Plant Sampling Technique. Additional tests were made t o determine what difficulties would be encountered in taking samples from the operating unit. The final apparatus used is shown in Figure 3. A 2-liter bottle packed with glass woo1 was inserted before the train when a gas containing moderate quantities of entrainment was being sampled. A Millipore filt.er WBS used as a final cleanup device to eliminate acid entrainment from getting into the gas sample.
LITERATURE CITED
(1) Gaillard, D. P., Ind. Eng. Chem. 11, 745 (1919). (2) Gill, W. E., Am. Znd. Hyg. Assoc. J. 21, 92 (1960). (3) Graham, H. G., Jr., Lyom, V. E., Faucett, H. L., Chem. Eng. Progr. 60, 77 (1964).
(7) Thomas, M. D., MacLeod, J. A.,
Robbins, R. C., Goettleman, R. C., Eldridge, R. W., Rogers, L. H., Ibid.,
28, 1810 (1956).
H. L. FAUCETT T. C. MCRIGHT H. G. GRAHAM, JR.
(4) Johnson, C. L., ANAL. CHEM.24,
Tennessee Valley Authority Muscle Shoals, Ala.
1572 (1952). (5) Saltzman, B. E., Zbid., 26, 1949 (1954). (6) Salt,zman, B. E., Ibid., 33, 1100 (1961).
Presented at the Southeast-Southwest Regional Meeting, ACS, Memphis, Tenn., December 1965.
Extraction in a Beaker Evan Morgan, Metallurgical Laboratories, Reynolds Metals Co., Richmond, Va.
THE DETERMIXATION of trace amounts of lead, one is confronted with a need for a satisfactory means of separating the lead from the ions which may be present. Lead can be completely extracted from a slightly basic solution, containing citrate or tartrate to prevent the precipitation of foreign metal hydroxides, by a small excess of dithizone in either carbon tetrachloride or chloroform (1, 3). With chloroform the optimum pH range in citratecyanide medium has been reported as 8.5-11. The simplest type of liquid-liquid extraction is batch extraction where the solute is extracted from one immiscible layer by shaking the two layers until equilibrium is attained. Then the layers are allowed to settle and are separated. Continuous extractions are particularly applicable when the distribution ratio is relatively small so that a large number of batch extractions would normally be necessary to effect quantitative separations. A continuous extraction device applicable to the separation of lead would require stripping the lead from the extracting solvent and passing it continuously through the solution being extracted. Such an extractor, designed specifically for the continuous extraction of metals using chelating agents is that of Meinke and Anderson ( 2 ) . A less expensive device has been considered which may be described as a compartmented beaker. I n this beaker it is possible to float two aqueous soluOR
tions on an organic liquid and in so doing, extract the solute from one of the aqueous phases into the organic phase, and in turn strip the solute from the organic phase with the second aqueous solution. Two methods of compartmenting a beaker have been considered. First, using a flat glass plate sealed to the sides of the beaker, and second, with a concentric glass cylinder supported a t the top by glass rods. The dividing member is short of the bottom of the beaker by approximately 1.5 cm. Stirring by either a magnetic stirring bar or an overhead motor and glass rod are possible. EXPERIMENTAL
In this laboratory, a beaker of the second type has been constructed. A 7-cm. section of 41-mm. 0.d. glass tubing is supported concentrically in a 250-ml. beaker by 3 pieces of glass rod. The 1.5-cm. clearance (distance from bottom of tubing to bottom of beaker) allows a l - 5 / & in. magnetic stirring bar to be used without hindrance. In use, the beaker is filled to a depth of approximately 3 cm. with 0.005% dithisone in chloroform solution. This provides an effective seal between the two compartments. Into one of the compartments is placed a slightly basic solution of the lead to be extracted. The other compartment contains a slightly acidic (1 :100 nitric acid) stripping solution. The motor speed is adjusted for gentle stirring, and allowed
to run for the necessary time to move the lead to the acidic solution. Table I gives the results of a typical test. Twenty micrograms of lead in 25 ml. of 1: 100 ammonium hydroxide was placed in the outer chamber; 20 ml. of 1 : l O O nitric acid was placed in the center chamber. At the end of each time period, 10 ml. of the acidic solution was removed and analyzed for lead, and 10 ml. of 1 : l O O nitric acid added to replenish the stripping solution.
Table I.
Agitation, minutes 30 60 90 120 150
Data for a Typical Extraction
Lead transferred, pg. 8.2 7.9 2.4 1.8 0.4
Total lead transferred, pg. 8.2 16.1 18.5
20.3 20.7
Percentage extracted 40 78 89 98 100
Studies on this device will continue to determine whether the technique is applicable to the separation of lead from a multi-component alloy. LITERATURE CITED
(1) Mathre, 0. B., Sandell, E. B., Talanta 11, 295 (1964). (2) Meinke, W. W., Anderson, R. E., ANAL.CHEM.24, 708 (1952). (3) Sandell, E. B., “Colorimetric Determination of T r a m of Metals,” 3rd. ed., Interscience, New York, 1959.
VOL. 38, NO. 8, JULY 1966
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