A
Variable Pressure Manostat
HUGH B. D O N A H O E , ROBERT R. RUSSELL, C A L V I N A. VANDERWERF University of Kansas, Lawrence, Kan.
Improved Adsorption Vessel ROBERT B. A N D E R S O N Central Experiment Station, Bureau of Mines, Pittsburgh, Pa
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T IS often convenient and sometimes necessary to reproduce or vary the pressure on a given system. The diagram shows an arrangement by which pressures may readily be set at any desired value or varied continuously, between limits determined by the efficiency of the pump and the height of the manostat, without removing the manostat from the vacuum line or interrupting the progress of the distillation. iMost vacuum distillations are conducted within the range from 1 to 250 mm. Any pressure within this range can easily be obtained by using a regulator of the Newman type (1)and inserting into the system a reservoir of mercury. Use of ethyl phthalate limits the range but makes possible more delicate setting. The height, H , of the liquid in the manostat can be changed manually during a distillation merely by adjustment of the reservoir (see diagram). A stopcock placed below the reservoir may be used to assure a constant head after setting. The entire assembly can be blown to order, but it is possible to make a very creditable model from a drying column. Pressures above 250 mm. can be obtained by placing in series with the manostat described above two ordinary Newman regulators filled to the 250-mm. level. If the stopcocks are set so that both these regulators are by-passed, the range will be as stated above. With one tube cut in the range will be 250 to 500 mm.; with both, 500 to 750 mm.
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N THE study of metal-oxide catalysts such as used in the Fischer-Tropsch process by low-temperature adsorption isotherms, it is desirable to reduce the catalyat in the adsorption vessel and to determine the weight loss upon reduction. "he adsorption vessel shown in Figure 1 has proved convenient in such studies. It is small and light enough to be weighed in an analytical balance. The absorption vessel consists of a catalyst chamber and a special four-way stopcock. The bores of the stopcock plug are arranged so that both are open in the position shown, while a t an angle of 180' from this position pnly the right bore is open. The stopcock plug is of hollow blown construction, and the diameters of bores and capillary tubing are 2 mm. The catalyst chamber is made just large enough to accommodate the sample required, usually 1 to 2 cc. The catalyst chamber is provided with a tube for charging and a thermocouple well. Figure I The tubes leading to the stopcock contain loosely packed wads of glass wool to prevent the catalyst from blowing out of the chamber. The adsorption vessel is connected T to the adsorption or reduction systems by a 10/30 capillary .~ ground-glass joint. With the four-wav stoocock the samde can be connected to the system for adsor-ption'or evacuationwith one bore open, and with both bores open a stream of hydrogen can be passed over the catalysts. The sample of catalyst usually is weighed in the adsorption vessel before the charge tube is sealed. After sealing all weighings are performed with the vessel evacuated. Fresh samples are evacuated for an hour a t 125" C. to remove water and other vapors that are held physically. The catalyst chamber is placed in a furnace in a horizontal position to avoid heating the stopcock.
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Usually nitrogen adsorption isotherms a t 195" C. were determined on the sample before and after reduction, and in some instances several isotherms were run during the course of reduction. With this adsorption vessel it also will be possible to study the effects of treatment of the catalyst with gases other than hydrogen, such as synthesis gas or carbon monoxide, on the surface area and pore structure, and to determine the weight loss of the adsorbent upon evacuation.
A. To pump 8. To syatem I n the authors' opinion such a n apparatus provides a more inexpensive and convenient method for checking boiling points a t the pressures recorded in the literature than any heretofore described. The manostat has proved especially useful in the fractional distillation of mixtures when it is advantageous to distill the various components under successively lower pres-
ACKNOWLEDGMENT
sures.
Acknowledgment is made to Martin Michael for preparation of the drawing. The special stopcock wm made by Eck & Krebs. LITERATURE CITED
PWBLIEHED by permisaion of the Director, Bureau of Mines, U. 9. Depsrtment of the Interior.
(1) Newman, M. S., IND.ENQ.CHEM.,ANAL.ED.,12, 274 (1940).
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