tetrachloride is more difficult to handle in such minute volumes. Best results were obtained by placing a n excess of a precooled carbon tetrachloride solution in the area of the sample loop, thus using 0.1 to 0.2 pl. of solution. The main advantage of the above techniques is their relative simplicity. An additional advantage lies in the ease of locating and focusing on the samples, which had a larger cross section than that of the infrared beam at its focus point. Hoivever, because the thickness of the samples is not accurately reproducible, these methods are suitable only for qualitative measurements. The sample volumes required are small; approximately 0.02 111. of liquid by Method A and about 0.08 pl. of solution by Method B. The relative ease of handling tends to compensate for the larger 1-olumes that are required here as compared to the silver chloride capillary method.
control the f l o ~rate with fluctuations not exceeding 3% for periods up to 16 hours, and it should be simple in design and easy to fabricate in the laboratory. Satisfactory control of flow rate was not obtained by either a glass stopcock or a Teflon micro needle valve.
-CHROMATOGRAPHIC COLUMN
@f -10/30
ST JOINT
FLOW R E G U L A T O R
POWDERED PYREX G I.ASS (40-60MESH)
ACKNOWLEDGMENT
The authors are indebted to D . R. A . JT‘harton and hl. L. K h a r t o n for their helpful suggestions and to L. 11. Dogliotti for the photograph. LITERATURE CITED
Blout, E. R., “?\licrospectroscopv,” vol. I, part 111, 2nd ed., p. 2179, “Technique of Organic Chemistry,” ed. by .4. Weissberger, Interscience, New York, 1951. Blout, E. R., Parrish, JI., Jr., Bird, G. R.. -4bbate. 11. J.. J . Ont. SOC. Amer.’52, 966 (1952). Coates, V. J., Offner, h.,Siegler, E. H., Zbid., 43, 984 (1953). Davison, W. H. T., Ibid., 45, 227 (1955). Friedel, R. h.,Pelipetz, AI. G., Z b i d , 43. 1051 11953). Perk& Elmer Znstrument X e u s 5 , S o . 3, 8 (1954). Sager, T. P., ISD.ENG.CHERT., AXAL. ED.4, 388 (1932).
Device for Regulating Small Flow Rates in Chromatographic Columns L. H. Gevantman, R. K. Main, and L. M. Bryant, U. S. Naval Radiological Defense Laboratory, San Francisco 24, Calif.
of investigations involving column chromatography of true solutions, a device was needed to moderate the flow rate of eluate to approximately 3 or 4 ml. per hour. The following additional characteristics were desired: The device should be easily adjustable to columns of different inherent initial flow rates: it should
I
N THE COURSE
170
ANALYTICAL CHEMISTRY
GLASS WOOL
A satisfactory all-glass device consisted of a tube 6 em. long and 3 mm. in inside diameter, constricted a t the bottom and fused to a female 10i30 standard-taper joint a t the top. This tube was filled with fluid and packed n-itli powdered Pyrex glass (Corning Glass Co. KO.7740, 40- or 60-mesh glass ponder) to a desired height. A plug of glass wool a t the constriction fixed the powdered glass in place. This column was fitted to a male standard-taper joint which was connected through a stopcock to the bottom of the chromatographic column proper. T h e flow rate through the resulting flow regulator n-as adjusted by suitable changes in column diameter and length and in grain size of the powdered glass. Within limits, the facility with which the height of the powdered glass may be adjusted in the tube provides a flexibility hitherto not obtainable from a suitable capillary tube. Furthermore, excessive lengths of capillary tubes are not needed in this compact device.
Fraction Cutter for large Scale Column Chromatography Julian E. Philip and Jay R. Schenck, Abbott Laboratories, North Chicago, 111.
efficient fraction cutter for scale chromatographic columns has been used in this laboratory for over a year. This all-glass unit is especially useful for collecting fractions of 0.5 to 20 liters. SIMPLE,
A large
A complete unit is shown in Figure 1. Tubing 10 ml. in outside diameter is used, except for the 15-mm. portion which contains the float. The top surface of the float is ground against its seat to provide an efficient shutoff. Three or four indentations are made below the float, so that solutions may flow rapidly down the tube. These units are connected in series by tubing to the chromatographic column During operation, the effluent from the chromatographic column flows through the T-tube and down around the float into the container. ’IThen the liquid level in the container reaches the bottom of the straight glass tube, the solution rises in this tube and in the T-tube until the float seats and further f l o ~is diverted to the next unit. This effectively prevents mixing during the column operation. Before disassembly. the tubing is disconnected from the column and gently blon-n out with air. This removes the solution from the horizontal part of the T-tubes and the connecting tubing. The principal source of contamination of early fractions by later fractions is the volume above the float This solution enters the container nhen the stopper is removed at the end of the experiment. I t is, therefore, desirable to make this part of the T-tube as short as possible.
ti K L I N D E N T A T I O N
Figure 1.
Fraction cutting unit
The amount collected in any container is determined by the position of the bottom of the straight glass tube or T-tube (whichever is higher) and may be thereby adjusted. The top of the straight glass tube must extend above the T-tube enough to allow a considerable head of liquid if many units are used. ACKNOWLEDGMENT
Thanks are due Chester Swopes for constructing the first units.
