July 15, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
cipitation of an unknown mixture of barium salts should be treated with more reagent before it is discarded. It is necessary to neutralize the sample if much strong acid is present, since the precipitation of the barium salt is most complete in a neutral or slightly alkaline medium. Interference by aconitic acid requires a qualitative test for the absence of this material in the unknown mixture in order to determine the applicability of the method. The pink or blue coloration of acetic anhydride a t 100' C. (16) is of some value in detecting aconitic acid. The absence of this coloration indicates absence of aconitic acid. The rate of oxidation should be not greater than one drop of potassium permanganate solution in 10 seconds, since more rapid oxidation gives low results. The use of other oxidizing agents or more dilute permanganate was not found advantageous in the present procedure. For the smaller quantities in particular, the addition of manganous sulfate has proved useful, but this has not been essential for the successful application of the method within the sample range considered here. All the oxidative methods apply to the citrate ion; trimethyl citrate and citric triamide, for example, give no evidence of citrate content by the permanganate procedures unless they are first hydrolyzed.
285
ACKNOWLEDGMENT Acknowledgment is made of the helpful criticism of M. Kunitz and the technical assistance of B. Prytz. LITERATURECITED (1) (2) (3) (4) (5) (6) (7)
(8) (9) (10) (11) (12) (13) (14) (15) (16)
Camp, A. F., Ann. Missouri Botan. Gardens, 10, 213 (1923). DenigBs, D., Bull. SOC. chim., (3) 27, 1 (1902). Elsdon, G . D., and Lees, A., Analyst, 58, 328 (1933). Gowing-Scopes, L., Ibid., 38, 12 (1913). Hartmann, B. G., and Hillig, F., J. Assoc. Oflcial Agr. Chem., 11, 257 (1928). Kogan, A. I., 2.anal. Chem., 80, 112 (1930). Kuyper, A. C., J . Am. Chem. Soc., 55, 1722 (1933); Kuyper. A. C., and Mattill, H. A., J. Bid. Chem., 103, 51 (1933). McClure, W. B., Ibid., 53, 357 (1922). McClure, W. B., and Sauer, L. W., Am. J . Physiol., 62, 140 (1922). Nelson, E. K., J . Am. Chem. SOC.,50, 2006 (1928); 53, 1040 (1931). Nordbo, R., and Schersth, B., Skand. Arch. Physiol., 63, 124 (1932). &berg, O., Ibid., 62, 81 (1931). Rogina, B . , Arhiv. Hem. Farm., 6 , 119 (1932). Salant, W., and Wise, R. E., J. Bid. Chem., 28, 27 (1916). Tiiufel, K., and Mayr, F., 2.anal. Chem., 93, 1 (1933). Taylor, C. S., J. Chem. Soc., 115, 886 (1920).
RECEIVED February 6, 1934
A Large-Size Modified Soxhlet for Hot Extractions L. S. GRANT,JR., AND W. M. BILLING, Hercules Powder Company, Inc., Hopewell, Va.
T
HE need for a modified Soxhlet extractor intermediate
between the large-size Soxhlets ordinarily used for quantitative determinations and the very large extractors described by Cameron ( I ) , Drake and Spies (g), and McCay (4) but more refined than that described by Liston and Dehn (3) led the authors to design the extractor shown in Figure 1. This extractor is especially useful where the material is fibrous in structure or is to be given a hot extraction. The apparatus consists of three parts like the ordinary Soxhlet: the condenser A , the extractor body, C, and the receiving flask which fits at D. Condenser A consists of a 12-inch (30-cm.) Allihn condenser having the delivery tube bent and cut as shown. The flask (not shown) is a 2-liter flat-bottom flask having a No. 30 standard taper joint to fit at D. The body of the extractor, C, is 16 inches (40 cm.) in length (over-all) and carries a No. 50 standard taper joint, B, at the top and a No. 30 standard taper joint, D, at the bottom. The vapor tube, G, having a vent, V , at the top, carries the siphon tube E , fastened at points H t o ive it strength and protected by the shield, F. is vented at I and carries 6 or 8 holes, J , at the bottom. The body is 5 inches (12.5 cm.) in diameter and 10.5 inches (26 cm.) in height (exclusive of joints). Shield F is 2 inches (5 cm.) in diameter. The volume of liquid required to cause siphoning (extractor empty) is 1900 cc. This extractor overcomes the chief difficulty found in most Soxhlets-imperfect siphoningby the use of the large siphon shield F . This shield, besides protecting the siphon tube, acts as a reservoir so that the siphon is always in contact with liquid, the reservoir being so large that the solvent has considerable time to drain from the sample into the reservoir before the reservoir is emptied. For best results siphon tube E should be flattened a t the top and constricted a t the bottom as advised by Cameron
%
(1).
The fact that the vapor tube, G, passes through the liquid in the extractor means that only constant-boiling solvents, or those which have a very short boiling range, may be used because the liquid in the reservoir is always hot and refluxing will occur to such an extent that no extraction will take place if the solvent has a wide boiling range. However, by placing a chimney around the body of the extractor in such a manner that little heat is lost by radiation, extraction a t a few degrees below the boiling point of the solvent will take place when a constant-boiling solvent is used. Since siphoning is clean and rapid, very good hot extractions can be carried out in this manner. ' If low-boiling solvents are used and exceptionally rapid extractions are desired, i t would no doubt be advantageous to replace condenser A by one of the type described by Cameron (1). The extractor described above has been used mainly for the alcohol extraction of cotton linters, although other solvents have been employed. With this solvent excellent results have been obtained over a period of 6 months. ACKNOWLEDGMENT The authors wish to acknowledge the assistance of Otto Greiner & Company, of Newark, N. J., who made this extractor from Pyrex glass t o specifications. LITERATURE CITED (1) Cameron, A. E., IND.ENG.CHEM.,Anal. Ed., 4, 394 (1032). (2) Drake, N. L., and Spies, J. R., Ibid., 5,284 (1933). (3) Liston, T. R., and Dehn, W. M., Ibid., 5,, 306 (1933). (4) McCay, C. M., Ibid., 5, 213 (1933). RECEIVED March 29, 1934
