Microfractionating Column for Liquids Having Low Heat of Vaporization PAULE. WESTON Chemistry Department, P u r d u e University, and The Purdue Research Foundation, Lafayette, Ind.
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HIS small fractionating column was designed and made especially for the analysis of butenes according to the method of Dillon, Young, and Lucas (2), in which it is necessary to distill the butylene bromides under reduced pressure. Less than 10 ml. would be sufficient for an analysis if this amount could be d i s t i l l e d satisfactorily. A n o t h e r microcolumn has L b e e n described by Cooper and Fasce ( I ) , but this new column is somewhat easier to manipulate, especially with r--liquids having a low heat of vaporization, and gives about the same separation.
lines. All the vapor is condensed in the small water-jacketed condenser E and, as the liquid flows back over the entrance to the capillary stopcock H , some of it is withdrawn into the receiver, while the rest runs down the column. The receiver is a water-jacketed 5-mm. buret exactly as described by Cooper and Fasce. OPERATION The sample, about 10 to 15 ml., is placed in a 20-ml. flask, attached to the column, and heated by a microburner protected from drafts by a glass chimney (not shown). At first the stopcock H is closed so that all of the condensed liquid refluxes. The flame is adjusted to give a reflux of
DESCRIPTION T h e new c o l u m n i s i n general like the one of Cooper and F a s c e , but it d i f f e r s s h a r p l y in t h a t total condensation occurs a t the head of t h e c o l u m n i n s t e a d of partial condensation, and all the vapor must flow past the bulb of the t h e r m o m e t e r i n s t e a d of o n l y the small FIQURE 1. MICROFRACTION-f r a c t i o n going into the reFIGURE 2. DISTILLATION CURVEOF ~-CHLOROBUTANE AND ATING COLUMN ceiver. This insures correct 2-CHLOROBUTANE temmrature readings w i t h all substances, but some of the rechication is loscthrough about 20 to 40 drops per minute a t the point C, then the elimination of partial condensation. stopcock H is opened by tapping it gently with a pencil The column itself is of the Vigreaux type, 7 mm. inside until distillate drops into the receiver at a rate of about 4 diameter and 34 cm. long from A to B (Figure l), made by to 10 dvops per minute. It is extremely important that B heating small spots on the tube and indenting them with reflux ratio of a t least 4 be maintained, or separation of the a wire. The upper end of the column is expanded into a components mill be very poor. For high-boiling liquids the bulb, C, into which is sealed chromel coil s h o u l d be a tube cut diagonally to a heated to about 20" below 84 point t o p e r m i t observa0: 2 the observed boiling point. $82 For distillation a t reduced tion of t h e r e f l u x . The uppermost tube, D, is about pressure, t h e p u m p i s 3 mm. larger inside diameconnected t o b o t h vent 3 80 ter t h a n the A n s c h u t z 6 tubes, L and M . In plotthermometer which it can78 ting c u r v e s , allowance tains. The whole column k s h o u l d be made for the is enclosed in an evacuated small amount of liquid held j a c k e t a r o u n d which is in the capillary of the stopwound, on asbestos paper, cock H. a heating coil of No. 30 74 chrome1 wire. A test tube TYPICAL RESULTS i n v e r t e d over the therg72 mometer protects it from a The two examples given 70 below were chosen bedrafts, while t h e column itself is packed in insulating DlSTlLLATE-ML. cause they represent FIGURE3. DISTILLATION CURVEOF ANILINE AND typical d i f f i c u l t cases. material in the 10-cm. stove pipe indicated by dotted NITROBENZENE Obviously a mixture such
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179
ANALYTICAL EDITION
180
as methanol and water can be separated with ease. Figure 2 shows the boiling point curve obtained in the distillation of a mixture consisting of 5 ml. of 2-chlorobutane and 5 ml. of 1-chlorobutane. This mixture is very difficult to handle because the boiling points lie only 10" apart, and the heat of vaporization is low, Figure 3 shows the curve for a mixture of 5 ml. of aniline and 5 ml. of nitrobenzene a t 10 mm.
Vol. 5 . No. 3
pressure. The hold-up in this case was greater because these substances are rather viscous.
LITERATURE CITED (1) Cooper a n d Fasce, IND.ENQ.CEW., 20, 4.20 (1928). (2) Dillon, Young, and Lucas, J. Am. Chem. S O C . , 52, 1953 (1930). R E C E I V ~December D 27, 1932.
A Rapid Volumetric Method for Determination of Sulfur in Coal and Coke' Comparison of a Modified Benzidine Method with the Standard Methods EVALD L. SKAU,Department of Chemistry, Trinity College, Hartford, Conn., AND I. LAIRDNEWELL,The Henry Souther Engineering Company, Hartford, Conn. compounds (4 I g ) , pyrites (10, LTHOUGH the generally A new modijication of the benzidine sulfate $7, 28, gg), PaPer-mill liquors adopted methods forthe method has been developed for the determination (23),oils ( 4 ) ) and coal (12, 26). determination of sulfur of sulfur in coals and cokes. Being a volumetric One of the faults of the benziin coal and coke are entirely method, it is rapid and Particularly suitable for dine method for general use is satisfactory from the standpoint routine determinations. It has the advantage that appreciable amounts of the of accuracy and ease of manipubenzidine sulfate are always lation, they are somewhat timethat it can be used in conjunction with the usual lost in the filtrate [for solubiliconsuming. The methods which calori$c determination, eliminating the timeties see Bisson and C h r i s t i e have been adopted by the consuming barium sulfate precipitation. Re(2) and Meldrum and Newlin can Society for Testing Matesuits have been determined on jfteen coals and ( I @ ] , even though s a t u r a t e d rials, the U. S. Bureau of Mines, cokes of widely varying compositions, and combenzidine sulfate solution may and the American Gas Associahave been used f o r washing tion, all depend upon the oxidapapisons have been made with sulfur values dethe precipitate. It is obvious tion of the sulfur in the coal, and termined by the recognized standard t h a t t h e m a g n i t u d e of t h e the subsequent precipitation as Comparison shows that it may be used as a subresulting depends upon barium sulfate, It is well known for these methods with a great saving of stitUte the volume of t,he original soluthat in order to obtain good tion. It would be expected results the solution containing time. that for equal volumes of soluthe b a r i u m sulfate precipitate should be "allowed to stand for at least 2 hours or preferably tions the absolute error would be the same, but the percentage overnight a t a temperature just below boiling" (2.5). The error would be much greater for smaller sulfate concentrapresent investigation was undertaken to develop a method for tions. This probably accounts for the fact that Heczko ( I O ) , the determination of sulfur in coal and coke which would for example, recommends the presence of not less than 0.3 be satisfactory not only from the point of view of accuracy gram of sulfuric acid for satisfactory results by the benzidine and of ease of manipulation, but also from the standpoint of method. This source of error has been practically eliminated in the procedure described below, since the original solution the time element. This investigation was directed toward the development of containing sulfate ions is made up with a saturated solution a suitable volumetric method, since this would be particularly of benzidine sulfate. This would not have been possible if advantageous for routine determinations. The methods in- the original oxidation of the coal had been carried out by the volving the formation of sulfides by a thermit reaction with Eschka or sodium peroxide fusion method, in which case an subsequent evolution of hydrogen sulfide and titration require additional error might have been caused by the presence of a a very precise and difficult technic to produce satisfactory high concentration of salts. results. Titration of sulfates with barium salts is subject In order to give the method a thorough test, determinations to interference by appreciable amounts of calcium, nitrates, were made on a large variety of coals and cokes varying not only in sulfur content but also in proximate analysis. Inor ammonium chloride (11). The authors' attention was called by V. K. Krieble to cluded in these were four coal samples which were supplied several published accounts on the determination of soluble with complete analysis through the courtesy of H. M. Cooper sulfates by the use of benzidine. The method seems first of the U. S. Bureau of Mines. to have been proposed by Miiller (19) and was later modified For purposes of comparison, sulfur determinations were by Raschig (232,von Knorre ( I J ) , and Friedheim and Nydeg- made by means of the standard bomb-washing and sodium ger (7). Subsequent applications of the benzidine method peroxide methods ( l ) as , well a8 by the new bensidine method. and modifications included the determination of sulfur in I n the case of the Bureau of Mines samples, they were made biologic liquids (3, fi, 9, IS, I,5, 20, 21), rubber (I?'), organic by means of the Eschka method (6). 1 The preliminary experiments in this investigation were carried out by The results indicate that this new method can be used the senior author in 1920-21 a t The Emerson Laboratories, Springfield, satisfactorily as a substitute for these standard methods. Mass.
A
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