An Economical Continuous Distilling Apparatus FRANK M. SCHERTZ, 1305 Farragut St., N. W., Washington, D. C.
DETAIL OF VALVE
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HE recovery of large quantities of solvents in isolating carotene, chlorophyll, and xanthophyll led to the development of the distilling apparatus illustrated. It was economical of heat and practically eliminated all danger of fire. !rhe storage bottle which contained the solvents to be distilled was elevated high enough so that gravity alone caused the liquids to flow into the distilling flask, after passing
through a condenser which was used as a preheater. The storage bottle could be placed a t a distance from the still and thus reduce the fire hazard. The flow of solvent into the distilling flask was controlled by means of an automatic float (3.5 X 6 om.) which kept it a t a constant level during distillation. The end of the glass rod (5 mm. x 5 cm.) which was part of the valve was ground into the modified inlet tube, so that a seal was made when the liquid in the distilling flask caused the float to rise. The parts were constructed as illustrated, so that they would not stick. Holes were made in the top of the cage (4 x 8 cm.) of the valve so that the air would not be trapped and prevent the float from rising. The 3-liter distilling flask contained an inverted U-shaped small-bore (2-mm.) glass tube to eliminate bumping as well as a glass tube extending to the bottom of the flask through which waste liquors could be siphoned off. The oil bath was made of copper, silver-soldered a t the seams. Nujol or any oil with a high flash point may be used in the bath. In recovering methanol or acetone from an aqueous solution the temperature of the bath often ran as high as 170" C. Using a 1000-watt hot plate of the open type with a threeheat switch control, 2.5 liters of 95 per cent ethanol were distilled in 1 hour. Solvents with boiling points between 20" and 100" may be easily distilled or recovered.
Acknowledgments Indebtedness is due Carl Rist for suggesting the use of a float for maintaining the constant level of the liquid in the distilling flask, Arthur Mack for its construction, and Mrs. Constance Sherry for the drawing. RECBIIYED June 29, 1935.
An Automatic Still Cut-Off ARTHUR H. HALE
AND
the magnetic switch is held in contact through one of its own arms, a momentary interruption of the current will open it. To close the magnetic switch, the momentary switch is connected across the 220 gap in the magnet v o -\ t-s_ _ _. c i r c u i t and only by p u s h i n g this switch can t h e s t i l l c i r c u i t be completed once it is o p e n e d . This circuit is applicable for use with any e l e c t r i c a l l y operated machine which m u s t not o p er a t e beyond a certain time limit a n d w h i c h must n o t again operate after the FIGURE 1. WIRINGDIAGRAM 12-hour interval of A . Magnetic switches the clock. P. Fuse (110 volt)
FRED D. TUER'IMLER
T. Jefferson Coolidge, Jr., Memorial Laboratory, Harvard University, Cambridge, Mass.
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SIMPLE fool-proof automatic switch for breaking the circuit to an electrically heated Barnstead conductivity water still was needed to prevent any possibility of burning out the heating units by boiling the still dry. Either an outside or inside float switch seemed impractical, since positive action might not always be certain in alkaline permanganate from which the water was distilled. By calibrating the rate of distillation on the glass level indicator in terms of the drop in the water level in &minute intervals, it was possible to use a time-clock switch to operate a magnetic switch controlling the still. However, if the magnet was controlled only by the clock switch, the still would turn on automatically a t 12-hour intervals, or if the current stopped even momentarily, the clock would stop until started again manually but the still circuit would be closed again when the current returned without any possibility of being opened by the clock. In either case there was no protection against burning out the heating units. To solve this problem the circuit in Figure 1 was used, the important feature of which is the momentary switch. Since
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Pilot light
M . Magnet S.
RECEIVEDSeptember 21, 1935.
441
Momentary switch T. Time-clock switch U: Manual cut-off switch (ordinarily left closed)
Carbon Dioxide from Dry Ice WALTER S. IDE Burroughs Wellcorne and Company, U. S. A., Experimental Research Laboratories, Tuckahoe, N. Y.
T HAS been found that carbon dioxide gas, generated Ifactory from the solid in convenient apparatus, is a very satissource of carbon dioxide for use in the determination a
of nitrogen by the micro-Dumas method. Carbon dioxide snow is now becoming readily available in most laboratories, 'The solid carbon dioxide in small pellets is placed in the mercury trap, which is a test tube 20 mm. in diameter and 20 cm. long, fused t o another tube of like dimensions (Figure I). The open end of the tube is fitted with a stopper containing a stopcock. A few minutes after introduction of the pellets the air in the trap will all be expelled. By closing stopcock A , the gas will be forced into the 8- t o 10-liter aspirator bottle which has been filled with freshly boiled water and may be graduated to measure the quantity used. The water is forced out through s ecial nitrometer tubing into a large thick-walled rubber bladder (feavy beach ball). On setting up the apparatus, it is convenient to flush the aspirator bottle and bladder with carbon dioxide from a tank, filling the bladder with water before connecting to the bottle. The water will then flow into the bottle until it is filled and the bladder is deflated, ready to receive the carbon dioxide as it is generated. The bladder should be placed on a shelf approximately level with the top of the aspirator bottle. This height should be adjusted so that there will be positive internal pressure at all times. The carbon dioxide should be released and replaced several times. This will insure very small microbubbles in the azo-
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FIGURE1
tometer; in fact, the bubbles obtained appear to be smaller than those obtained by any other source. After some weeks the size of the bubbles increases very slightly. It is good practice to refill the generator about once each week during routine work to eliminate the possibility of this error. The method was suggested by J. S. Buck of this laboratory. RECEIVEDAugust 7, 1935.
Stirring Air within Desiccators FRANK J. ZINK, Kansas Agricultural Experiment Station, Manhattan, Kan.
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find it useful in similar applications. Small fans mounted on pivots inside the desiccator were induced to rotate by a series of mechanically moved permanent magnets passing near the outside of the desiccator. The equipment was used in a series of investigations of equilibria moistures of forage hays and grains, in which 15 desiccators, each with enclosed fan, were used. Figures 1, 2, and 3 illustrate the apparatus, the cost of which, exclusive of motor, was approximately $15. Many laboratories already have most of the apparatus available. Metal desiccator plates were substituted for the usual porcelain plates. Small pivots were made, as illustrated in Figure 2, of steel wire about 0.0625 inch in diameter and 3 inches long and were soldered t o the edges of the plates. The upper end was bent in such a manner as to offset it toward the center of the plate, so that the entire area of the plate would be free for moisture dishes. The ends of the pivots were sharpened t o a point.
NUMBER of investigators have used sulfuric acid solutions as a means of humidity coatrol within small enclosed spaces. Wilson (2) suggested the use of desiccators for humidity chambers in conjunction with equilibria moisture determinations and pointed out the desirability of keeping the enclosed air in motion. However, Wilson ( 2 ) and Wilson and Fuva (3) did not use desiccators in their many equilibrium moisture determinations, possibly because the stagnant air resulted in a low rate of interchange of moisture. Lindsay (1) also pointed out the undesirability of such determinations in stagnant atmospheres. Obviously, any mechanical means of stirring air within desiceators would be difficult to arrange and might interfere with the normal convenient use of the desiccator. The author has evolved a simple means of stirring air within desiccators, and presents it with the hope that others may
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FIGURE1
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