V O L U M E 21, NO. 8, A U G U S T 1 9 4 9
1015
operated above 30 volts a water jacket or air blast should be P d e d to prevent overheating of the windings of the stator and oosening of the wax seal of the armature housing. This stator is supported in the usual manner or on a collar (a cork ring) which rests on the reaction equipment. S o alignment problem is encountered when the stirrer is assembled in the latter fashion. The power supply for the stator is conveniently made from a variable transformer and a 50-100pF oil or paper condenser (Figure 5). (Pyranol Capacitor, Catalog S o . 67X18XJ Model 9CElA318, 330 volts, 60 cycles, 50pF). This arrangement is ti typical capacitor induction type motor circuit and permits operation of the motor on a 110-volt, 60-cycle single-phase line.
5 0 TO l O O p f O I L F I L L E D CONDENSER
01
Figure 3.
Armature
llo I
[*42
1
i 0941 D R I L L
4-40
NC TAP
4
Dp DP
4 HOLES E C U A L L Y ON D B C
60 SPACED
I 1
4
GLASS
DRILL 4
W E
THRU
HOLES
1 4
--
I
I
Figure 5 . DRILL $ 0 ,
I
;1
SELSYN GENERATOR STATOR
CYCLES
VARIABLE TRANSFORMER
-14WITH
I
Wiring Diagram
Stirrers. Many types of stirrer assembly may be used Lzith this motor. The stirrers are connected to the drive shaft of the motor by means of a ground joint and the joint is held together with a low melting solid (such as de Khotinsky cement or sealing wax). This method of connection allows for attaching diffrrent stirrers without opening the armature housing.
REF DlA
LITERATURE CITED
EQUAL TO O D OF GLASS W E L L
Figure 4.
Cap
Stator. The stator is the field coil of a selsyn generator Model 2555V1, 110 volts, 60 cycles, General Electric Co., Schenectady, PIS. Y., 1.5-inch inside diameter). When the unit is
(1) Dauben, W. G., Reid, J. C.. and Yankwich. P. E., 19, 828 (1847).
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C'Hb:>r.,
RECEIVED September 3, 1948. Based on work perforiiied under euntra('t No. W-7405-Ene48 with t h e Atomic Energy Commission in connection with t h e Radiation Laboratory. University of California, Berkeley, Calif.
Modified Method of Charging the Poth Carbon Dioxide Generator P. L. PICKARD, T h e University of Oklahoma, .Vorman, Okla. S 1930, Poth ( 2 ) described a generator "which enables one to
store a quantity of carbon dioxide with complete assurance that it will represent a gas of consistent high purity" for use in microanalysis of nitrogen by the Dumas method. The generator has since been modified (3). This author's first experience with the modified form of the Poth generator was with a commercial model which had been discarded because the difficulty of charging according to the directions given had led to the conclusion that it was incorrectly built. After several attempts the generator was successfully charged and served for the duration of a problem which involved an extraordinarily large number of nitrogen analyses ( 1 ) . Because new generators from the same source (Scientific Glass Ipparatus Co.) have caused similar difficulty, a method of charging has been developed xhich is considered more convenient and rapid than that described by Poth. K i t h the generator (Figure 1)lying horizontally so that opening E is a t the top, a solution of 1 to 2 sulfuric acid in water is sucked into B by connecting D to an aspirator. The acid solution is not cooled after mixing, as the heat generated aids in exclusion of air from the apparatus. The generator is then raised to a vertical position, the aspirator is connected to C, and 1200 ml. of a hot a t u r a t e d solution of potassium bicarbonate are sucked into A . A few milliliters of water are pulled into A to rinse the bicarbonate from D. Sufficient water is added to D to cover the tip of the bubbler. Mercury is added to C until the level is about half-way to the
upper end of F . C' is connected to the leg of a T-type three-\\ ay stopcock. One arm of the stopcock is open to the atmosphere and the other connected through a T joint to a vacuum uumu which is adequately prbtecied hy a drying column. The other leg of thc T joint is connected to D . With Z) and I.' closed the varuum pump is started and I' openrd into C very cautiously to prevent too violent b u m p ing of the mercury. After the generator has txhtsn evacuated several minutes, D is opened slightlv. I3y adjusting I),the level of hu1furic acid in E may be maintained nearly constant. ;hould the lrvel of acid in E rise, D should bta shut off momentarily. After 15 minutes' evacuation, D and then Y are closed. D is opened slo\vlp, with the pump still operating, and acid is pulled up into E. As soon as a drop of acid falls, D is closed and the carbon dioxide evolved bubbles back through E and Figure 1 F to equalize the
1016
ANALYTICAL CHEMISTRY
pressure. D is again opened and the process is ropeatEd several times. With D closed, Y is opened slowly to the atmosphere. If the pressure in the generator is insufficient, mercury nil1 be farced up into F , and more acid must be pulled into A as before. If the pressure exceeds atmospheric bv a n bmount greater than the height of mercury in C, carbon dioside --ill bubble through thc mercury until ecluilibrium is attained. C and D are disconnected and more mercu'ry is added to bring the level about to the top of F. The small amount of sulfuric acid solution on the morcury may be removed by a cotton swab. Carbon dioxide is evolved more rapidly than it escapes through D. Consequently, while the generator is in use excess gas escapes through the mercury seal each time acid drops into the bicarbonate. Rapid delivery of gas causes largc amounts of
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. ,.
~
..
. ... .. .
acid to be pulled into the bicarbonate and usually results in expulsion of mercury irom the scal and contsminnt,ion of the generator with air. To provcnt this it is advisable to conncct a section ai capillary (a broken thermometer serves this purpose admirably) to D ,so that gas may not be delivered more rapidly than is ordinarily rcquircd far the Dumas micropiondure. LITERATURE CT
(11 Pieksrd, P. L., and Loohte, H. L.. (1947). ( 2 ) Poth. E. J., IKD.ENC.C n m ~ANAL. , Lu.,-, (3) Ibid.. 3, 202 (1931); 11, 518 (1939).
\3v.,yI.
R ~ c a r v e oSeptember 20. 1948
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x.. 69, 14
.
.
. . .
21. o-Aminobenzoic Acid)
ic
A
0-AMINOBENZOIC ACID I1
'The commercial material usually contains modification I11 in largest amount, and verylittle modification I. Modification I is, hovever, the stable form at room temperature. o-AMINOBENZOIC ACID I
CRYSTAL MORPHOLOGY (determined by W. C. McCrone). Crvstal Svstem. Orthorhombic. Fdrm a n d Habit. Plates or tablets from water lvine on 100: rods elongated parallel to c. Shows the forms: m&r@inacoid; 11001; brachypinacoid, (010); hipyramid, (221). Axial Ratio. a:b:c = 0.838:1:0.724. 0.6066:1:0.8715~1). Interfacial Angles (Polar). 101 A TO1 = 81.6'; 021 A 021 = I l " Q 0
IIV.0
CRYSTAL MORPHOLOGY (determined by W. C. McCrone). Crystal System. Orthorhombic. Form and Habit. Rods and needles elongated pamllel to c; shows hrschypinacoid, { 100); macropinaeoid, (OlO} and hipyramid, ( I l l } . Axial Ratio. a:b:c = 0.727:1:0.447. [These ratios agree well with Groth (1)if a and b are reversed and our a douhled.1 ~ ~ t ~&ies~ (polar), f ~ ~ 011 i A~ 07l1 = 48.20; 101A i01'= 63.2".
-.
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. I
.
.- .
w00
'
. .,.
'
k
,
rn
0 0
.
X-RAY DIFFRACTION DATA(determined bv W. C. Mecrone. I. Corvin, and J. Whitney). Space Group. C:v (3). Cell Dimensions. ao= 10.79 A,; b = 12.87 A,; c = 9.32 A. a = 9.4 b = 10.8 A: c = 12.8 b. (3). Formula Weights per &ell. 8. Formula. Weieht. 137.13. Density. l.dO8; 1.412 ( 1 )
x.;
d
8.02 7.58 6.03 5.81 5.29 4.71 4.03 3.79
Principal Linea I/II d 0.45 3.62 Very weak 3.46 0.63 3.34 0.76 3.17 Very weak 3.04 Very weak 3.00 0.80 2.83 0.49 2.76
3
w -
I/Il Very weak Y a y weak 1.00 0.47 0.11 Very r e s k
Very weak Very weak
OPTICAL PROPERTIES (deterpined by W. C. McCrane). Refractive Indexes (5893 A.; 25" C.). a = 1.500. B = 1.74. y = 1.77. Optic Axial Angles (25" C,), 2V = 39" (D); 2 8 = 70" (red); 68" ibluei. Dkpersion. 7 > u. Optic Axial Plane. 001. Sign of Double Refraction. (-). Acutc Bisectrix. b.
d
Figure 1. v-Aminobenzoic Acid
0
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