ANALYTICAL CHEMISTRY
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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).
