fit and staked against the lover side of the table shaft shoulder. The bole left in the lower end of the shaft by the center drill and counter sink serves as a lon-er bearing surface which rides on a 0.25-inch hardened steel ball placed in the bottom of the bushing. The turntable consists of a disk of 0.5-inch plywood, 22 inches in diameter, center drilled 0.376 inch. To facilitate placing the inch depressions spaced equally on a receivers, sixty 1 X circle of 913/16-inchradius with respect to the center are cut in the table with a Forstner bit. The table rests on a support plate and is secured by a 3/s-inch nut The table is turned by a r.p.h., 2.5-watt synchronous timing motor (Hayden Mfg. Co., Torrington, Conn.) mounted on a bracket attached to the base block. A 64-tooth gear is used as the driving gear. This arrangement results in one complete revolution of the table every 15 hours, or four receivers passing a given point per hour. As the turntable is moving continuously, it is necessary to prevent loss of eluant between receivers by using the flexible dropping tip (Figure 3) in conjunction with the positioningr.p.m. timing disk. The disk is mounted on the shaft of a synchronous motor (Hayden Mfg. Co., Torrington, Conn.) supported by a suitable bracket and rotates in the opposite direction to the rotation of the tahle.
Automatic Fraction Collector for Column Chromatography. Oliver G. Lien, Jr., Elbert A. Peterson, and David M. Greenherg, University of California, School of Medicine, Berkeley, Calif. and Moore have developed methods for the chromatographic separation of amino acids on columns of starch Chem., 176, 337 (1948)l and an ion exchange resin [Cold Spring Harbor Symposia, Quant. Bid., 14, 179 (1950)l. These are excellent for investigating the interconversions occurring when ClA-labeled amino acids are administered to the intact animal or are incubated in tissue preparations used in biological Rork. Several fraction collectors for use in conjunction with column chronia?'5: tographyareavailablecommercially, ----. .-3/e' Thread particularly the elegant one designed by Moore and Stein, but none is readily adaptable to the collecting of fractions directly in counting planN i D Shoulder chets which can be assayed for radio' activity after the solvent has been 2 Strolgbt Parallel Knurl evaporated. This is of prime importance in survej ing the distribution 3 of radioactivity in a given system. To obtain maximum separation of Combinol on the radioactive components, a simple r~ Center Dr 1 1 and inmpensive f i action collector %as - 373 Counter S n h de-igned, in M hich the samples are collected and dried in the counting Figure I planchets. TEIN
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No. 6 Machine Screw De Khotinsky Material
Description of Collector. The collector consists of a continuously rotating table, a flexible capillary dropping device for attachment to the end of the chromatographic column, and a rotating sector disk (positioning-timing disk), which positions the capillary tip over the receivers and defines the time of delivery to each receiver.
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P0SIT;ON I NG-TIMI NG DISK
CAPILLARY DROPPING ASSEMBLY
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Figure 3
Operation of Collector. The arrangement of oomponents is shown in Figure 2. The disk is placed about 0.5 inch higher than the collector table, and the column with the dropping capillary attached is placed in such a position that the follower of the capillary dropping assembly has a point (about 0.125 inch above its tip) in common with the circle described by the groove in the disk. The disk as it rotates acts as a cam with which the follower of the capillary dropping assembly is alternately engaged and disengaged, giving rise to two positions of the dropping capillary, the "engaged position" and the "free position," separated horizontally by a distance equal t o about one half the diameter of a receiver The magnitude of the distance is best adjusted by raising or lo\Tering the column. For best operation the line of travel of the dropping capillary should be perpendicular to and across the line joining the center of the turntable and the center of the disk. To follow a cycle of operation, assume that the follower has just disengaged from the groove and is in the free position. The table has been adjusted by manually rotating the table assembly, so that the capillary tip is above a point of the receiver midway between the center and leading edge of that receiver. During the first 180" of rotation of the disk the table rotates clockwise a distance equal to one half the dinmeter of a receiver. The
Lapiiiary uropping Assembly
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Synchronous Motor 1/15 R O W
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Figure 2
TABLE AW,EXBLY. A closed brass bushing, drilled and reamed 0.375 X 1.75 inches, is sunk in the main block of the wooden base. This bushing receives the table shaft (Figure l), machined from cold-rolled steel, which carries the driven gear and table ~upp01-tplate (Figure 2). The table support plate, which rests upon the upper surface of the table shaft shoulder, is a 2 X 0.5 inch washer with a 0.375-inch hole (sliding fit over upper end of the table shaft). The driven gear, a 32-pitch, 40-tooth l/16inch flat b r a s spur gear, drilled and reamed 0.375 inch, is force920
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immediately prior t o disengagement of the follower from the groove, the reaeiver has moved another one-half diameter. As the follower disengages from the groove, the resulting movement a i the capillary tip carries it across the gap between the receivers and to the starting position over the second cup. Theabiriples are dried by a 412-watt Iar showcase p (General : t r i c 40T8) backed with an aluminum ioil reflector (Figures 2 and 4). At about 0.5 irkh above the eamples this wi!l remove approximately 1.5 ml. of 1.5 M hvdrochloric acid- in 2.5 hours. Whencorrosive solvents such as hvdrochloric acid" are eva orated, a s m d l u c i t e hood connected t o a vacuum system
the fumes. The actual distance of displacement of the capill a w tin can varv from distanoe Figure 4 just sufficient to bridge the ap between two a4aceht receivers t o almost the distance equal to the internal diameter of t.he receiver, and still function properly. The drop of solvent OD the capillary tip at the time the follower disengages from the groove will be thrown into the new receiver when the table is properly adjusted. The receivers itre usually 1-inoh diameter polyethylene counting planchets (Formold Plastic Co., 3141 South Wabash Ave., Chicago, Ill.). However, a table on which 17 X 50 mm. shell vials are used as receivers, was made by gluing two disks of 0.75inch plywood together and drilling 5 / ~ X I>/, inch holes adjacent inch depressions. The table size was scaled inst+ of 1 x aocordmgly. The smaller diameter of the receiver makes adjustment for operation difficult and a vial of larger diameter is recommended. This fraction collector has been used in conjunction with an ion exchange resin (Dowex 50,250/5M)-mesh) for separating the compounds present in the protein-free filtrate obtained from the incubat.ion of radioactive amino acids in preparations of rat liver.
indicator DaDer). The =mole. in a minimal volum& is then i n t k duced an-the top of the cOl& and the collection of fractions started. The rate of flow of solvent through the column can he adjusted either by a pressure regulator or by raising or lowering t h e reservoir. The assembly, including the fraction colleetor, column, a flow meter, and the reservoir is shown in Figure 4. The pressure regulator (mercury type) is not shown. The bubbletype flow meter incorporated in the feed line b e tween the reservoir and column consists of the graduated section of a 0.2-ml. Mohr pipet, a T-connection, and a small Nbber bulb. , T h e rate of flow can alm he measured by counting drops with a stopwatch, but this is less convenient than use of the flow meter. The T-tube is mounted in a vertical plane with two openings in the vertical axis. The pipet fits inside the horizontal arm and its opening is a t the junction of the T. The reservoir connection
is to the lower opening of the T and the bulb used t o inject an air bubble into the pipet is attached to the upper opening. Flow rate can he measured by determining the time required by a small bubble t o travel the calibrated distance of the pipet,
As the time interval of collection of each fraction is accurately defined, the uniformity of the fractions will deDend uDon the uniformity of the rate of flow of the eluant through the column. For the authors' purpose the assembly described gave sufficiently uniform samples. However, variations in Ron rate due to fluctuations in room temperature and changes in eluant composition were noted. This problem can he eliminated by the use of B constant feed device. Although the fraction collector was constructed to collect fractions in counting planchets and has been used only with columns in which Dowex-50 has been used a6 an adsorbent, it should be useful for nonradioactive separations and with columns of other adsorhents. A longer or shorter period of collection of fractions can be obtained by proper choice ai the motors, which are available in a wide variety of shaft speeds. A ~ E by D research grant9 from the Liie Insurance Medical Reeearoh Fund and the Hobson Fund, Canoer Research Institute, University of Callfornia School of Medioi
Apparatus for stances for stitute of Baking Laboratories, Chicago, Ill.
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officisl method of the Association of Official Agricultural TChemists . . for determining ash in SiNpS, sugars, beverages, HE '
jellies, and similar food products consists of evaporating the water a t 100"C., adding a few drops of olive oil, and further heating over a low flame until swelling ceases. If suliated ash is desired, sulfuric acid may be added to the sample prior to evaporation and charring (2,S). Difficulty is encountered in these determine tions, as the liquids frequently tend to foam with resulting loss of sample. I n addition, during the initial stages of charring these materials, especially those high in carbohydrates, tend t o swell with iurther chance for loss of sample. Thus the method requires close attention during evaporation and charring, or the process must be carried out at I O N temperatures with resulting loss of time. These difficulties may be minimized or entirely avoided if heat is applied to the top rather than the bottom surface during the evaporation and charring process.
pans 5 inihiiin diameter and 0.75 inch in decth are attached ti the underside of the metal plate to reflect and somewhat concentrate the heat downward. Ring gas burners supported by the back legs of the stand are placed below the aluminum pans. The evaporating dishes oontaining the sample to he preashrd are held on support rings &ached to the front legs of the pre-asher. ~
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by the aluminum pan: The heat may bk regulated by transformer.
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vari'ahle
By using this apparatus the evaporation and charring can be carried out rapidly, frequently requiring as little as 15 minutes, with no danger of undue foaming or excessive swelling. Furthermore, no smoke or odors are scattered in the room, as the volatile materials are completely burned. After the tendency t o swell has ceased, the sample is transferred to 8 mufflefurnace and the ashing is completed a t recom mended temperatures. . , ^2 to . ..., , , Solids and Sirups. Weign 13 grams of matemi mto %area 100-ml. silica or other convenient dishes. Place the dishes in the
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Present address. American Store Bakeries. Philadelphia 31, Pa.
