ANALYTICAL EDITION
March, 1946
in the 300 to 400 mp region. These results indicate that a measurement of the absorption maximum a t 393 mp of the antimony trichloride reaction product of irradiated ergosterol should offer a satisfactory method for the quantitative determination of the ergosterol present. The absorption maxima at 322 and 510 mp are of low intensity and not satisfactory for quantitative measurement, but are helpful in the qualitative identification of ergosterol. A more detailed report on a spectrophotometric method for the quantitative determination of ergosterol in the presence of vitamins D, cholesterol, and 7-dehydrocholesterol based upon the observation is reported in this issue (8).
215
The spectrophotometric measurements were made with a Beckman Model DU spectrophotometer and incandescent light source. The details of the procedure used in carrying out the antimony trichloride reaction are the same as described by Ewing, Kingsley, Brown, and Emmett (1). LITERATURE CITED (1) Ewing, D. T., Kingsley, G . V., Brown, R. A., and Emmett, A. D.,
IND. ENQ.CHEM.,ANAL.ED.,15,301 (1943).
(2) Lamb, F. W., Mueller, A., andBeach, G . W., Ibid., 18,187(1946). (3) Nield, C. H.,Russell, W. C., and Zimmerli. A,, J. Biol. Chem.,
136,73 (1940).
Large-Size Laboratory Soxhlet Extractor RALPH SALKIN AND IRVING ALLAN KAYE' Research Laboratory, Endo Products, Inc. Richmond Hill 18, N. Y.
IN AN
investigation involving the extraction of plant lipids, the need arose for an apparatus which could efficiently extract 25 t o 30 pounds of finely ground milkweed seeds. Although numerous extractors of different capacities have been described in the chemical literature, it was felt that the type described by 1
Present address, Brooklyn College, Brooklyn, N. Y.
Rapp, Woodmansee and McHargue (1) was most satisfactory. This extractor can be used for a Soxhlet-type of extraction with hot solvent. I n preparing a smaller model of this apparatus, several simplifications in fabrication were introduced, enabling it t o be constructed from materials readily available in most research laboratories and manufacturing plants. CONSTRUCTION
FIGUR€ 2
I
D.... NGURC
1
Figures I, 9 , 3, and 4. Diagram of Laboratory Soxhlet Extractor, Showing Details of Construction and Dimensions
OF EXTRACTOR
The extractor is shown in Figure 1. The boiler, A , consists of a 5-gallon wide-mouthed Pyrex bottle set in a steam bath, D, of appropriate size. The vapor tube, E, made of 1.0-inch brass pipe and fittings, with a union adjacent t o the extraction chamber, B, to facilitate dismantling, is attached t o A by means of a n adapter, F. It is advisable t o lag- the vapor tube,. E ., with 1.0-inch asbestos pipe covering. The upper part of the adaptor, F1, consists of a &inch sauare (Fisure 2) of 0.25inch sheet brass ha&g a 'hoie tapped with a 1-inch I.P.S. It consists of a hole for the siphon tube, G and four corner holes for bolts. The bottom half of the adaptor, F2,is made of I-inch wood, the inside hole being lined with sheet cork. The details are given in the drawing. A vaportight seal is obtained by use of either an asbestos or sheet cork gasket in conjunction with any vegetable-base pipe-joint compound. A sound cork, in conjunction with the pipe-joint compound, may be substituted for the adaptor. The siphon tube, G, is made of 0.31-inch outside diameter copper tubing which is soldered into F1, and coupled with the extraction chamber, B , by means of a 0.125-inch union, GI. The diameter of G for the particular application was found to be important. Tubing of larger diameter was apparently inadequake t o provide proper siphon action, the solvent merely spilling over as rapidly as it was condensed. The optimum diameter a p pears to depend on several operational vanablese.g., rate of distillation, temperature of condensate, etc. A sharp bend is important in facilitating siphoning. B is made from a sheet-metal batch can of about 12-gallon capacity, the type used in s h i p ping bulk chemicals. It has a beaded top edge, B1 (Figure 3), and recessed cover, Bs, containing a gasket. The cover and can were coupled in a solvent-tight seal by means of a metal ring (furnished as an integral part of the can), B3. The best type of gasket was found to, be JohnsManville style No. 322*/,,inch packmg. After repeated use, i t showed no signs of wear. B is provided with an internal steam coil, B,, made of 0.31-inch outside diameter copper tubing (about 6 to 7 coils are adequate). This coil serves
216
INDUSTRIAL A N D ENGINEERING CHEMISTRY
a dual purpose, enabling the extraction to be performed at elevated temperatures and facilitating the drying of the extracted material in the final recovery of the solvent. The tubing is attached to B by inserting two 1-inch lengths of 0.5-inch running thread through holes reamed in the side of the can and securing them in place by lock-nuts and fiber washers of appropriate size. The precoiled tubing is placed in the extraction chamber, the ends of the tubing passing through the nipples and being held in place inside the nipples by asbestos tape. Solder is then poured into the remaining space. The openings for the siphon tube on the bottom of the can and for the condenser on t h e top of the can are made in a similar manner, except that no solder is needed. A breather tube, to facilitate siphoning, is made of Gshaped copper tubing 0.25 inch in outside diameter, which extends from the siphon tube along the bottom and up the side of the can above the siphoning level. The material to be extracted is placed in a strong canvas bag with a pull-cord top. The bag fits snugly into the can and is placed on a rircular piece of 1.0-inch mesh which is raised slightly from the bottom of the can to facilitate siphoning. I n constructing the stand, I, for the extraction chamber, 0.5inch pipe is wed. The condenser coil, C1 is made of 0.25-inch outside diameter 'copper tuhing tightly wound, the ends projecting through a 2.0inch brass plug, Ct, and soldered in place. Cn IS screwed into a 2.0-inch tee. C,. which is at,tached t o a 24-inch length of 2.0-inch _ . pipe. The lhtt"& i s attached to the extraction chamber by means of a 2.0-inch brass coupling, Cd. To adapt this apparatus for downward distillation, C is dismantled, a 2.0-inch street ell, CS(Figure 4), is screwed into C,, a
Vol. 18, No. 3
2.0-inch nipple is screwed into the street ell, and the condenser is screwed to this nipple as shown. To facilitate collection of the recovered solvent, the pipe size of the condenser is reduced t o 0.75 inch by means of a reducing coupling and a 6.0-inch nipple CS,which passes through a sound stopper into a wide-mouthed receiver. This stopper also bears a n L-shaped piece of tubing, H, as illustrated. If it is desired t o dry the extracted material completely and remove all but traces of solvent from the extracted oil, steam may be passed through the coil of the extractor chamber and through the steam bath, D. A capillary may be inserted through the tee at the top of the vapor tube, E, and gentle suction applied at H for more efficient removal of solvent. If the material t o be extracted is intended for food use and copper and brass may lead t o possible future deterioration, block tin t,ubing may be substituted for copper and Monel fittings used in place of brass. CONCLUSION
The apparatus described is efficient, giving values that closely approximate quantitative determinations in the conventional all-glass apparatus. The over-all solvent recovery is good, varying from 80 to ROOjo, ,dependent on the solvent. LITERATURE CITED
(1) Rapp, K. E.,Woodmansee, C. W., and McHargue, J. S., IND. ENQ.CHEM..ANAL.ED., 15, 351 (1943).
BOOK REVIEWS spectrographic analysis of zinc and zinc alloys for die Casting. The first paper (32 pages) deals with the polarographic determination of impurities. The balance of the text reports on the use of spectrographic methods involving three different types of excitation. The In this 120-page booklet, the author discusses the application of simple condensed spark is employed for the determination of alloying colorimetry in its broader sense to the problems of chemiutry. In constituents (aluminum, copper, and magnesium). An intermittent addition to the chemist's common concept of colorimetry as the alternating current arc of high sensitivity and reproducibility is measurement of the concentration of a colored constituent, or a condescribed for the determination of impurities in samples which are stituent which can be transformed into a colored form, the measemployed as solid electrodes. The concluding paper describes an urement and use of surh color quality factors as the dominant wave oxiddirect current arc method which is based on solution of the metal. length, purity, and brightness are described in some detail. The distinguishing features and limitations of typical commerThe polarographic section disscusses theoretical aspects and pays cially available instruments are briefly discussed. Recognition of particular attention to the behavior of tin, copper, and iron. The discussions of the behavior of tin and of the methods for removing the limitations of instrumentation has prompted the author to make interferences, particularly copper, are valuable. a very timely plea for more uniformity in the presentation of data The papers dealing with the spectrographic method describe in for publication, especially for the inclusion of information necessary to the critical evaluation of the data. The author includes a very detail the aspects familiar to all spectrographers. Factors affecting sensitivity and accuracy, such as types of and variation in excitation brief section on the interpretation of transmission and reflectance conditions, the influence of certain elements on the radiations due to curves in terms of the corresponding I.C.I. tristimulus coe5cient0, luminance, dominant wave length, and purity. another, the types and shapes of electrodes, the choice of analytical This publication should hold considerable interest for chemists and internal standard lines, etc., have been studied. The last paper planning colorimetric studies; it should aid the experienced in obalso gives an excellent description of plate calibration techniques by two methods, one based on the Schwarsschild law and the other emtaining even more useful and valuable information from available equipment; and it should serve as a guide in the preparation of mateploying a step filter. The book lacks su5cient literature references, but will prove useful rial for publication in the chemical literature. 0. R. ALEXANDER as a practical guide in the analysis of the specific materials to which the methods have been applied. The experiences which are reported when combined with more recent developments should result in modifications which will improve the convenience and accuracies of the apPolarographic and Spectrographic Analysis of High Purity Zinc and plications. Steps in this direction would appear to be (1) in the Zinc Alloys for Die Casting. A . S. Nickelson and J. E B . Randles. polarographic method, the incorporation of Lingane's method for reix f 117 pages. H. M. Stationery O5ce, London, 1945. Price, moving copper interference by eIectrolytic separation a t controlled 5 8. potential with a mercury cathode, and (2) in certain spectrographic applications, the use of the high-voltage alternating current arc comThis book, which is composed of four papers, gives a detailed acbined with photometry based on plate calibration and background count of the experimental work carried out from 1941 to 1944 by the correction as employed in American practice. British Standards Institution Panels in connection with its commisJ. CHOLAH sion to prepare and recommend methods for the polarographic and Colorimetry for Chemists. M. G. Mdlon. 120 pages. The G . Frederick Smith Chcmical Co., 867 McKinley Ave., Columbus, Ohio, 1945. Price, heavy board back, $1.00; paper cover, free.
