AIDS FOR THE ANALYST Continuous-Feed, All-Glass Rotating Evaporator Paul Kohn, Department of Biological Chemistry, University of Illinois College of Medicine,Chicago, Ill. RECEXT
article by T‘olk
[ASAL. CHEX 27, 1207 (1955)l
A describing an all-glass rotating evaporator has prompted
this report on a similar apparatus which has been in use in this author’s laboratory for some months. The apparatus described operates on the same essential principle as Yolk’s-rotation about a semiball joint-but it has the advantage of being a continuousfeed device and is much easier and much less expensive to construct.
which the chuck has been removed and replaced with a pulley. ~ ~ serve to rotate the flask with ease. Motors of 1/60 and even 1 / 1 hp. This is made possible by the use of a rather small semiball joint. Small motors were inadequate when tried with an adapter having semiball 35/20 joints, although the very expensive lubricant prescribed by Yolk m-as not tried. An ordinary 0.25-inch rubber band is used as the belt. The rubber band should be easy to stretch, rather than stiff. The position of the motor above the flask is adjusted so that some tension is pulled on the rubber band. One rubber band has been used for several days before breaking, I n addition to ease of assembly from inexpensive equipment, the parts can readily be diverted to other laboratory uses if desired. Efficiency appears to be as great as that of similar commercial evaporators, which cost a great deal more and cannot be used for other purposes. The all-glass construction of this apparatus permits its use with solutions containing hydrochloric, formic, or other volatile acids. The stainless steel, bronze, and other metallic parts of commercial evaporators preclude their use with solutions of this nature. ACKNOWLEDG!WENTS
The author gratefully acknowledges the helpful suggestions of Edv-ard E. Smissman. This apparatus n-as constructed during work on, and from funds allocated for, a project supported (in part) by research grant A425 from the Xational Institute of Arthritis and Metabolic Diseases, Yational Institutes of Health, U.S. Public Health Service.
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Modification of Beckman DK-1 Spectrophotometer for Use as a Recording Spectrofluorometer Chalmers 1. Gemmill, Department of Phormacology, School of Medicine, University of Virginia, Charlottesville, Va.
Figure 1. Diagram of continuous-feed, allglass rotating evaporator
The apparatus is assembled from ordinary laboratory equipment, as shosn in Figure 1. The entire apparatus is supported from two ring stands (not shonn in the figure). One stand supports the motor and holds an extension clamp which serves a.s a bushing around the neck of the flask. The second stand holds the adapter and separatory funnel. A round-bottomed flask with a 24/40 standard-taper neck is fitted nith an adapter having an 18/9 semiball outer joint. A short length of 0.75-inch rubber tubing is placed around the shoulder of the adapter to provide a surface with higher friction. It may be necessary to select the adapter, choosing one which has as wide a shoulder as possible. This provides a greater length on which the “belt” can operate, making it easier to adjust the position of the motor. The vacuum is drairn through an angle-type vacuum adapter, having suitable ground-glass joints as shown. I n this laboratory, the vacuum is routinely drawn through a 200-mm. \Test condenser using a water aspirator. About 300 nil. of an aqueous solution can be concentrated in an hour a t low temperature. Obviously a dry ice-acetone trap and an oil vacuum pump could be substituted, with the expectation that the rate of evaporation would be increased. Any ordinary laboratory stopcock lubricant can be used on the rotating semiball joint. Dow-Corning silicone stopcock grease is usually employed. The flask is loosely supported by an extension clamp from which the asbestos or rubber covering has been removed. K h e n the apparatus is assembled, the neck of the flask and the adapters must be in a nearly straight line and the jams of the clamp must be parallel to the neck of the flask. It is not necessary to lubricate the neck of the flask [flasks supplied by a t least one manufacturer (Scientific Glass Apparatus Co., Inc., Bloomfield, S. J.) have two ridges around the neck and these rotate in the clamp with a minimum of contact]. The motor used is an ordinary laboratory stirring motor from
VHOUGH there have been several descriptions of modifications (e,4-7) of the Beckman DU spectrophotometer for use as a
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spectrofluorometer, no description has appeared for a similar modification of the Beckman DK spectrophotometer for recording the fluorescent spectra. The modifications of the Beckman DU are designed either to place the fluorescence source in place of the light source or to reverse the optical path so that the light fiom the fluorescent source passes through the monochrometer and emerges from the loiver slit. This light is then reflected into the photocell by the plane mirror on the mounting block. APPARATUS
It was decided to use the first method for the modification of the Beckman DK-1. The lamp from a back plate was removed, and a hole was bored into the back plate in such a position that when light passed through the hole it excited fluorescence in the sample which occupied the former position of the lamp. The fluorescent light of the sample was picked up by the mirror mounted in its usual position on the back plate and passed into the spectrophotometer. I n this manner, none of the exciting light reached the aperture of the spectrophotometer. A wooden block vias placed in the bottom of the lamp housing Ivith a groove cut in the top in order to poPition the cell. Two methods viere used to isolate the wave lengths for excitation. I n the first method a Coining filter 9863 was placed over the hole in the back plate in order to cut off wave lengths over 410 mp. A 1.50-watt Hanovia xenon lamp (10-C-1) vas used as a source. I t was placed in a housing n i t h the arc 9 cm. alvay from the filter. The second method involved the use of a Bausch & Lomb monochromator. The light was passed through the monochromator, which was set a t a predetermined ivave length. The emergent light from the monochromator passed directly onto the sample. Large rectangular cells, 2l/8 X 2.25 X 9/16 inch in outer diameter (manufactured by Klett), were used except for wave 1061
