fixed-speed, gear-head motor with a shaft speed of approximately 0.5 r.p.m. and theability to exert 36 inch-pounds of torque a t this speed. The rotating disk was driven at this same speed and the agitator a t only a very slightly higher speed. By using a fixed-speed motor, the rate of delivery could be adjusted by changing the gear ratio to the disk or by constructing disks having different numbers and sizes of holes. I n practice, the latter method was found more expedient. Obvieusly, it is possible to obtain widely different delivery rates by this method. Into the exit port in the aluminum plate there was tight1 threaded a piece of aluminum pipe, 1 inch in diameter, 0.126 incg i n wall thickness, and 1 inch long. Suitable connection was made from here to the pyrolysis tube.
Device for Introduction of Solid Reagents. Harry M. Andcrscn and Robert P. Zelinski, De Paul University, Chicago, Ill. N A
series of pyrolysis experiments recently carrictl out in this
I laboratory it was necessary to introduce a solid ch:trge at a slow, eonst:int rate into a tube furnace for periods up to 8 hours. This was accomplished with the device described here.
As shown in Figures 1and 2, the apparatus consisted essentially of an aluminuni hopper, under which was located a slowly rotatinch thick and 5 inches in ing, horizontal aluminum disk, diameter, with a ring of 40 holes of 0.189-inch diameter around its edge. This disk rested on a fixed, circular, aluminum platc, 0.25 inch thick and 6 inches in diameter, and was (.overed by :I Lucite plate, 0.28 inch thick and 6 inches in diameter, to whioh the hopper was secured by means of a bronze flange. The Lui;itc and aluminum plates, between which the disk rotated, were separated from each other by slightly more than the disk's thickness by means of a spacing ring and gasket paper. They were sturdily fastened around their circumference with machine screws tapped into the aluminum plate. The perforated aluminurn disk was rotated by means of :t 0.25-inch brass shaft passing through a rubber-sealed bcaring in the lower aluminum plate. As the ring of small holes in the disk passed under the hopper, the holes were filled with the solid niaterial contained therein; after rotating 90" the holes passed over an exit port ill the lower aluminum plate. This exit port connected directly with the upper end of the vertical pyrolysis tube. In order to prevent bridging of the solid in the hopper and consequent failure of the material to fill the holes in the disk, it \vas necessary to insert a simple, slowly rotating agitator in the hopper. This-agitator was supported by a rubber-scaled bearing in the Lucite cever of the hopper. Gasket papcr \vas used between all the parts of the assembly to effect seals. As shown in the diagram, genrs and shafts NYIY fitted to both the rotating disk and the hoppw :tgitntor, so that both csould be driveii f i v i i i :i ronimon souri'i\. Thc pon.(?r soiir(.e w:ts R small.
_i! 1
IS"
6" DIA.
'I
Figure 2.
f
\-IF/
3/16' COPPER NITROQEN INLET
Top View of Rotating Disk Assembly with Hopper Removed
The specifications in the drawings are those for the disk actually used in most of the experiments here, which delivered approximatcly 0.5 gram per minute of d typical organic compound, a t a rate constant to within 1%. The delivery rate will vary with the density and granular size of the solid. Using a disk having sni:tller holes, and reducing the speed of the disk by changing the gem ratio, feed rates as low as 0.040 gram per minute and constant to within 1% were achieved.
I
0"
ALUMINUM HOPPER
T o overcome the tendency of the material to stick in holes rather than fall out the exit port, the undersides of the holes were slightly beveled, and directly over the exit port a solenoid and cylindrical iron slug were mounted. The solenoid was activated by a pulse of current seventy times a minute, so that the slug was repeatedly lifted and allowed to fall upon a bolt in the Lucite plate. The slight jarring resulting therefrom caused the material to drop from each hole as it passed over the exit port. The pulse of current was derived from an electronic timer originally d e s i y d to operate the solenoid valve of a partial takeoff still head w ich happened to be available. Any simple repeating switch, such as that used for operating blinking display signs, should be suitable. With a more freely flowing material than that used, both the hopper agitator and the vibrating device might be unnecessary.
I UBBER SEAL 7/O'PIlCH DIA. BEVELBEARS
Figure 1.
n
I
Apparatus for Introducing Solids into Furnace
Tho entire assembly was so mounted that it could be conveni1
1461
ANALYTICAL CHEMISTRY
1462 ently removed from the motor and weighed before and after a run to determine the amount of material charged. Aluminum and Lucite were favored in the construction to reduce the tare weight. THISwork w ~ l lperformed with the aid of U. 8. Navy funds under Subcontract 1, Contract NOrd 10431, a prime contract with the Hercules Powder Company, Allegany Ballistics Laboratory.
Versatile Laboratory Concentration Device. L. C. Craig, J. D. Gregory, and Werner Hausmann, Rockefeller Institute for Medical Research, New York, N. Y.
I
N BOTH chromatography and countercurrent distribution the
problem of rapid quantitative recovery of solute from relatively large volumes of dilute solution is encountered. The apparatus shown schematically in the diagram overcomes many of the difficulties.
II
The solution to be concentrated is placed in a round-bottomed flask, A . B is a bulb which is at least as large as or larger than A and has an inlet tube C, whose width and opening are not smaller than the standard taper connecting A and C . The other opening in B is a 7-mm. glass tube which is located opposite and in line with C. The smaller opening is connected by a short piece of rubber. tubing, D, to a 7-mm. glass tube approximately 15 cm. in length which has a standard ball joint (2/5), E , at its further end. The other part, F, of the joint is held stationary by a clamp attached to a ring stand and connects to the vacuum pump through a rubber tube. The glass tube which connects D and E passes through a cork borer, G , which is supported by a clamp attached to the ring stand to serve as a bearing. The tube also passes through a rubber stopper which is forced into a hole in the center of the wooden pulley, H, and thus is made to grip the tube tightly. The pulley is turned by a leather belt and a smaller pulley attached to an electric motor which has a reduction gear (20 to 1 ratio) and an appropriate slidewire resistor. Flask A and bulb B are supported by two small wheels with solid rubber tires. For operation, joint E is well greased with a heavy stopcock lubricant and evacuation is begun. The motor is then started and the speed is so adjusted that the steady rotation of A and B does not greatly disturb the surface of the liquids in either vessel. B serves as the condenser. It may be cooled by the ice and water contained in the flat pan, I. Ice is added to the pan and the maximum surface of B is cooled because it is rotating constantly. Heat a t any desired temperature is supplied to A by water in Dan J. Because A rotates steadily, a film of the liquid is constantly being pulled up on the upper inside wall and a relatively large heated surface is thereby furnished for vaporization. Thus distillation takes place rapidly without ebullition as in molecular distillation pickman, K. C. D., Znd. Eng. Chem., 29,968 (1937)l and there ia little or no tendency for bumping when pressure and temperature are properly adjusted. Even salt solutions have often been quietly brought to dryness. The familiar capillary leak or boiling stone ia completely unnecessary. For solutes of poor stability, the level of the warm water in J can be reduced
as the solution in A decreases; thus, overheating of the dry residue is avoided. Moreover, if evaporation a t a low temperature is desired, dry’ice and acetone can be placed in I and a high vacuum can be with an Oil pump. The apparatus then a Convenient freeze-dry assembly. Device for Filtering Solutions into Reagent Bottles. C. W. Fleetwood, North Dakota Agricultural College, Fargo, N. D. procedures for the preparation of standard potassium S permanganate 2) state that the solution is to be filtered into the reagent bottle. Filtering of most mixtures without the OME
(1,
aid of suction or pressure is a waste of time, yet no suggestion is given to aid in following the procedures. If the mouths of reagent bottles were large, or if all laboratories were equipped with bell jars large enough to cover bottles of various sizes, the precess would be simple. Thought waa given to the construction of a simple, inexpensive device which would be applicable. .. The filter device illustrated was constructed of borosilicate glass tubing, a borosilicate glass crucible with fritted disk, and two rubber stoppers. A fritted disk may be used instead of the sintered- lass crucible. This size of apparatus may be used for filtering solutions into reagent bottles with mouth openings of 1 to 5 cm. Changing the dimensions of various parts will give devices of different sizes and capacities. The principles employed by Rothman ( 8 ) may be used to construct a filter device for filtering into reagent bottles, but such a device would be more susceptible to breakage than the one illustrated. The device is attached to a suction line containing a 3-way stopcock which can be used as a vent to stop filtration, and to isolate the system from the pump while venting it. The lower stopper is set on the reagent bottle and a t the same time the tube leading to the solution to be filtered is placed in the solution to the required depth. The suction line is opened by closing the vent on the stopcock and pressure on the bottom stopper seals the glass-to-rubber junction. The formation of a vacuum within the system causes the solution to feed automatically. Once filtering has begun, the system requires no sttentiol,, providing there is no possible backup of water from the vacuum line trap. Filtering may be s t o p p e d b y venting the vacuum line or by placing both hands on the shoulder of the bottle and pushing with the thumbs on the bottom stopper. I n filtering mixtures which contain suspended precipitates that clog or are difficult to remove from the filter plate, the plate should be covered with an asbestos mat. To prevent contamination of the solution by the top rubber stopper, a ground-glass joint construction can be used a t that point. The device has been in use in this laboratory for 2 years and has been a very practical time saver in filtering large volumes of reagents, as well as in filtering potassium permanganate into reagent bottles. LITERATURE CITED
(1) Fales. H. A., a n d Kenny, F., “Inorganic &uantitstive AnslySis.” New York, D. Appleton-Century Co., 1939. (2) Griffin, C. W . , “Inorganic Quantitative Analysis,” p. 188, PhiLadelphia, Blakiston Co., 1949. (3) Rothman, S.,ANAL.CHEM.,22, 367 (1950).
