Recommended Specifications for Microchemical Apparatus Micro-Kjelda hl Nitrogen Committee for the Standardization of Microchemical Apparatus, Division of Analytical SOCIETY Chemistry, AMERICANCHEMICAL AL STEYERMARK, Chairman, Hoffmann-LaRoche, Znc., .Vutley, IV. J . H. K. ALBER, Arthur H. Thomas Go., Philadelphia, P a . V. -4, ALUISE, Experiment Station, Hercules Powder Go., Wilmington, Del. E. W. D. HUFFAIAN, Huffman Microanalytical Laboratories, Denver, Colo. ,J. A. ICUCIC, College of the City of New York, N . Y., and American Cyanamid Co., Stamford, Conn. J. J. MORAR', Kimble Glass, Division of Owens-Illinois Glass Go., Vineland, IV.J . C . 0. WILLITS, Eastern Regional Research Laboratory, Philadelphia, Pa.
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APPROX.
IMM
APPROX SANDBiAST?D I S CM AREA (FOR LABELLING)
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I5f0.5MM 0.0. WALL 1.0-1.3MM
L
11
5 0 t MM 40fZMM
The heaters must maintain a mixture of 2 ml. of sulfuric acid plus 1.30 grams of potassium sulfate at its boiling point (350" C.) The heaters must be sufficiently adjustable to provide for a mild digestion (low temperature) as well as distillation rates that will maintain refluxing of the acid into the neck of the flask. To avoid excessive heating of the flask necks, a shield is provided above the heaters. The shield should have circular openings not to exceed 26 nim in diameter, directly above each heating element. The openings must be spaced 67 * 7 mm. on centers. The rack must be provided with deflectors mounted under the burners to prevent overheating of the bench top. Gas Heaters. The burners should be individually adjustable, with handles conveniently located at the front of the rack, and so constructed that they will be cool enough to manipulate even after long periods of operation. The burner must produce a nonluminous flame. Electric Heaters. Electric heaters must perform satisfactorily at 100 volts. The controls must be convenientlv located and should not become too hot to handle on continued op-
-1 Figure 1. 10-M1. Kjeldahl Flasli
R
b 2 1 . 5 M M MAX.
Figure 2. 30-MI. ICjeldahl Flasli
ECOMMENDED specifications for microchemical appara-
tus used in the carbon-hydrogen, Dumas nitrogen, halogen, and sulfur determinations ( 8 ) and the proposed program for the future ( 1 ) have been published. The present paper includes recommendations for the apparatus used in the Kjeldahl nitrogen determination and includes the following: Kjeldahl digestion flasks, 10, 30, 30 (Soltys), and 100 ml hlicro digestion rack Manifold for micro digestion rack Micro-Kjeldahl distillation apparatus, Pregl Type (ParnasWagner); electric steam generator Micro-Kjeldahl distillation apparatus (one-piece model)
All recommendations have been made only after considerable experimental work by members of the committee. Kjeldahl Digestion Flasks. Specifications for four types of flasks are recommended-10, 30, 30 (Soltys), and 100 ml. These are shown in Figures 1, 2, 3, and 4. Micro Digestion Rack. The following specifications are recommc.nded. The micro-Kjeldahl digestion rack should be portable and consist of two parts, the flask heaters and the manifold support. The rark should provide for six Kjeldahl flasks, capacities 10 to 100 ml. HEATERS.The source of heat may be either electricity or gas.
Figure 3. 30-M1. (Soltys) Kjeldahl Flask
523
ANALYTICAL CHEMISTRY
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Distillation flask, G Filling funnel, H Condenser tube (glass or silver), J Condenser jacket (West type), K Drain, L
eration. Not more than two heaters should he ODerated from one set of controls. MANIFOLD SUPPORT.This must hold the manifold securely, and also he adjustable, so that the manifold will support all the recommended sizes of flasks at the proper angle during digestion. Manifold for Micro Digestion Rack. Figure 5 shows the recommended manifold. Any of the four types of Kjeldshl digestion flasks may he used with it.
LL;.5
A new type of generator is recommended that provides closcr control of steam generation than tho usual gat-heated distillation flask. This all-glass steam generator, Figum 7 A , is a widemouthed commercially availahle resin reaction kettle (Corning Glass Works, Corning, N. Y.). The intorchsngmh1.blo cover, with flat-ground rim and four ground-glass ;F stopper tuhulnbions,
MM MAX.
20?0.5MM 0.D WALL 1.0-1 5 MM
7
7 0 f 2 MM
-1 Figure 4.
100-MI. Kjjeldahl Flask
Micro-Kjeldahl Distillation Apparatus, Pregl Type (ParnasWagner). This apparatus, shown in Figures 6 and 7, is composed of the following parts: Steam generator (2000-ml. capacity), A Steam Cuhe, B Wiring assembly, C Steam tram .,D Tube, E Connecting tube, F
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Figure 6 . Micro-Kjeldahl Distillation Apparatus, Pregl Type (Parnas-Wagner)
520flOMM
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73f2MM I SLOPE 6-B'MM FOR DRAINAGE
73fZMM
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FORM REINFORCING BEAD
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WALL APPROX. 2 M M
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SECTION A-A
Figure 5.
Manifold for Miwd-Kjeldahl Digestion Rack
V O L U M E 23, N O . 3, M A R C H 1 9 5 1
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CCKTER OPENING T O ACCOMMODATE
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JOINT
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PROVIDE
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140r 3 MM
195hMM
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Figure 7A. Steam Generator, Micro-Kjeldahl Distillation Apparatus, Pregl Type (Parnas-Wagner)
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is held in place with suitable clamps. To the center tubulation is attached the steam tube, Figure 7 B . Two of the outer three tubulations are used for the leads of the electric heater assembly, Figure 7 C . The remaining tubulation is used for a water inlet,
.WALL 5 MM I MM 0.D
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GLAZED
7 E ATTACHED HERE
Figure 7D. Steam Trap
~ O C ~ M M
B t 0 . 5 MM O.D. WALL I M M
GLAZED
resistance of the heating spiral is about 16 ohms. The rate of steam generation is readily controlled by means of a 7.5-ampere variable autotransformer.
I O MM O.D. APPROX.
I
8f-0.5M M O.D. WALL I M M
Figure 7E. Tube
ANALYTICAL CHEMISTRY
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I-
155f3MM
NO 18 CONDUCTOR W I R E
7G CONNECTS HERE
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6.5-7 MM(MAX
SPLICE
WALL I
RUBBER SLEEVE
410
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NO. B W I R E (INSULATED) N0.5 ONE HOLE RUBBER STOPPERS
I N S U L A T I O N CARRIED ROUGH RUBBER S T O P P E R S
FITS INSlDE 7 K
Figure 7L.
Drain Figure 1J. Condenser Tube 73 FITS INSIDE
BRAZE OR SOLDER
l 4 t 2 MM 0.D. WALL IqLMM
40f.2 MM
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. T 4 8 ? 0 . WALL 5 M MI MM .O:
APPROX 2 M M DIA OPENING AT' POlNfS
Figure 7H. Filling Funnel
10 MM APPROX.
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Figure 7K. Condenser Jacket (West Type)
527
V O L U M E 23, NO. 3, M A R C H 1 9 5 1
CONNECTS TO 7F
obtained with a one-piece model by many, inoluding members of the committee, the design was studied. The specifications recommended here are the result of this work. This revised model is used with the electric steam generator, Figure 7 A , forming a sturdy, compact unit. The complete apparatus is shown in Figu r e ~8 and 9.
7
the temperature by a vacuum jacket as in Figure 7G. The Stertm enters
~rouer'(inner jacket). and
D ~ S B ~into S
portion of the tube a t the Gwer end of
Figure 7 6 .
Distillation Has
This &e&m generator is also used with the Kjeldahl di sppmatus, one-piece model (Figures 8 and 91, described Changea have been made in the conventional desigr distillation flask, Figure 7G, and the condenser tube 7 J . They include a ball and socket joint connectio should be lubricabd with stopcock grease and held togel a suitable clamp, and a We?Test-typecondenser. Kjeldahl Distillation Apparatus. ONE-PIECE MODEL(Figures 8 and 9). An apparatus of this type, but having slightly different dimensions, has been commeroidly available for 8ome time (Scientific Glass Apparatus Co., Inc., Bloomfield, N. J.). The origin of this apparatus is unknown, although attempts have been made to establish it. Because excellent results have been
the inner Irtcket. ana UD Into the center Portion or tne u1Stlll&tiOn .~ ~
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chamber or d i s t k i o n flask. The alkali is added in like manner, displacing the acid portion upward. Steam is generated with the stopoocks on both the sample inlet funnel and the drainage tube closed, and the distillation is allowed to proceed.
ANALYTICAL CHEMISTRY
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Several methods of cleaning can be used. The following one has been found satisfactory, particularly when boiling chips are em loyed in the digestion: W h i i steam is being generated and with both stopcocks closed, the sample inlet funnel is filled with water and the tip of the condenser immersed in about 100 ml. of water contained in a beaker. Steam generation is stopped, and stopcock of the funnel is opened slowly, being closed before all the water has drained into the apparatus. Reduced pressure causes water to be sucked from the beaker into the apparatus, washing it. The stopcock in the drainage tube is opened to empty t,he liquid which has
collected in the outer jacket, the steam generation is started again, and the procedure is repeated. LITERATURE CITED (1) ANAL.CHEM.,21, 651 (1949).
(2) Steyermark, Al, Alber, H. K., N u k e , V. A , , Huffman, E. W. D., Kuck, J. A., Moran, J. J., and Willits, C. O., Ibid., 21, 1555 (1949).
RECEIVED November 10, 1950
140f5 MM
B E N T BACK
1- 1 I
(CONDENSER OMITTED) IN T H I S VIEW
ir'-
MM O.D.
*WX.
ICLAZED
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PPROX 2 M M SPACE
260 MM RADIUS -l8+2MM
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MM O.D. WALL I MM
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DRAIN 7 L F I T T E D ON HERE
E A L A S POSSIBLE
l i
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c l l r l MM O.D. WALL I MM
.AZED
OMITTED I N THIS VIEW
Figure 9.
Kjeldahl Distillation Apparatus One-piece model
