November 15, 1942
907
ANALYTICAL EDITION
Part of the dithizone solution (2 ml. of the 0- to 10-microgram solution, or 10 ml. of the 0- to 50- or 0- to 100-microgram solution) is used to flush the stem of the funnel; the end of the funnel stem is dried, and the solution is allowed to runfdirectly into the proper cell for the photometric reading. The 0- to 10microgram solution is used with a 5-cm. (2-inch) cell, the 0- to 50-microgram solution with a 2.5-cm. (1-inch) cell, and the 0- to 100-microgram solution with a 1.25-cm. (0.5-inch) cell. The cells are cylindrical, with optically plane ends and have an internal diameter of about 14 mm. Since the 0- to 10-microgram cell holds the entire 8 ml. remaining in the funnel, it cannot be rinsed with part of the dithizone solution, but must be cleaned and dried with pure acetone after each sample. The other two cells, however, can be rinsed with dithizone solution a t least twice, and it is rarely necessary to wash or dry them between sam les. Tge photometric readings are referred to calibration curves made for each standard solution in the following way: A standard lead nitrate solution is made by dissolving recrystallized lead nitrate in 1 per cent nitric acid, so that each milliliter contains 1 mg. of lead. From this solution two dilutions in 1 per cent nitric acid are made, one containing 10 micrograms of lead per milliliter, and the other 1 microgram per milliliter. All these solutions will keep indefinitely in glass-stoppered Pyrex containers. A standard lead solution in the proper buffer is made by taking a measured quantity of the desired standard lead solution, bringing it to pH 3.4 by addition of dilute distilled ammonium hydroxide, adding the proper amount of the Clark and Lubs buffer mentioned above, and diluting the mixture to a known volume. This solution should be made fresh each time it is used. Measured quantities of this standard lead solution are added to clean separatory funnels, the volume in each funnel is brought to 50 ml. with the pH 3.4 buffer solution, and the dithizone solution to be standardized is added. Color development and photo-
metric readings are then carried out as in the final estimation of lead. From these readings a standard calibration curve can be made. Summary Certain modifications of the photometric dithizone method previously described are discussed. The observance of certain precautions makes it possible t o keep standard dithizone solutions for months without apparent deterioration. The time required for carrying out an analysis has been decreased significantly by the development of a lead-bismuth separation which permits the omission of the bismuth test. The complete analytical procedure, including preparation of samples and purification of all reagents-previously described in several papers-is given in detail.
Literature Cited (1) Bsmbach, Karl, IND.ENO. CHEM.,ANAL.ED., 11, 400 (1939). (2) Cholak, J., Ibid., 7, 287 (1935). (3) Cholak, J., and Story, R. V., Zbid.. 10, 619 (1938). (4) Clifford, P. A., and Wichmann. H. J.. J . Assoc. OfficialAer. Chem., 19, 130 (1936). (5) Hubbard, D. M., IND. ENO. CHEY., ANAL.E D . , 9, 493 (1937). (6) Kehoe, R. A., Thamann, F., Cholak, J., J . Znd. Hyg., 15, 257 (1933). ---, (7) Kluchesky, E. F., Longley, B. J., and Kozelka, F. L., J. P h r macol., 74, 395 (1942). (8) Smith, F. L., 2nd, Rathmell, T. K.,and Williams, T. L., Am. J. Clin. Path., 11,653 (1941). (9) Wichmann, H. J., IND. ENO.CHEW.,ANAL.ED., 11, 66 (1939). (10) Willoughby, C. E., Wilkins, E. S., Jr., and Kraemer, E. O., Ibid., 7,285 (1935).
.
A Simple Apparatus for Small-Scale Catalytic Hydrogenation C. R. NOLLER
N
AND
hi. R. BARUSCH, Department of Chemistry, Stanford University, Calif.
UMEROUS designs of apparatus for small-scale cata-
lytic hydrogenation have been described in the literature, a good survey of which has been given recently by Johns and Seiferle (f). W ile no claim is made for great originality in t h e apparatus now described, the authors believe that they have combined the good features of several types of apparatus and modified them t o give one which is very simple in construction and operation (Figure 1). One of the inconveniences of most designs is the shaking mechanism, which usually is of the reciprocating type. Weygand and Werner (2) used an electromagnetic stirrer. The authors have substituted a medium-size Alnico permanent magnet for the electromagnet, and in place of the complicated devices for introducing the sample or catalyst have used a cup and stopcock. The type of buret used by Johns and Seiferle (1) has been retained, since this avoids the use of a stopcock. As usually operated, the weighed sample to be hydrogenated is placed in the flask with a suitable solvent and the iron-cored stirrer. With the stopcock open, the flask is connected to the buret by the ground joint and held in placed with a buret clamp. The reservoir is lowered, the height of the magnet is adjusted, the stirrer is started, and the speed of the motor is regulated so
A.
B. C. D. E. F. If. L. M. N.
FIQURE 1. APPARATUS 50-cc. buret 50-cc. flask 19/38 interchangeable ground joint 5-cc. cup %om. section of 8 d. nail sealed in glass tubing Medium size Alnico magnet Brass saddle with setscrews 1/100 h. p. variable-speed motor Hydrogen inlet To reservoir for confining liquid
PL
908
Vol. 14, No. 11
INDUSTRIAL AND ENGINEERING CHEMISTRY
that good stirring is obtained without throwing the li uid too high up the sides of the flask or causing the magnet tolose the stirrer. The apparatus is swept out with hydrogen which has been saturated with the solvent used in the flask by bubbling through a wash bottle having a fritted-glass distributor. The confining liquid in the reservoir may be either mercury or solvent. After the air has been swept out, the desired amount of hydrogen is trapped in the buret, the stopcock on the flask is closed, and stirring is continued until the volume of hydrogen as read on the buret no longer changes, a t which time the stirring is stopped and the temperature and barometric pressure are noted. After slightly reducing the pressure in the flask by lowering the reservoir, the latinum oxide or alladium oxide catalyst is introduced by tEe following procelure: The catalyst is wei hed into a narrow glass or metal scoop and a measured volume ofsolvent, usually 5 cc., is drawn into a pipet. A few drops of solvent are run into the cup, the catalyst is added, and the scoop is washed with a few more drops of solvent. The catalyst is then drawn in through the stopcock and washed in with the remainder of the solvent, care being taken not to admit air. This procedure has the advantage of permitting reduction of the oxide catalyst in the presence of the compound t o be reduced, which gives a more active catalyst than reduction in solvent alone. It was not found
possible t o have the catalyst present while the apparatus is being swept out with hydrogen, because the rate of solution and diffusion of hydrogen is so great that hydrogen is absorbed at the rate of about 0.5 cc. per minute even without stirring. After addition of the catalyst, stirring is started and continued until hydrogenation is complete, when the volume, barometric pressure, and temperature are read again. The volume of the catalyst and wash solvent and the hydro en absorbed by the catalyst and solvent are determined in a blant run. While this apparatus has been used only for semimicro work and not for measuring the volume of hydrogen absorbed with great accuracy, there seems to be no reason why it cannot be adapted to micro work or why it should not yield results as accurate as most other forms of apparatus, if the corrections and calculations described by Johns and Seiferle (1) are applied.
Literature Cited (1) Johns, I. B.,a n d Seiferle, E. J., IND. ENQ.CHEM.,ANAL.ED., 13, 840 (1941). (2) W e y g a n d , C., and W e r n e r , A., J. ptakt. Chem., 149,330(1937).
Quantitative Decomposition of Organic Bromine and Iodine Compounds by the Lime-Fusion Method WILLIAM M. MAcNEVIN AND GLENN H. BROW", Department of Chemistry, Ohio State University, Columbus, Ohio
T
HIS paper presents data to show that the lime-fusion method of decomposing organic compounds of chlorine
TABLE11. DETERMINATION OF IODINE
(1) can be applied to the analysis of similar compounds of
bromine (Table I) and iodine (Table 11),and also describes an improvement in the bomb for heating the sample with lime and a method for testing i t for leaks. Semimicrosamples have been used throughout. The construction of the bomb has been modified by providing the contact face of the bomb chamber with a sharp ridge approximately 0.5 mm. in height. When the bomb is closed, this sharp ridge is embedded in the copper washer and a tight seal is thus easily obtained. Bombs, especially when new, should be tested occasionally in the following way for the tightness of the seal. This test for tightness is strongly recommended to those who use the bomb for the first time. The bomb is half-filled with dry ice, sealed, and inverted in a beaker of warm water. If bubbles Present address, Department of Chemistry, University of Mississippi, University, Miss. 1
TABLE I. DETERMINATION OF BROMINE Weight ComDound Hexabromoethane Tetrabromobutane hlonobromobenzenea Bromomesitylene a I-Bronio-2,7-dimethylnaphthslenea 1-Bromo-4-nitrobenzene0 p-Bromoacetanilide 0
of
Weight of AeBr
10.87 12.21 17.35 20.31 23.58 17.80 22.91 22.43 15.43 16.23 14.67 15.80 11.92 11.44 15.58 17.22
SamDle Mi.
Br Theoretical
Mg.
Br Calculated %
%
%
24.27 27.25 34.83 40.80 28.11 21.12 21.48 21.09 12.17 12.90 13.58 14.64 10.53 10.08 6.38 7.08
95.01 94.97 85.44 85.49 50.72 50.49 39.89 40.00 33.56 33.83 39.38 39.43 37.59 37.48 17.43 17.49
95.23
-0.22 -0.26 -0.09 -0.04 -0.19 -0.42 -0.24 -0.12 -0.43 -0.16 0.19 -0.14 +0.24 4-0.13
Research compound, CsHloOsBr 4 100 mg. of KNOa added to ignition mixture.
85.53 60.91 40.15 33.99 39.57 37.35 17.40
Difference
-
+0.03 +0.09
Compound0 p-Iodonitrobenzene p-Iodoaniline 8-Iodopropionic acid Methyl-p-iodobenzoate p-Iodoazobenaene p-Iododiphenyl 0
Weight of Sample
Weight of AgI
I Calculated
I Theoretical
MO.
Me.
%
%
70
20.32 21.04 15.86 20.12 15.86 15.71 18.00 26.03 16.97 4.92 12.91 14.93
19.12 19.92 17.02 21.55 18.67 18.36 16.05 23.25 12.93 3.75 10.79 12.50
50.87 51.18 58.01 57.90 63.64 63.18 48.20 48.28 41.19 41.20 45.18 45.26
50.97 57.98
-0.10 +0.21 4-0.03 -0.08
63.46
+0.18
48.43
-0.28 -0.23 -0.15
41.19
Difference
+o.oo
+0.01
45.31
-0.13 -0.05
100 mg. of KNOa added to ignition mixture in every case.
do not appear, it may be assumed that the method of closing the bomb is satisfactory. The analytical method of determining the halogen in the ignition product is the same as that described earlier for chlorine ( I ) , except that provision is made for the reduction of possible bromate and iodate. The reduction is carried out by adding 200 mg. of hydrazine sulfate (Eastman) to the water suspension of the ignition product and warming the mixture to 75" to 85' C. for 5 minutes. The calcium oxide suspension is then cooled under tap water and dissolved with stirring in the minimum amount of nitric acid. Fine grinding of the sample and its intimate mixing with the calcium oxide have been found necessary for obtaining satisfactory results. It is also recommended that a blank be determined on the combined reagents. The method has i f i c i e n t accuracy for the determination of the number of halogen atoms in the organic molecule.
Literature Cited (1) MacNevin, W. M., a n d Baxley, W. H., IND.ENQ.C ~ M ANAL. .,
ED.,12, 29 (1940).
