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INDUSTRIlL AND ESGINEEIIIKG CHEMISTRI-
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According to the above-mentioned relations betn-een D,E, and F , the coordinates of the center and the diameter of the ring, these latter values are computed from these figures. The coordinates of the center are 19.73 and 25.4, and the diameter of the ring is 26.47 mm. A less accurate but more convenient nietliod is the geometrical determination of the center and the diameter found by plotting the three points n-ith a large scale on coordinate paper. By using millimeter coordinate paper and a 10-time magnification, the results are 19.75 and 25.4 for the center coordinates and 26.3 mm. for the diameter of the ring. For the construction of relative light transmission graphs the horizontal and the vertical scales are now set for the coordinates of the center and the transmission of the center area is read on the scale of the ammeter. The center area has been protected by lead against the x-ray beam. Successive readings are made along the vertical or horizontal radii. The ratio of the ammeter readings for any point as compared to the center \vi11 yield the relative transmission of this point. By subtracting the stage scale readings for a given point from the respective center coordinates, the radius of the point, is determined. By plotting the relative transmissions against the distances of points from the center a curve is obtained, which graphically represents the brightness of the diffraction rings. The maxima and minima of this curve will indicate the diameters of the diffraction rings of the plate. In event of diffraction patterns which are not circular the same fundamental method is used, but more points must be used according to the pattern involved.
Data A graphical description of a n x-ray diffraction pattern is given in Figures 2 and 3. The technique used in making
the x-ray diffraction pattern has been described beforc (4). The dl-P-phenSlalanine is a preparation from the Eastman Kodak Company viliic*hhas been used before in iiltraspectrographic work (3).
Acknowledgment These investigations have been made possible through x grant of the Yational Research Council, Committee on Radiation, to one of the authors (Sp.-d.).
Literature Cited (1) K a t s , J. R., “Die Roentgenspektrographie als Untersuchungsmethode bei hochmolekularen Suhstanzen, hei Kolloiden und hei tierischen und pflanslichen Gem-eben”, in Abderhalden’s “Handbuch der hiologischen Arbeitsmethoden”, -4ht. 11, Physikalische Methoden, Teil 3, Heft 6, p. 222, Berlin, Urban & Schxaraenberg, 1934. ( 2 ) Sisson, IT. A . , and Clark, G. L., ISD. ENG.C H m r . , Anal. Ed., 5, 296 (1933). (3) Spiegel-ddolf, RI., Biochern. J., 31,1303 (19373. (4) Spiegel-Adolf, M., and Henny, G. C., J . Am. Chena. .z’oc., 61, 2175 (1939). ( 5 ) TTeigert, F., “Optische Methoden der Chemie”, Leipsig, Akrtrlemische Verlagsgesellschaft, 1927. FROM the Department of Colloid Chemistry, D. J. McCarthy Foundation. and the Department of Ophthalmology, Temple Cniversity School of Medicine, Philadelphia, Penna.
Sealable Absorption Microtube ARTHUR N. PRATER, California Institute of Technology, Pasadena, Calif.
S
I N C E the development of combustion microtechnique by Pregl, numerous investigators have proposed modifications of the absorption tubes. Most of these tubes have been designed to seal the absorbing agents from the air at all times except during the actual combustion. Through the use of a closed-type absorption apparatus, diffusion from the tube is eliminated, allowing the comout in oxygen alone. While the Pregl tube (3) is unquestionably the simplest and easiest to manipulate, the Tube - 9 , 5 mm, combustion must be finished I n n e r Tube - 8 . 0 m m . o , o . O v e r e l l lenqth - 14C m , with air and temperature changes must be avoided when transferring between the combustion train and the balance room. These objectionable features are entirely overcome by the absorption tubes proposed by Friedrichs (2) and modified by Abrahamczik ( 1 ) . As reported b y Friedrichs, however, the tubes are of such small capacity that too frequent filling is necessary. The modification proposed by Abrahamczik has several distinct drawbacks: It is expensive to construct, very fragile, extremely difficult to fill, and difficult to wipe without accidentally dislodging the sleeve and wiping away some of the lubricant. Modified Friedrichs absorption tubes possessing none of these disadvantages have been used successfully in this laboratory for the past year. These tubes are constructed Closed
from thin-walled hydrometer tubing and when full weigh less than 15 grams, although they contain sufficient absorbent for twenty-five analyses. On standing overnight these tubes. \Then closed, increase in weight only about one quarter as much as do the regular Pregl tubes with the protecting rubber stoppers. The illustration gives the design and dimensions. I n use, all the absorbent is placed in the inner sleeve with the top and bottom protected b y cotton plugs. The lower portion of the ground joint is lubricated with a good grade of stopcock grease, care being taken to prevent grease from touching the portion of the ground surface above the protecting groove. Table I gives typical results with tubes of this design. TABLE I. TYPICAL RESULTS~ Theory Adipic acid Acetyl salicylic acid Acetanilide
a
Found
%
%
C, 4 9 . 3 1
C, 4 9 . 2 4 , 4 9 . 3 1 , 4 9 . 1 9 H , 6 . 9 7 , 6.90, 6.77 C, 59.85
H, 6 . 9 0 C , 59.98 11, 4 . 4 8
C, 71.07 H. 6.72 Microanalyses by G. h. Swinehart.
H, 4 . 6 1
C, 70.96 H, 6.67
I n addition to their use in micromethods, these tubes have proved to be admirably suited for semimicroprocedures. I n this case the tubes are preferably made somewhat larger, the inner and outer t’ubes being 10 mm. in outside diameter and 12 mm. in inside diameter, respectively. Both the micro- and semimicrotubes may be purchased from the Greiner Glassblowing Laboratory, 255 West, Santa Barbara Ave., Los dngeles, Calif.
Literature Cited (I) Abrahamcsik, E., .lfikrochemie, 22, 227 (1937). (2) Friedrichs, A , , I b i d . , 19, 23 (1935). (3) Pregl and R o t h , “Die quantitative organische Mikroanalyse”, 34, Berlin, Julius Springer. 1935.
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