V O L U M E 23, NO. 2, F E B R U A R Y 1 9 5 1
387
diluted to 190 ml. and 5 grams of hydrouylamine hydrochloride were added. The solutions were then electrolyzed for 1 hour, using platinum gauze cathodes and platinum spiral anodes Two amperes (per sq. dm.) were used during the first 15 minutes and 1 ampere (per sq. dm.) for the last 45 minutes. The electroly-tes u erc stirred by air circulation. After the electrolysis tlir cathodes were immersed in water and alcohol, dried a t 105’ C. for 3 minutes, cooled, and weighed. The current used b j tlie author had an impressed voltage of 9 volts. The voltage across the electrodes was 2.8 volts. The results obtained for antimony are shown in Table I.
chlorine, hydrogen, and oxygen. However, tlic fact that excellent results were obtained indicates that the deposits were very pure. More than 0.4 gram of antimony should not be determined by the method; otherwise high results will be obtained. For instance, the result obtained by the author in electrolyzing 0.5000 gram of antimony was 0.5024 gram. In the sulfide method 0.2 gram of antimony is the masimum amount that can be handled (6). Copper, cadmium, tin, arsenic, le:id, bismuth, and silver interfere with the method, and when they are present, preliminary separations are necessary.
DISCUSSION
When metallic antiinony is dissolved in sulfuric acid, the antimony is in the antimonious state and must be oxidized with hydrogen peroxide. There is little danger of losing antimony by volatilization when the solution is boiled to destroy the hydrogen peroxide ( 4 ) . The amount of sulfuric acid and hydrochloric acid used in the method is not critic:tl. Good results were obtained using 10 t o 20 ml. of sulfuric x i d and 5 to 20 ml. of hydrochloric acid. The exact temperature used during tlie electrolysis is not important. Equally good results wrt, obtained using temperatures varying from room temper:tturc t o 80” C. Tests made with hydrogen sulfide after the electrolyses showed that no detectable amounts of antimony were left undeposited. It was not fwsible to test the deposits for possible occlusion of
LITERATURE CITED
(1) Classen, A., “Quantitative Analysis by Electrolysis,” p. 132, New York, John Wiley & Sons, 1913. (2) Diehl, H., “Electrochemical Analysis with Graded Cathode Potential Control,” p. 45. Columbus, Ohio. G. Frederick Smith Chemical Co., 1948. (3) Henz, F., Z.anorg. Chem., 37,31 (1903). (4) Hillebrand, W. F., and Lundell, G. E. F.,“Applied Inorganic Analysis,” p. 222, S e w York, John Wilcy & Sons, 1929. (5) Schoch, E. P., and Brown, D. 0...I. A m . Chum. Soc,. 38, 1660 (1916). (6) Treadwell, F. P., and Hall, W. T., “Analytical Chemistry,” Vol. TI, p. 213, Scw York, D. Van Nostrand Co., 1930. (7) Willard, H. H., and Diehl, H., “Advanced Quant,itative Analysis,” p. 348, New York, D. Van Sostrand Co., 1943. RECEIVED April 21, 19,513.
Versatile Paper Partition Chromatographic Apparatus ARNOLD J. SINGEK
AND
LEONAKII KENNER
Amni-i-dent, I n c . , Jersey City 6, iV. J .
’HE past few years have seen the increased use of -paper partition chromatography as both a qualitative and a quantitative analytiral micromethod. Coincident with increasing use of this method has been improvement of the apparatus in which the chromatogram is developed. Methods previously introduced
\
FIGURE
I
have embodied the principle of capillary descent (1, 4, 5, 8, 10) and capillary ascent ( 4 , 7 , 9, 11). Sumerous devices for the phase of solvent flow separation have been described, but these provide inadequate space (6, 7), have the paper strips inadequately supported (3, 9, 1 1 ) , or have both disadvantages ( 4 , 7). The authors have constructed a frame for rigid support of the paper a t both ends during the phase of solvent separation by capillary ascent. The frame has the following advantages in the use of paper partition chromatography as an analytical or separatory procedure: Up to 50 one-dimensional chromatographs can be developed a t one time; contamination of the strips by contact with each other or the walls of the apparatus is prevented; there is sufficient vapor space in the apparatus to reduce the effect of slight fluctuations in room temperature on the rate of flow of the developing liquid; the depth of the nick end of the paper in the liquid remains constant; the sample is a t a constant distance on the paper from the solvent; and the paper is supported tightly and vertirally, which eliminates variations in rate of flow due to slope of the paper Ftrips, The frnnie is constructed of 1 x 4 mni. strips of cold-rolled steel. Two strips 73 em. long mere bent into circles having an internal diameter of 22.5 em. and the ends were brazed together. These circles were then brazed to the ends of four strips 50 em. long a t 90” intervals around the circles. Two 3-crn. lerigthsof 4-mm. rod were brazed horizontally on thca top ring a t 180” and two flat “ears” 3 cm. wide, 6.5 cni. long, and 2 mm. thick were blazed on a t 90”. Four 3-cm. lengths of rod w r e brazed horizontally a t 90” intervals on the bottom ring. Thc RJdSwere used as stabilizers to orient the frame in the tank; the ears were used as handles and hangers. Friction tape was wound around both rings and pierced by 2-inch (5-cm.) steel pins pointing toward the center of the frame. The use of tape is suggested for greater flexibility of the apparatus. Similar frames of smaller diameter can be made to telescope nithin the outer frame. These can be used for additional strips and the frames can be removed selectively a t different tinw intervals.
ANALYTICAL CHEMISTRY
388 The developing tank is a borosilicate lass jar, with handles, OIJtained from A. H. Thomas Co., Philajelphia, Pa. (Catalog No. 6289-A,outside diameter 30.3 cm., inside diameter 29.0 cm., hei h t 60 cm.). The handles are 2.5 cm. from the top of the jar a n f a r e formed by indentations of the wall of the jar. These serve as supports for the frame, which is suspended on them by the ears, so that no portion of the frame touches the developing liquid. The top is an ordinary piece of plate glass 12.625 inchw square, which is sealed to the jar with a heavy lubricant to give an air-tight seal. For the chromatogram, paper strips are marked a t 4.5 and 8.5 cm. from the end to be immersed in the developing liquid. The sample to be chromatographed is applied at thr 8.5-cm. mark and allowed to dry. The frame is suspended from ring stands by its handles outside the tank and each strip is pierced first a t the lower or 4.5-em. mark, stretched taut, and then pierced by the top pin. With all the strips in position, the frame assen~blyis lowered into the tank until supported by the ears. Care must be taken to prcvent rontaniination of the strips by the tape while b h g mounted. The glass lid is set in position. When the solvent front has advanced sufficiently, the strips may be pulled off the pins selectively, or the entire frame may be removed from the t,ank and t h p strips dried, fiprsyetl, and developed while mounted.
I11 practicr, this aipparatua has greatly facilitated chromatographic procedures. I t is durable and permits the handling of large numbers of samples during the solvent separation phase of paper chromatography.
LITERATURE ClTED
Atkinsun, H. F., Nat7m, 162, 858 (1948). Consden, R., Gordon, A . H., and Martin. A . J P., Riochern. J , 38, 224 (1944). Hcftniann, Erich, Science, 111, 571 (1960). Loiigeneoker, W. H., ANAL.Cmm., 21, 1402 (1949). Imngenecker, W.H., Science, 107, 23 (1948). hfa, R. hi., and Fontaine, T. D., Ibid., 110, 232 (1949). Rockland, L. R., and Dunn, 31. S.,Ibid., 109, 559-40 (1949). Steward, F. C., Stepka, W., and Thompson,J. F., Ibid., 107, 451 (1948). Killiams, R. J., and Kirby, H., Ibid., 107, 481-3 (1948). Winsten, W.A., Ibid., 107, 605 (1948). Wolfson, W.Q., Cohn. C.. and Devaney, W. A., Ibid., 109, 541-3 (1949).
Improved 5-Mg. Rider for Ains worth Microchemical Balances LAWRENCE E. BROWN Southern Regional Research Laboratory, Kew Orleans, La.
RREGCLABITIES in the seating of the 5-nig. wire riders, customarily furnished with older Ainsworth microchemical balances Types F D and F D I , arc an important source of error. The magnitude of the seating error can be reduced by using a 0.5 mg. rider, but a sacrifice of convenience is entailed by the lower capacity of the beam. .4 5-nig. rider with a low seating error has been constructed of aluminum foil The essential feature of thiu rider is that it has a thin, btraight bcaring edge and can be brought to rest in the bottvni of the notch of the balance beam with ease and without undue nianipulation of the rider carrier. The rider is made of pure aluminum foil, 0.0036 to 0.004 inch thick. After a 2-inch (5-cm.) square of the foil is covered on both sides with cellulose tape, it is placed on a smooth hard surface and the eye of the rider is cut with a small sharp cork borer (No. 1) by a single light tap. The foil is then flattened between two pieces of plate glass and the irregularities in the circumference of the eye are removed ~ i t ah 3-mm. conical grinding wheel.
A-
The legs sliould be about 1-mm. wide and the angle with the bearing edge about looo. The cellulose tape is removed by soaking the formed rider in acetone. The legs are trimmed in length until the rider weighs about 5.1 mg. The final adjustment to exactly 5 mg. is made by dissolving some of the aluminum by immersion in 0.1 iV sodium hydroxide, which attacks microscopic burrs and imperfections preferentially. After final cleaning and drying, the rider is flattened by pressing between pieces of plate glass. I t is then ready for use.
Table I .
Standard Deviations of Observations Observed for Pan hrrestment and Rider,
Rider
+ Y
vu
Calculated for Rider Alone,
u* Y
5-mg. wire rider 1.9 1.7 5-mg. foil rider 1.3 1.0 0.9 0.5-mg. wire rider 1.2 a (x u ) = s observed for pan arrestment and rider. (z) = 8 observed for pan arrestment alone = 0.8 y. It = 30 observations in all cases. b y 8 calculated for rider seating alone a8 square root of differences of squares of (z g) and ( L ) .
+
5.5
m m.i 0.5
Figure 1.
o ~
0.5
+
mm.io.2
,ALUMINUM
;,lF
-
FOIL
m 2m o
2
Foil Rider
The coated foil is then placed on a hard smooth surface, such as a piece of late glass. The cutting edge of a rib-backed razor blade is re8uced to a length of 4.8 .t 0.2 mm. and used to cut the cross bar or bearing edge of the rider. The cutting edge of the blade is placed symmetrically about 0.5 mm. from the eye and the cut is made with a single tap on the back of the blade (Figure 1). Similarly, sharp blades are used to cut the insides and outsides of the legs, the outside shoulders, and the outside of the eye arc. The most critical points are the inside corners.
The performance of the foil rider compared with that of the riders supplied by the manufacturer, using an Ainsivorth Type FDI microchpmical balance, is indicated by the data given in Table I. The reading error on the optical lever scale was assumed to bc ncgligible. The standard deviation reported for the 5-mg. wire rider is for the best series of observations attained by the author after considerable experimentation in rider seating. Unless Ftiict care is used in seating, a much larger standard dcviatjoii occurs. The foil rider is adequately seated by a vertical drop of it from thc c;trrier Further manipulation, such as touching or rocking the seated ridrr with the tip of the carrier, results in l o w r precision. The difference found between the standard deviations of the 5-mg. foil and wire riders is statistically significant a t the 95% level. The other standard deviations observed are coilsidered typical mid indicate that the 5-mg. foil rider has ~1 seating error comparable to that of a conventional 0.5-mg. rider. RECEIVED July 6, 1950
