NOTES ON ANALYTICAL PROCEDURES Simple Automatic Control for Vacuum Systems 1. J. SPADARO, H. L. E. VIX, AND E. A. GASTROCK Southern Regional Research Laboratory, N e w Orleans, La.
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10
A
MODIFICATION of a commercial type of Cartesian manostat was so constructed as to bleed air to the system rather than throttle or modulate the vacuum supply. No electrical connections are required and the unit can thus be safely used with systems handling inflammable solvents under conditions where manostats as described by Munch (1) might be undesirable.
OPERATION.This modified manostat is illustrated in Figure 1. The valve unit is adjusted so that the rubber disk, E, rests on the orifice when the lower end of the wire is a proximately 1mm. from the top of the floatin bell. Stopcocks $and H remain open until the vacuum approacfes 10 mm. of the desired reduced pressure. B is then closed, while H remains partially open. The exact reduced pressure desired is obtained by adjusting the rubber disk on the wire. Functioning of the manostat is indicated by the continuous and rapid axial modulation of the valve unit. The operation is produced as follows: Since equal ressures must be maintained in the mercury-sealed chamber, If and in chamber J leading to the system, a change of pressure in J causes an upward or downward displacement of mercury in this chamber, thereby raising or lowering the floating bell, D. This in turn opens or closes orifice G, thus maintaining the equilibrium in the two chambers. A 2-mm. orifice controls reduced pressures down to 200 mm. of mercury (absolute) and a 1-mm. orifice controls pressures between 220 and 30 mm. The reduced pressure in a system can be automatically controlled to within *0.25 mm. of mercu by proper adjustments of the orifice, valve unit, and p e t c o g B. After pro er adjustments are made the pressure can be controlled for &n ingfinite period of time with no drifting of preasure within the system. Two modified manostats as described have been successfully used in the Southern Regional Research Laboratory for several months.
i
TO VACUUM PUMP
Figure 1. Modified Manostat A.
Maln body of manostat
B. Uowock
C. Sectlon for m e w r y seal D. Floating bell Valve unit conslats of adlustable rubber disk E attached to e rigld noncorrosive wire, F,kee to move erlelly throuclh'orlkcr G.
LITERATURE CITED
(1) Munoh,
'1
R.H.,J. Chem. Education, 9, 1275 (1932).
Absorption Spectrum of the Antimony TrichloridrErgosterol Reaction Product ALEXANDER MUELLER, Gelatin Products Corporation, Detroit, Mich. of 9122 and an value of 230.0 * 3% (average of 20 trials). Two additional absorption maxima were observed a t 322 mp and 510 mp with E!?m. values of 68.0 and 25.0, respectively. These measurements were performed on a sample of ergosterol which was shown to be 100% pure by a measurement of its ultraviolet absorption spectrum. The absorption maximum a t 393 mp was found to be stable for the period from 2 to 10 minutes following preparation of the antimony trichloride+rgosterol reaction product, making it possible to make very satisfactory quantitative measurements of its intensity. The absorption spectrum of the antimony trichloride-calciferol reaction product shows no absorption bands
D
URING the c o w of investigating the antimony trichloride absorption spectrum of vitamin D a t 500 mp, according to the method described by Nield, Russell, and Zimmerli (S),it was observed that solutions of the antimony trichloride reaction products of irradiated ergosterol exhibit an absorption band a t 393 mp aa well as at 500 mp. Further investigation of the absorption spectra of the antimony trichloride reaction products of pure samples of calciferol (vitamin De) obtained from Winthrop Chemical Co. and of pure ergosterol obtained from Standard Brands, Inc., indicates the absorption maximum a t 393 mp to be due to ergosterol. The absorption maximum at 393 mp is sharp and well defined, having a molecular extinction coefficient 214
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 to 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 to be constructed from materials readily available in most research laboratories and manufacturing plants.
FIGUR€ 2
I
D.... NGURC
1
Figures I, 9 , 3, and 4. Diagram of Laboratory Soxhlet Extractor, Showing Details of Construction and Dimensions
CONSTRUCTION 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 to the extraction chamber, B, to facilitate dismantling, is attached to A by means of an adapter, F. It is advisable to 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 to 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
