Carbon Dioxide from Dry Ice WALTER S. IDE Burroughs Wellcorne and Company, U. S. A., Experimental Research Laboratories, Tuckahoe, N. Y.
IT
HAS been found that carbon dioxide gas, generated from the solid in a convenient apparatus, is a very satisfactory source of carbon dioxide for use in the determination 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.
A
NUMBER of investigators have used sulfuric acid
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.
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
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.
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FIGURE1
442
NOVEMBER 15, 1935
ANALYTICAL EDITION
/7GNEr ,,-CIRCULAR
FAN
(t
Pwor
TABLE
I
FIGURE3
Sheet-metal tin disks 2.5 inches in diameter were cut and punched at the center with an ordinary center punch, care being used not to puncture the metal, to serve as the socket of a pivot bearing. Six radial cuts 1 inch deep were made in the edge with tin shears, and the segments were bent to serve as fan blades. These fans were then balanced on the pivots and the unit was placed inside the desiccator, so that the fans when in place just cleared the side. The fan may be lifted off the pivot and laid aside for removal or insertion of the sample dishes. With this type of pivot the fans rotated freely and were induced to rotate by magnets passing near the outside of t,he desiccator and on a level with
44 3
the fan. The electromagnetic flux permeating the glass induced the fan to rotate, and no mechanical connection to the fan was necessary. The motive Dower was furnished bv a series of motor car magneto-magnets mounted on a circular platform, on a Boston Gear Company show window display unit of 48 to 1 ratio. An 1800-r. p. m., 0.125-h. p. electric motor was belted directly to the gear unit. A 2.5-foot diameter platform furnished ample space for 15 desiccators placed in a circle concentric with the platform and just outside the circle created by the passage of the magnets. The magnets were passed at the rate of 8 feet per minute and the more freely moving fans rotated at approximately 200 revolutions per minute.
Literature Cited (1) Lindsay, D. C., International Critical Tables, Vol. 2, pp. 321-6 (1927). (2) Wilson, R. E., J. IND. EXG.CHEM.,13, 326-31 (1921). (3) Wilson, R. E., and Fuva, T., Ibid., 14, 913-18 (1922). RECEIVED September 17, 1935. Agricultural Engineering.
Contribution No. 66, Department of
A Molecular Still WILLIAM H. STRAIN A N D WILLARD M. ALLEN The University of Rochester, School of Medicine and Dentistry, Rochester, N. Y .
I
N THE course of the purification of the corpus luteum
hormone, progestin (S), it was found necessary to subject the highly purified concentrate to distillation in a molecular still. Since the described devices designed for use with small quantities were not entirely satisfactory for this purpose, a new type of apparatus modeled after the molecular still of
Yl
cated it was annealed and the surfaces ground for highvacuum work. The still was heated by means of a small oil bath placed around the well of the apparatus. I n operation the thick oil to be distilled is dissolved in a small amount of ether and transferred by pipet to the well, The solvent is removed by cautious warming or by an air jet and the last traces by evacuation-hst with a water pump and then with an oil pump. During this preliminary evacuation the condensing part of the apparatus is not used, the upper end being closed with a rubber stopper. Finally, when it is apparent that easily volatile substances have been removed, the stopper is replaced by the condenser, and the apparatus, including the trap, is attached to the intake of a mercury vapor pump. With the joints well greased and the mercury pump trapped with solid carbon dioxide, a vacuum of 0.0002 mm. is attained in a very short time, providing no distillation is taking place. By slowly heating the oil bath surrounding the well the distilling temperature is reached without any visible boiling and a waxy substance soon collects on the pestle from which it can be removed by immersion in benzene or other suitable solvent. A well of the size used will accommodate from 1 to 2 grams without difficulty. The detailed set-up of the high-vacuum apparatus and the technic of operation were essentially those described by Hickman and Sanford ( 2 ) . This same apparatus has been used for the purification of a, number of other products of biological origin and appears to be adapted to a large variety of conditions.
Literature Cited
FIGURE1
Carothers and Hill (1) was designed. The still has the advantage that, in addition to being readily charged and cleaned, the temperature of distillation may be simply controlled. The still (Figure 1) was constructed from tm-o pieces of oldstyle, flanged Pyrex pipe, 15 X 5 cm., the final dimensions being given in the diagram. After the apparatus was fabri-
Carothers, W. H., and Hili, J. W., J .
Am. Chera. Soc., 54, 1557 (1932). (2) Hickman, K. C. D., and Sanford, C. R., J. Phys. Chem., 37, 637 (1930). (3) Wintersteiner, O., and Allen, W. M.,J . BioT. Chem., 107, 321 (1934).
(1)
RECEIVED August 29, 193.5.
