is wouid nzith KO. 26 enameled copper wire, and has a resistance of 34 ohms. When a weight of 94 grams is used,
The current supplied to the solenoid for actuation of eseapement is controlled by the timer shown in Figure 3. The timer is driven by a small rvnchronous motor, A , turning
1427 but it should be easy to increase the c;lpacit,y with only .z slight, increase in size of the escapement. LITERATURE CITED
(1) Baggs, L. A., Cuendet. L. S.. DuBois. M., and Smit! CHEM.,24, 1148 (1952). ( 2 ) James, A. T.,Martin, A. J. P.. and Randall, S. S., YYICIIIIII. .,., 49, 293 (1951). (3) Schroeder, W. A., and Core?. R. B., AXAL.CHEW..23, 1723 (1951). (4) Stein, W. H., and Moore. S.. J . Bid. Chem.. 176, 337 (1948).
Photoelectric Volume-Measuring Accessory. Herbert J. Dutton and Francis d. Castle, Nort.hern Regional Roscxreh Laboratory, Peoria 5, Ill. are frequent occasions when fractions of specified T"" volume between 5 and 20 ml. need to be collected auto,RE
matically. In many instances of chromatography, distillation and liquid-liquid extraction rates of flow may vary too greatly to permit the use of " t i m 4 o w " mechanisms or may he too rapid for drop-counting mechanisms. The following apparatus may be assembled from parts readily available or constructed in most, laboratories. A "plug-in" method of connecting this From Column
1
The weighi of t,be 'glass fram&ork, axlei and &heel provides enough friction far the disk to drive the wheel. Wire E, cementid to the d e , turns mith it, and the two ends of E pass, once per revolution, through the mercury cups, F , dosing a circuit to actuate a relav IH-B relav Tvoe SS-5). modified to operate normally open).' -The relapin "(urn co&ols the current into % variable transformer, which supplies the solenoid.
6
A slightly modified timer of this sort has been operated reliably using a cheap spring-driven alarm clock to turn the disk. It should therefore be possible, by using direct current from storage batteries to operat,e the escapement, t o conduct fractionations completely independent of the ordinary building u t i l i t i e e which is a point of importance in regions vhere electrical supply is unreliable.
Figure 3
A schematic repmsmtntion of this aceesso~yis given in Figure 1.
This fraction collector and timer was built a t a cost for parts (other than the relay and veriable transformer) of less than $10. Using only hand tools, a duplicate could he built by one person in between 2 and 3 days; if power tools for cutting the disks and the iron parts of the escapement mechanism were available, this time could be considerably reduced. The device has performed well and reliably, mainly for isolations. It should be readily adaptable to analytioal operations, as, a t the flow rates used, very little material is lost in drops while the distributor arm is moving from one receiver to another. The simplicity and cheapness of the appaxatus should recommend it to the smaller laboratory, or for isolation procedures generally. I t s only drawback a t present appear8 to be its limited endurance-it would operate only 6 hours without attention if 10-minute fractions were collected-
A is a.light mume; B , a slit; and C, a photoelectric relay. A Fisher-Serfass photoelecbrie relay and a Worner Products relay have been used successfully. In general, photoelectric relays of high light sensitivity are preferable because they permit more leeway for narrowing the light beam, far using lower intensity light sources, et,c. D is a normally closed singlep$e, single-throw relay; E a normally open double-pale, smgle-throw relay; and F, 8. Christmas tree blinker. A button type which fits into a light socket was used, rated for 60 watts. G is a solenoid coil from a 110-volt mercury relay or solenoid valve, and H is a 60-watt light bulb. The glass float, I, is blaun to have thin walls and is silvered internally before sealing off. The reservoir, J , is constructed from a borosilicate glass 25-ml. Mohr pipet. At its lower end is ground a surface to seat a steel ball bearing, K . This surface is.ground with the aid of silicon carbide and a hall bearing of t,he size of K , welded to B steel rod and rotat.ed in a Inthe.
