288
ANALYTICAL CHEMISTRY
once the sulfuric acid is added, I n practice, reservoir A is filled with more than sufficient concentrated sulfuric acid for the experiment. By gentle suction, a n aliquot volume of sulfuric acid can be.transferred t o the dropping funnel, B , from the storage reservoir. Stopcock C controls the rate of sulfuric acid addition to the chloride in the reaction vessel, The rate of hydrogen chloride evolution is indicated b y the bubbler, G, containing concentrated sulfuric acid. The latter thus serves for the preliminary drying of the hydrogen chloride. The three towers, H , are packed with Drierite and glass wool. The stock solution receiving the anhydrous hydrogen chloride connects in at the exit of train J. A novel feature is that the spent reaction mixture can be siphoned from chamber F through outlet E by applying gentle suction. Preparation for a new charge can thus be effected with very little labor and a minimum of hazard. I n addition, by maintaining the bulk of the sulfuric acid in A , the danger of a serious acid spill through failure of stopcock C is effectively avoided. A safety tube, consisting of a mercury bubbler open t o the atmosphere, is used in practice between F and G . I n this laboratory the apparatus was designed to handle sodium chloride charges of 5 to 50 grams. The apparatus was all borosilicate glass. lressels A , F , and G were 45 mm. in diameter and 30 cm. in length, and H was 25 mm. in diameter and 60 cm. in length, Reservoir B vas 100 ml., and side arm D was a 24/ 40 standard taper joint. All the other tubing was 6 mm. in diameter. The generator operates equally well with concentrated hydrochloric acid as with a solid chloride for the reaction chargc. From chamber F t o exit J , escape of the hydrogen chloride to the atmosphere is impossible, for the apparatus is a continuous glass unit. Once the storage reservoir, A , has been charged, all transfers of the sulfuric acid, and the spent reaction mixture can be effected by siphoning action. ACK5OB LEDGMENT
This apparatus was developed in the course of work supported hy the Office of Scientific Research, Air Research and Development Command, under Contract AF lS(600)-333.
Trough for Use in Descending Paper Chromatography John F. Thompson and Maurice V. Marion, U. S. Plant, Soil, and Nutrition Laboratory, Agricultural Research Service, Ithaca, N. Y.
iron troughs have been recommended (6) for use E in descending tLvo-directional paper chromatography. However, it has been found that in using these with acidic solNAMELED
vents-e.g., butanol and acetic acid (5)-the enamel chipped off, exposing the metal surface t o the paper and solvent. This is undesirable in quantitative analysis of amino acids, because metals form complexes with amino acids which do not chromatograph well and do not react with ninhydrin (3). Metals also catalyze the oxidation of phenol, forming products which deaminate amino acids ( 8 ) . Stainless steel troughs ( 1 ) are unsatisfactory for this reason. Another type of trough is made of glass tubing (S, 4 ) , but this is fragile and requires a rigid suppori over the entire lrngth. A more satisfactory troiigh is made from borosilicate glass pipe with a wall thickness of 4 mm., 42 mm. in outside diameter and 26 inches long (fabricated by Scientific Glass Apparatus Co., Bloomfield, N. J.). This trough is strong and rigid and requires no auxiliary support. There has been no breakage in two years of intensive use. I n addition t o resistance t o acidic solvents, the glass troughs hold larger quantities of solvent than the enameled ones (6) (300 ml. 2,s. 200 ml. maximum capacity), and are less expensive. The principal disadvantage of the glass trough lies in the fact that the glass supporting rods must be mounted separately. This problem has been solved by making one rack for all supporting rods in a cabinet. Glass rods are fastened in a paraffined wooden support at each end, just beyond the ends of the trough. The support is positioned with four wooden dowel pins which fit into holes in the rack, automatically aligning rods over the edges of the troughs. By clipping the developed papers to the
glass rods, all chromatograms in a cabinet can be removed simultaneously by lifting out the whole rack. The solvents are then evaporated from the paper in this position. LITERATURE CITED
(1) Benhon, d.-4., Bassham, G. A., Calvin, hl., Goodall, T. C., Hass, V. -4., and Stepka, W., Atomic Energy Commission Report
UCRL-363. Vol. 11, Chap. I. ( 2 ) Clarke. H. T., in “Organic Chemistry,” ed. by H. Gilman, Tol.
11, Chap. 14, Wiley, Sew York, 1938. (3) Consden, K.,Gordon, A. H., and Martin, A . J. P., Biochem. J . 38, 224(1944). (4) Longenecker, W. H., Science 107, 23(1948). (5) Partridge, S.AI., Biochem. J . 42, 238(1948). (6) Steward, F. C., Stepka, W., and Thompson, J. F., Sciericc 107,
451 (1948).
Packing Adsorbents in Chromatographic Columns Wallace L. Ronkin, Cancer Research Laboratory, Jennie Edrnundson Memorial Hospital, Council Bluffs, Iowa
u*
of packing is a necessity for clear separation of constituents on a chromatographic column (4,5, 8 ) , but some recent references have been somewhat vague on the best method of packing a column ( 1 , 2, 6, 7 ) . Engineers in the field of soil mechanics have shown that the densest mass of a given group of particles is obtained when those particles are compacted in a confined space in a “saturated” condition-Le., there are no air voids present (3). Maximum compaction of sand in a container of water can be obtained by tapping the sides of the container while the water is flowing slowly downward. Any upward movement of the water causes disturbance of the compacted sand. The following method of preparing a chromatographic column is therefore recommended. The adsorbent (Florisil, silica, etc.) should be slurried with the first solvent t o be used in the separation. The column is half filled with the solvent, and the slurry is poured into the column; the clear solvent is drained from the bottom if necessary. After all of the adsorbent has been transferred to the column, the solvent is allowed to drain a t some intermediate rate (0.1 to 1.0 ml. per minute), while the side of the tube is firmly tapped with a rubber mallet or a large rubber stopper. Some liquid should always be present above the top of the adsorbent to avoid entrapment of air. By this method of column preparation, the maximum packing can be achieved m-ith little lowering of the flow rate (provided adsorbents larger than 200-mesh size are used). Because no air is present, there is no air-liquid interfacial tension, and flow rates of 1 or 2 ml. per minute are easily attained. No pressure, suction, or pressing with a rod is necessary, and the maximum surface arpa of contact between adsorbent and solvent is achieved. YrFoRwTY
ACKNOW’LEDG.1IEZIT
This work was conducted x i t h the support of the Iowa Division of the ilnierican Cancer Society. LITERATURE CITED
(1) Carlton, J. K., and Bradbury, W. C., ANAL.CHEM.27, 67 (1955) (2) Cassidy, H. G., “Adsorption and Chromatography,” vol. T’, p. 240, of “Technique of Organic Chemistry,” ed. by Weissberger, A., Interscience, New York, 1951. (3) Gizienski, S.F., private communication. (4) Green, K.,and Schechter, h l . S., ANAL.CHEM.27, 1261 (1955). ( 5 ) Haines, W. J., and Karnemaat, J. N.,“Methods of Biochemical Analysis,” vol. I, p. 178, ed. by Glick, D., Interscience, NenYork - - - - - , 1954 (6) Hough, L., Ibid., vol. I, p. 231.
( 7 ) Malmberg, E. W., A N ~ L CHEM. . 27, 840 (1955). (8) Scott, R. W., Ibid.,27, 367 (1955).
