ANALYTICAL EDITION
December, 1945
chloride-benzene were approximately 10% higher than those with n-heptane-methyl cyclohexane. This may be due to inaccuracies in the liquid-vapor equilibrium values used, though it was observed that the plate action was slightly frothier for the latter system. It appears that there is no appreciable liquid entrainment in the vapor stream, since 50- and 25-mm. plate spacings gave the same efficiencies. It may be that the increase of efficiency with increased weir height is primarily a result of the better mixing of the liquid due to its longer detention time on the plate. Oldershaw (7) obtained efficiencies comparable to column 3d with a liquid holdup similar to column la. The method of construction employed by him would be expected to give very even plate action and complete mixing of the liquid, independent of the holdup. The inserted plates, which are not perfectly horizontal and perhaps with slightly irregular perforations, were observed to be only partly active a t low distillation rates. (At speeds less than 0.2 mole per minute some of the plates employing 1-mm. wiers would run dry.) This should cause preferential liquid flow and “shorting out” of part of the plate. The effect is most pronounced in the case of the weirs permitting flow around both ends (cf. columns 3a and 3c). X comparison with Oldershaw’s column 4 ( 7 ) shows that the same efficiencies were obtained with column 3d. His liquid holdup is much better, being 0.57 to 2.23 ml. per theoretical plate com-
A
805
pared to 2.7 to 4.5. The smaller holdup used in his column enables him to use a plate spacing of 25 mm. whereas column 3d requires a minimum spacing of 30 mm. Column l a (Table 111, B) has a similar holdup but an H.E.T.P. approximately 50% greater. This could be decreased by the use of around-the-end baffles. It is estimated that approximately 16 man-hours are required by the authors to construct a complete 48-plate column (Table 111, B), exclusive of the time necessary for making the die and setting up the equipment used. Since this latter factor may be a major handicap to their use, the G. Frederick Smith Chemical Co., Columbus, Ohio, has offered to make these columns available to those interested. LITERATURE CITED
(1) Broniiley, E. C., and Quiggle, D., IND.ENG.CHEM.,25, 1136-8 (1933). (2) Bruun, J. H., IND. ENG.CHEM.,ASLL.ED.,8, 224-6 (1936). ENG.CHEM.,24,482-5 (1932). (3) Fenske, M.R., IND. (4) Grisxold, J., Ibid., 35, 247-51 (1943). ( 5 ) Griswold, J., Morris, J. W., and Van Berg, C. F., Ibid., 36, 111923 (1944). (6) Langdon, W. M., and O’Brien, G. M . , Jr., IXD.ENG.CHEM., A N ~ LED., . 16, 639-40 (1944). (7) Oldershaw, C . F., I b i d . , 13, 265-8 (1941). (8) Rosanoff, M. .4,, and Easley, C. W., J.A m . Chem. SOC., 31,953-87 (1909).
New Mercury Manometer JESSE WERNER
Process Development Department, General Aniline and Film Corp., Grasselli,
T
.
H E simplest and most generally used type of manometer for organic work is the closed-end U-type mercury manometer. However, it is somewhat difficult to fill ( 4 ) , and an even worse drawback is the fact that it must be cleaned and refilled or boiled out periodically because of the accumulation of air bubbles in the closed end ( 5 ) . Rechenberg (3) has devised a more intricate manometer of this type which overcomes these difficulties to a large extent, and Zimmerli (5, 6) has improved and modified it t o make it more practical. This latter manometer is, however, much larger than the original C-type, and consequently unwieldy. In addition, excessive quantities of mercury are needed for its operation. When desired for use in a barostat a s s e m b l y , i t cannot b e readily mounted on a small c o n t r o l p a n e l , a n d when once mounted, it must be removed regularly for tilting in order t o remove air bubbles. It was therefore considered desirable to design a mercury manometer that would be as simple and compact as the closed-end U-type and at the same time could be rid of air bubbles n ithout emptying or dismantling from a stationary setup. ilfter numerous experiments with different modifications of Zimmerli’s design (5, 6) a suitable model was arrived at. I t s construction is shown in the accompanying figure.
N.J.
The manometer is ca. 200 mm. in height and 45 mm. wide. The arms are constructed of 17-mm. Pyrex tubing and placed 6 mm. apart for easy reading on an etched-glass sliding scale mounted centrally behind them. The bottom is made from 2mm. bore capillary tubing. Height to the bottom of stopcock A is 160 mm. Both stopcocks are 2-mm. bore, vacuum-tight, and standard taper. The cup is 18 mm. high and of 13-mm. tubing. For the upper connection, 8-mm. tubing is used. The outlet is made from 2-mm. bore capillary tubing. The top of arm A is uniformly tapered down under the cock to prevent bubbles from collecting anywhere other than a t the very top. The plug of stopcock B is scored slightly on opposite ends t o prevent a mercury hammer upon opening. A small amount of Dow Corning Silicone grease is used to lubricate the stopcocks. I n order to fill themanometer, the requisite amount of pure and dry mercury is added to the unmounted manometer through the cup, with both stopcocks open. The cup is sealed by a stopper, and the manometer evacuated by means of a good pump. By warming gently, or tilting to t h e horizontal and tapping, the air bubbles are removed. Stopcock A is closed and a slow stream of air allowed to bleed into side B. The manometer is now ready for use. Should an air bubble develop a t the top of side A , the manometcr is attached t o a vacuum pump with both stopcocks closed. When a good vacuum is obtained, stopcock A is slowly opened clockn.ise and then counterclockwise. A small amount of mercury will be pulled through, and all the entrapped gas removed. In normal use, stopcock A is always kept closed. When enough mercury has accumulated above st,opcock A , it is allowed to drop into side B after releasing the vacuum above the cocks. Whe’n under atmospheric pressure, the height of the mercury in side R should be about, 20 mm. above the bend. Xormal precautions ( I , 2 ) should he taken for high-vacuum work. LITERATURE CITED
(1)
Burton, M.,ISD. EXG.CHEM.,ANAL.ED.,9, 335 (1937).
(2) Hickman, K. C . D., Rev. Sci. I n s t r u m z n t s , 5, 161-4 (1934). ( 3 ) Rechenberg, C . von, ”Einfache und fractionierte Destillation”. p. 117, Miltitz bei Leipzig, Schimmel &, Co., 1923. (4) Werner, J., ISD. ESG. CHEM.,ANAL.ED., 10, 645 (1938). (5) Ziiiinierli, A , , I b i d . , 10, 283-4 (1938). (6) I h i d . , U. S . Patent 2,075,326 (1937).
