October 15, 1931
INDUSTRIAL AND ENGINEERING CHEMISTRY
It is evident that the volatilization method for fluorine as used a t present may give very unreliable results in the presence of precipitated silica and of silicates that are decomposed by sulfuric acid. Literature Cited (1) Casares, Ann. soc. e s p a l 2 . f h .iu%m.(tec.), 27,290 (1929). (2) Daniel, Z.anoyg. Chem., 38,290 (1904). 22, 1392 (1930). (3) Hill, Jacob, Alexander, and Marshall, LND. ENG.CHEM.,
373
(4) Hillebrand and Lundell, “Applied Inorganic Analysis,’’ p. 600, ~ i l e y ,
1929.
(5) Jacob, Hill, and Holmes, Colloid Symposium Annual, Vol. VII, p. 195 (1930). (6) Jacob and Reynolds, J . Assocn ORiciaZ Agr. Chem., 11, 237 (1928). (7) Miehr, Koch, and Kratzert, Z.angccs. Chem., 43,250 (1930). (8) Patrick, Fraser, and Rush, J . Phys. Chem., 31, 1511 (1927). (9) Reynolds and Jacob, IND. ENG.CHEM.,Anal. Ed., 3, 366 (1931). (10) Reynolds, Jacob, and Hill, IND. END.CHEM.,21, 1253 (1929). (11) Reynolds, Ross, and Jacob, J . Assocn. OficiaZ Agu. Chem., 11,225 (1928). 9, 1116 (1917). (12) Wagner and Ross, J . IND. ENG.CHEM.,
Stillhead for Laboratory Columns’j2 E. B. Kester and R. Andrews PITTSBURGH EXPERIMENT STATION, U.S. BUREAUOF MINES,PITTSBURGH, PA.
HE most satisfactory type of stillhead for column fractionation in the laboratory is one simple in construction, attachable to the column without rubber or cork connections, suitable for both low- and high-boiling liquids, and designed to minimize hold-up. Also, it should permit the operator to establish a reflux ratio commensurate with the sharpness of fractionation desired. Column elongation should not produce severe mechanical strains. The stillhead shown in Figure 1made of Pyrex glass, combines most of these qualities. For attaching to the column, it is provided with a standard interchangeable ground-glass joint 25 mm. in diameter a t the end. Immediately above is attached a drip point for the purpose of throwing the descending condensate to the center of the column so that it may distribute itself over the packing. Otherwise, the liquid would merely run down the sides and come in contact with very little of the ascending vapor. The heavy part of the stillhead-that is, the condenser-is, when installed, in line with the column itself. This arrangement is almost a necessity in a long glass assembly of this kind where a rigid type of connection is employed, because of the upward expansion that is likely to occur. In the present instance, such expansion merely lifts the stillhead with it and produces no beam action whatever. The only horizontal appendage carried is a light side arm which can be supported by a brace integral with that used for the condenser. Other details of construction and operation of this stillhead can best be understood by referring to the diagram. The ascending vapors rise through port A and on up through ports B into the reflux condenser. The liquid formed runs down through drip point C and into the off-take as far as cock D, which is kept closed until equilibrium has been established. An overflow of condensate through E is very quickly produced, which proceeds into the column by way of drip point J . When the low-boiling constituent has concentrated in the head, as indicated by the thermometer a t the top of the column reaching a minimum, valve D can be cracked to a point where the desired drop ratio exists between C and G. H i s a cooling device to prevent loss through evaporation by reducing the temperature of the liquids that pass through D. It need only be about 6 inches (15.24 cm.) long and of slim construction to avoid bulkiness and undue weight. Incidentally, its jacket may be in series with the condenser jacket. Cock D is best equipped with a hollow key if high-boiling liquids are to be fractionated, as the possibility of its breaking from heat strains in contrast with the ordinary solid key is very little. Slots filed on either side of the aperture a t both ends are of assistance in adjusting the reflux ratio properly.
T
Received May 19, 1931 by permission of the Director, U. S. Bureau of Mines. (Not subject to copyright )
Capillary tubing of 2-mm. bore should be used in the off-take as far as D to minimize hold-up, but between D and G standard tubing is satisfactory. Once installed and the clamps adjusted to eliminate strains completely, a stillhead of this type can be used to good advantage in the fractionation of corrosive or non-corrosive liquids boiling over wide temperature ranges. One in operation in this laboratory for the fractionation of tar distillates and high-boiling tar acids is proving quite satisfactory. The standard ground-glass joint is an ideal type of connection and can also be successfully used for attaching flasks to the base of the column. Where phenols have to be distilled, for example, it is of great value, as cork and rubber are eaten away very quickly with the result that the distillate becomes contaminated.
1It
1
* Published
Figure 1-Stillhead
for Laboratory Column
