A N A L Y T I C A L CHEMISTRY
836 Table I.
Volume of Pycnometers at 0' C.
Pycnometer 1, MI.
Pycnometer 2, MI.
39.97 30.95 39.94 30.95
36.15 36.13 36.15 36.14
Av.
results summarized in Table I1 give a comparison of the densities obtained by this method with those Obtained by other means. No corrections were made for buoyancy, because most of the results reported are accurate to within 0.001. However, a simple buoyancy correction has been suggested by Lipkin el al. (6) where the correction is C = 0.0012 X (1 - determined density). This works only where the pycnometer has been calibrated with water as recommended here.
Table 11. Densities of Pure Liquids at 0' C. Pycnometer Pycnometer
Compound CFrCIz
1
2
1.402 1.399 1.401" 1.287 1.622
1.401 1.401 1.39ga 1.286 1.621
Other Workers 1.395 ( 2 )
LITERATURE CITED
(1) Benning, A. F., and MoHarness, R. R.,
I d . Eng. Chem., 32,
814 (1940).
(2) Bichowsky, F.R.,and Gilkey, W. K., Ibid., 23,366 (1931). (3) Eilarts, K.,Smith, R. B., and Cook, A. B., U. 5. Bur. Mines, RepLlnvest. 3474 (1939). (4) Goodhue, L. D.,and Haaen, A. C., ANAL. CAEM., 19, 248 (1947). (5) Hovorka, F.,and Geiger, F. E., J . Am. Chem. Soc., 55, 4759 Run on refractionated material. (1933). (6) Lipkin, M. R.,Mills, I. W., Martin, C. C., and Harvey, W. T., ANAL.CHEM.,21,504(1949). (7) Looke, E. G., Brode. W. R., and Henne, A. L., J . Am. Chem. DENSITIES OF PURE LIQUIDS Soc., 56, 1726 (1934). (8) Reidel, L., 2.ges. K d l t e - I d . , 45, 221 (1938). Density determinations were made on dichlorodifluoromethane, (9) Swarts, F.,J . chim. phys., 28, 622 (1931). difluoromonochloromethane, and 1,1,2-t~rifluoro-1,2,2-trichloro- (10) Walden, C. H., University of Colorado, unpublished work. CHClFt CCIFI-CCI1F
1 . 2 8 6 (calcd.) ( I ) 1 . 6 2 1 2 (calcd.) ( f ) 1,6210 ( 8 ) 1 , 6 2 0 0 (7,9) 1 . 6 1 9 5 (6)
ethane, using the same procedure as used in the calibration. The
RECEIVED June 27, 1949.
Method for Facilitating Recording, Filing, and lntercomparison of Infrared Spectra 0. D. SHREVE AND M. R. HEETHER Philadelphia Laboratory, E . I . d u Pont de Nemours & Company, Inc., Philadelphia, Pa. T H E large recorder traces, obtained in the qualitative scanning of infrared spectra, are inconvenient to file, difficultly accessible after filing, and cumbersome to handle when simultaneous intercomparison of several records is desired. In the caae of a Beckman IR-2 infrared spectrophotometer, these disadvantages may be and operator minimized by the following procedure, which should be readily adaptable to other instruments. The marker switch, which marks the record a t intervals correspondin to each 30" of arc on the calibrated wave-length dial, is replace! with an ordinary tapping key. Using a mechanical
automatic slit drive to close the slits at an approRriate rate, the
~~~?~~?
a recorder chart s eed of 30 inches per hour, a 26-inch record is obtained. The S i t shaft is driven by the idler shaft Of the wave-length drive by means of a sprocket wheel and ladder chain ~i~~~ 1 shows the tvDe trace ob- - of bsckmound tained dvith ti& device. Records of convenient filing size and with a ermanent wavelength scale attached are then obtained aa folgws. With the instrument dark (shutter closed) t i e 1 5 to 2micron range is scanned exactly &s described above and the
Figure 1. Sample Record Mounted on Keysort Card for Filing 1.
2.
Atmospheric background Background with dry nitrogen passing through opectmmster
/-
I
II
2%;t i
& ~ ! n ~ t ~ ~ ~ ~% :r:af$::: ~ ' to 2-micron redonis then means of the tapping key. The scanned a t a slower rate (28.5 minutes) without attent>ion. With
V O L U M E 22. NO. 6, J U N E 1 9 5 0
837
mark on the scale with that an the reoord and nhotostatically
in more favorable regions. The reduced records (Figure 1) are mounted on 8.5 X 15 inch Kevsort cards (McBee Comuanv. Athens. Ohio) and
trmnspar&t Plexiglas and the top, bottom and one side are hinged t o permit dropping of cards after insertion of needles through the appropriate parallel slots a t front and back.
Figure 2.
Sorting Box for Keyeort Cards
taouine key is taDDed every 0.04 micron-i.e.. as evew other ediibra%on*mark bh the w&e-length dial cr&s the hairline. (Marking a t 0.OZ-micron intervals results in poor delmeation in some sueetrsl reeions.) When the calibration marks have
permsnently lttaohed t,o each reobrd by aligning the 15-micron
If adequate photostating service is av&il.ilable, the entire prooedure soon becomes a routine stsndmd practice which greatly enhanoes the utility of itn ever-increasing infrared library in day-to-day analytical work. ACKNOWLEDGMENT
The simple slit drive arrangement now in use was first suggested to the authors by W. C. Kenyon, Experimental Station, Hercules Powder Company, Wilmington, Del. R e c m v ~ nMay 10, 1949.
Improved Centrifuge Type of Ultrafiltration Apparatus ISAAC FELDMAN: ROBERT A. DANLEY, AND JOHN F. O'LEARY ,University of Rochester, 1 schooz H E first use of centrifugal farce to obtain ultrrtfiltration presTmre was described by de W w d (7) in 1918. A much improved technique was described by Rehberg (6),but the author's previous experience indicated that the membrane 8UppOlt of metal would probably introduce adsorption errors. In addition, specially made cellophane tubes were required. I n B previous ultrafiltration study ( 1 ) of beryllium solutions of very low concentrations, quantitative interpretations were impossible because of adsorption losses on the sppsrhtus employed. An improved npparatus of the centrifugation type has been devised which gives excellent reproducibility and an a b d u t e 817011 of about 6% and embodies the separate advantages of those previously described (2, 4, 6, 7). The new apparatus is of all-glass construction and employs the readily mailsble Visking seamless cellophane tubing as the inembrane
SEALED WRH SCOTCH TAPE
FRlTTEO DISK.
(bl CELLOPHANE BAG USED AS MEMBRANE
ppit t
APPARAWS
The upper part of the apparatus, shown in F i p e La, wm made by sealing the ball part of an 18/9 ball-and-socket p i n t ta a co8rse porosity, borasilicrtte glass fritted sealing tube, 25 mm. in diameter. The socket art of the joint connected to B bulb of about 4 ~ 1 1 1 .rapacity wwid n~ the rcGiver for ultraliltratr. A rellophanc b3g, k"Igure 1,b. mudc by tymgdouble knots in the ends oi B u m c of \ k k i w wamleSi rrlloohmc dialyzing tubing, I9
Figure 1. Apparatus
shown in Figure 1 c To keep eonts&inrtting dust out of the apparatus during t.he centrifugation, the top of the ultrafilter wm covered with a piece of cellophane and sealed thereto with Scotch ta e Sootoh ta e and fabric-covered wire were used to seal the bafjoint. The uptrafilter was wrapped withasheet of 0.125-inch (O.%cm.)spongerubber to make it fit snugly in the metal centrifuge tube. In an International centrifuge, size 2, eight ultrafiltrations of 25 ml. each can be run simultsneously. Te,mperature-eontrolled enoeriments can be Derformed. four a t a time. in the International kortsble Model PR-1 refrigeksted centrifuge.
Bolutions of beryllium were prepared b dilution of a stock solution (6). Suspensions of beryllium hydoldde (Tsble I) were prepared by the addition of 5 ml. of 0.125 M sodium bicarbonate t o each 20 ml. of the appropriate solution of beryllium. The resulting suspensions were allowed t o stand 2hours before ultrafiltmtiotion. It is understood that these suspensions were not pure beryllium hydroxide, but rather a mixtore of beryllium hydroxide and b a i c carbonates.
OF BAG IN ULTRAFILTER
I C 1 POSITION
MEI'HOOS
