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INDUSTRIAL AND ENGINEERING CHEMISTRY
room temperature and a t pressures varying from a few millimeters of mercury absolute to several pounds per square inch gage. I t is suitable for the analogous operations of absorption and extraction and may also be used as a reaction tube. In the latter case, the reaction tube should be provided with an additional heating element. While the design of this column is best suited for operations above room temperature, it may also be used for low-temperature work where it is necessary to observe the column action. I n this operation, the cooling fluid would be circulated in the annular space between the 55- and 70-mm. jacket tubes. If the fluid was introduced several inches below the upper disk, only the lower end of the jacket would have to be sealed by a gasket. The still head shown in the figure is a composite of several types used by the authors. The thermocouple well extending down through the packing is useful where the temperature is a criterion of the product compositions. While the thermocouple well will decrease the efficiency of the packing, this is in many cases compensated for by the gain in operability of the column. It enables the optimum reflux ratio to be set with a minimum of trial and error and the future course of batch distillations to be predicted without frequent readings of the temperature. The vapor sampling line, 0, is used where it is necessary to maintain a high reflux ratio and low holdup, as in the case of analytical distillations. Reflux ratios of 20/1 ( O / P ) are readily
Vol. 16, No. 10
and accurately obtained by adjusting the stopcock and then applying a slight pressure to the column (or vacuum to the receiver). The take-off rate is closely proportional to the square root of the pressure applied. Other advantages of vapor sampling are that it minimize8 contamination of the sample by the stopcock grease and allows accurate sampling of distillates which give two liquid phases upon condensation. A simple method of attaching accessories to the still head ie illustratecLin the figure for operation a t total reflux with product holdup. The receiver is suspended in a clamp, so that line L may be connected to it. The receiver is then rotated on its own axis until line K may be connected. The connecting lines have sufficient flexibility to allow them to be slid emily.into place at the same time providing tight seals for vacuum work. The connections illustrated are pieces of rolled rubber tubing to provide flexibility. In the case of high-boilin organic solvents, standardtaper joints may be used a t points and K. The capacity of the receiver may be varied by the use of return lines of different lengths. This same receiver, by closing the stopcock in return line K , may be used for automatically discontinuing the removal of product in batch distillations.
k
The applications of this still head to the various types of azeotropic distillations with two-phase condensate are similar to the above and do not require description.
Method For Detecting Inadequately Heated Soybean Oil M e a l C. D. CASKEY,
JR.,
AND
FRANCES C. KNAPP
Southern States Laboratories, Baltimore, Md.
Editor's Note. Since receipt of this p p e r , a subcommittoe of the Animal Nutrition Committee of the National Research Council has been appointed to study tests which might be applied to soybean oil meals to indicate the degree of heat treatment and to correlate i t with biological efficiency. The committee is carrying on collaborative work with additional samples in order to check further the validity of the urease test.
Since the over-all processing conditions of temperature, time, and moisture content favorable for protein denaturation would also be favorable for the inactivation of enzymes, a test based upon the enzymatic activity of the finished product was indicated. Urease was selected because of its unusually high concentration in soybeans and the ease with which its presence can
T
Table
HE high nutritive value of soybean oil meal for poultry
and swine depends considerably upon the heat treatment used in its preparation. Adequate heat treatment improves the biological value .of the proteins (8, 3, 4) and simultaneously inactivates the enzymes present (6). The enzyme lipoxidase if left active in the meal could readily cause the destruction of vitamin A or its precursors with which it comes in contact in the digestive tract of animals. The contemplated use of urea in feed mixtures for ruminants makes it important that the soybean oil meal used in such mixtures be heated sufficiently to inactivate urease. Mixtures of inadequately heated soybean meals or raw soybeans and urea develop the highly characteristic odor of ammonia and, hence, become unpalatable. It hm been reported by Bird and co-workers ( 1 ) that commercially produced meals differ markedly in their nutritive values when used as the principal source of protein in the chick ration. Some of the poor results obtained were attributed to the use of insufficiently heated meals. With the enormously increased production of soybeans and their subsequent conversion into meal by plants having no previous experience with this commodity, the need for a rapid test for determining adequacy of heat treatment is apparent.
1. Growth Response and Results of Tests on Samples of M e a l Receiving Different Heat Treatments Average Chick Weight at 9 Weeks. Grams0
Treatment
Results on Test Solution, PH
Experiment I Raw beans 143O F 11.6 minutq 173' F:: 16.5 minutes 175' F., 105 minutes 217' F., 42 minutes Solvent meal Hydraulic meal B
476 528 586 572 669 798 637
8.9 8.8 8.6 8.7 7.6 7.1 8.9
664 728 733 784
8.4 7.1 7.1 7.1
317 494 483 443 494
8.6 7.1 7.1 7.1 7.1
Experiment I1
Experiment Raw meal Autoclaved 2.5 minutes at 20 pounds Autoclaved 7.5 minutes at 20 pounds Autoclaved 12.5 minutes at 20 pounds Autoclaved 60 minutes at 5 pounds 5
b e
Growth data from ( 1 ) . Producer's designation. Weights given for 7th week.
IIIC
ANALYTICAL EDITION
October, 1944 Table II. Date May 27
Dropping Funnel
Precision of Test Results on Test Solution, pH 7.59 7.68 7.72 7.55 7.59
August 2
August 9
.4ugust 10 August 11
be detected. The following test based upon Sumner's (5) qualitative test for this enzyme was devised.
KENNETH A. KOBE' University of Washington, Seattle, Wash.
I
N WORK for which a steam-jacketed dropping funnel is required the ordinary type is unsatisfactory because of difficulty in manipulating the stopcock to give a regulated flow of liquid from the funnel. I t is also unsatisfactory where the liauid contained in the funnel must not dissolve stopcock grease.
PROCEDURE
To approximately 10 ml. of 0.05 M phosphate buffer solution of pH 7.0 containing 0.3 gram of urea and 2 drops of 0.1% phenol red solution is added 0.2 gram of the meal under test. The mixture is allowed to stand with occasional shaking a t 25' to 30' C. for 30 minutes. If sufficient urease is present to cause an increase in the p H of the solution of one unit as indicated by a change in color to deep red, the meal has not been heated sufficiently. Adequately heated meals produce little or no color change. If the presence of alkaline salts is suspected, a blank should be run, using a sample of the meal which has been inactivated by heating a t 135' C. for 30 minutes.
Table Ill.
Results Obtained on Samples of Commercially Produced Meals Samples Results on TYPE Brand Tested Test Solution Hydraulic A 7 pH 8.3 12 pH 8.5 Hydraulic R Hydraulic C D E 16 No change Solvent H, L 5 No change A , F, G,I, J 45 No change Expeller
RESULTS
I n order to correlate the chemical test with actual feeding value, samples of meals of known history were secured through the courtesy of H.'R. Bird of the Maryland Experiment Station. The results obtained using this test on those samples are given in Table I. The readings are given in terms of pH values instead of color change because of the greater accuracy obtainable. In general, those meals which gave the poorest growth response exhibited the highest urease activity. Unfortunately, the test cannot be used to indicate excessive heat treatment. -4sample giving intermediate values was selected for periodic testing in order to determine the reproducibility of results. The results given in Table I1 were obtained with a Beckman p H meter and indicate a variation of not more than 0.2 pH unit, which is well within the range of the colorimetric method. The results given in Table I11 show that some meals produced by the hydraulic process on the market today are insufficiently heated. SUMMARY
A simple rapid test based upon the urease activity of the soybean oil meal has been devised to detect inadequately heated soybean meals. LITERATURE CITED
(1) Bird, H. R., and Burkhardt, G J., Maryland Agr. Expt. Sta., Bull. A27 (1943) (2) Hayward, J. W., Steenhock, H., and Bohstedt, G., J. Nutrition,
11, 219 (1936). (3) Osborne, T.B , a n d Mendel, L. B., J . B i d . Chen., 32,369 (1917). (4) Robison, W.L., Ohio Agr. Expt. Sta., Bull. 452 (1930). (5) Sumner, J B., and Somers. C. F., "Laboratory Experiments in Biological Chemistry", New York, Academic Press, 1944. (6) Sumner, R . J., and Tressler, D. K., IND.EXG.CHEM.,35, 921 (1943).
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\ A
\ L
The figure shows a dropping funnel which does not p o s s e s s t h e s e difficulties. This funnel contains an internal ground joint, A . The liquid in the bulb flows down a narrow groove, B , in the outer wall and through a 2mm. hole, C, in the hollow center plug (see enlarged cross-sectional view). This tapers down t o a dropping point, D , which shows the rate of flow through opening C. On the upper lip of the top of the funnel is a small point of glass, F , and the handle, E, is placed in such a position that E and F are in the vertical plane with B and C when the hole is in the open position. The entire funnel and ground joint can be placed in a steam or hot water bath, the ground seat needs no lubricant, for the contained liquid will so act, and if any liquid leaks through the joint it can drop only into the reaction flask. ACKNOWLEDGMENT
The author wishes to thank Ray Newberry, university glassblower, for his work in constructing this apparatus. 1 Present address, Department of Chemical Engineering, University of Texas, .4ustin, Texas,
Collective Index of Analytical EditionProgress Report Work on the fifteen-year cumulative index t o ,the ANALYTICAL I A LENGINEERING CHEMISTRY,first anEDITIONof I N D U ~ T RAND nounced in t h e July issue, has gone forward steadily, and i t is now planned t o send the index t o t h e printer in November, so t h a t distribution can be begun early in 1945. T h e index will form a book about the same size a s an issue of t h e ANALYTICAL EDITION,and will be printed on t h e same paper. It is being prepared by Charles L. Bernier, Associate Editor of Chemicd Abstracts. I n t h e November 15 issue of the ANALYTICAL EDITION will appear a definite announcement of price and date of issue, with full instructions regarding placing of orders, for the benefit of those who have riot yet done this.
