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INDUSTRIAL A N D ENGliYEERING CHEMISTRY
It has long been known that certain inorganic salts have accelerating and others retarding effects on the activity of enzymes. The effect of solutions of various inorganic salts on the activity of lipase in hydrolyzing linseed oil is therefore included. Lipase material for the experiments to determine the effect of inorganic salts was obtained from mature flaxseed. The seeds were ground with sand in a mortar. The resulting mixture was added to 400 cc. of linseed oil. The samples were then allowed to stand in a thermostat adjusted to 36.8” C. At the end of certain intervals the acid value of the samples was determined. Results of these determinations are given in Table IX. Apparently inorganic salts retard the activity of flaxseed lipase in hydrolyzing linseed oil.
Vol. 21, No, 12
zymatic material that later had found its way into the oil in dust or by some other means. To test this, a suspension of 0.2 gram of flaxseed meal taken from the presses during regular production was added to 400 grams of linseed oil and allowed to stand for 8 weeks with a 5-minute agitation daily. Blanks were run in which the meal was omitted but the oil and water mixture otherwise the same. I n each of six samples with meal and in 2 with ground press cake there was decided and steady acid value increase, indicating the presence of lipase not inactivated at the temperature of the presses (90’ C. maximum). The enzymatic activity of the meal from the hot presses’ was found to be approximately 40 per cent of that of meal obtained from mature seeds after ether extraction of the Oil.
As the oil forms in the seeds, the enzymatic activity of the lipase present decreases (Figure 5).
Discussion of Results
The usual method of obtaining linseed oil from flaxseed in the United States is by hot pressing, whereby the oil is pressed from the seeds by hydraulic pressure at a temperature of approximately 90” C. This temperature would be expected to inactivate any enzyme present in the seeds. Therefore linseed oil normally would not be expected to change from enzymatic activity upon standing. It has been observed, however, that in some cases the acid value of the oil has increased upon standing. It was thought that this might be due to hydrolytic activity of enzymes in the oil which had not been inactivated by the treatment or to en-
Acknowledgment
The help given by A. C. Amy, of the University of Minnesota, and A. H. Wright, of the University of Wisconsin, in raising the flax and obtaining the samples for this investigation is acknowledged. This work is part of the research program on drying oils of Archer-Daniels-Midland Company and William 0. Goodrich Company, and affiliated companies. Acknowledgment is due these companies for permission to publish the results. 1
Lorberblatt and Falk. J . A m . Chem. SOC.,48, 1655 (1926).
Relation of Adhesion Tension to “Liquid Absorption”” F. E. Bartell and 0. H. Greager UNIVgRSITY OF MICHIGAN, ANN ARBOR, MICH.
Liquid absorption values (Gardner-Colemanmethod) HE determination of A definite attempt to correhave been determined for three powdered solids with a the so-called “oil ablate “liquid absorption” and series of different liquids. Adhesion tension values sorption” values of piga d h e s i o n tension was first were either available or were obtained for each system. merits has become a common m a d e b y Baldwin (I). He Both sets of data were obtained with identical practice in the paint and made use of the limited data materials. color varnish industry. A then existing in the literature A simple linear relationship has been found to exist knowledge of these values (2, 3, 4 ) f o r t h e a d h e s i o n between liquid absorption and adhesion tension for all t e n s i o n s of various liquids serves as an aid in regulating those systems in which the liquid forms a zero angle a g a i n s t c a r b o n and silica. the character of the finished of contact against the solid. The liquid absorption is From these data, t o g e t h e r product. the least for those liquids which show the highest with his own values for the At present it appears to be adhesion tension against the solid. liquid absorptions obtained generally conceded that “oil For those systems in which the liquid forms a finite with similar liquids and supabsorption” values are, for contact angle against the solid the liquid absorption p o s e d l y similar solids, an the most part, dependent on is lower than would be expected from the foregoing equation was formulated to three factors: (1) the specific express the interrelation of relationship. The larger the angle of contact (and the surface of the solid material, liquid absorption, specific surless the adhesion tension) the less the oil absorption. which is governed chiefly by face. and adhesion t e n s i o n . the fineness of the pigment powder; (2) the degree of wetting of the solid by the liquid The adhesion tension data available to him, however, were phase; and (3) the method used in making oil absorption rather limited for a critical treatment. Moreover, it has remeasurements. It has been shown (2) that the degree of cently been shown that carbon blacks from different sources wetting of a solid by a liquid can be determined by means of show quite different adhesion tension values against given adhesion tension data and can be expressed in t,erms of liquids (5). I n the light of additional data it is felt that, alabsolute units. It follows, then, that a definite relationship though Baldwin’s views are in general correct, the conclushould exist between “liquid absorption,” to use the more sions drawn from his work are somewhat in error and the equation presented by him is not justified. general term, and adhesion tension.
T
1 Presented before the Division of Paint and Varnish Chemistry at the 78th Meeting of the American Chemical Society, Minneapolis, Minn., September 9 to 13, 1929. f The material presented in this paper is from a dissertation submitted by Greager to the Graduate School of the University of Michigan in partial fulfilment of the requirements for the degree of Doctor of Philosophy, 1929.
Experimental
The data presented in this paper were obtained with the three solids silica, carbon black, and calcium fluoride. The determinations of the liquid absorption values for the first
December, 1929
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INDUSTRIAL AND ENGINEERING CHEMISTRY
two solids were made with materials identical with those used by Bartell and Osterhof in their work on adhesion tension. I n addition, use was made of their more complete data, which unfortunately are as yet unpublished. Calcium fluoride was-used, not because it has any interest as a pigment, but because fairly complete adhesion tension data for this solid had recently been obtained by the writers. The determination of liquid absorption was carried out according to the method of Gardner and Coleman (6), as follows: Twenty grams of powder are placed in a beaker and the liquid added slowly from a buret. As the liquid comes in contact with the powder, the particles thus made wet cling together and form a small ball of paste. Further additions of liquid are directed onto this ball, and the surrounding dry powder is lifted from the outer edges and placed over it. Finally, all the powder will be incorporated in the large lump of paste. Up to this point, the mass will not smear the walls of the glass container; in other words, the wetting property toward an external phase is absent. The addition of one or two drops a t this point, however, will cause the mass to soften and smear the glass. This is the end point of the determination. The liquid absorption factor is then expressed as the volume of liquid (in cc.) required to saturate 100 grams of material. The data for the three solids (Table I) lead to conclusions somewhat different from those presented by Baldwin. When the liquid ab0 7 sorDtion values a r e E o. plot'ted against the adhesion tension values, t h e c u r v e s shown in k a Figures 1, 2, and 3 are o btained. A linear " relationship b e t w e e n 2 liquid absorption a n d -s a d h e s i o n tension a p ? x 509 pears to exist for liquids II which w e t t h e solid zP --I w i t h a zero angle of 40 3 2 ' 4b 418 516 72 80 c o n t a c t . It will be
s -
&-
L '
' ' ' i+ ' '
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angles have been determined, the extent of the deviation increases as the angle of contact increases. This irregular behavior on the part of liquids which form finite angles of contact against the solid and also the scarcity of published data on adhesion tension referred to were undoubtedly the cause of Baldwin's erroneous interpretation of his results. I n his work the logarithms of the adhesion tension values were plotted against the logarithms of the liquid absorption values. This brought the points for the liquids which form finite angles of contact into line, but the points representing the values for some of the other liquids fell away from this line. He assumed the deviation in these cases to be due to experimental errors.
--
Adhesion Tension ( d y m per cm.) Figure 2-Silica
The results obtained in the present work indicate that a simple linear relationship exists between adhesion tension and liquid absorption for those liquids which form a zero angle of contact against the solid. The deviation from this relationship in the case'of the other liquids is neither accidental nor the result of the presence of impurities and may, we believe, be logically explained as follows. Let us first consider the case of two liquids between parallel plates and in contact with the plane surface of the lower plate. Consider that one liquid ( A ) will wet the surface with a zero angle of contact, while the other ( B ) forms with it a definite equilibrium contact angle. A drop of liquid A , when placed on this surface, will spread indefinitely, or until a t least a monomolecular layer has been formed. A drop of
440 01
420
Degrees Calcium 1 Methylene iodide fluoride 2 Tribromohydrin (Figure I) 3 a-Bromonaphthalene 4 Bromobenzene 5 Chloroform 6 Toluene 7 Benzene 8 Bromoform 9 Ethyl carbonate 10 Butyl acetate 11 Water Silica 1 a-Bromonaphthalene (Figure 2) 2 Benzene 3 Toluene 4 Chloroform 5 Butyl acetate 6 Ethyl carbonate 7 Isobutyl alcohol 8 Water Carbon 1 Water black 2 Isobutyl nlcohol (Figure-3) 3 Ethyl carbonate 4 Butyl acetate 5 Decalin 6 Tetralin 7 Benzene 8 Toluene 9 a-Bromonaphthalene Numbers agree with numbers used in
32.50 16.25 12.50
42.3 43.0 43.0 0 46.1 48.5 0 48.5 0 50.1 0 50.7 0 0 65.9 0 65.2 76.5 0 41.9 19.90 52.4 0 0 54.7 0 60.0 0 73.5 0 74.3 0 81.1 82.8 0 40.60 54.7 0 56.6 0 65.6 0 65.8 0 76.4 0 76.7 0 81.1 0 82.1 0 89.2 Figures 1, 2, and 3.
51.0 54.5 60.0 62.0 59.0 60.5 59.5 58.0 48.8 47.5 42.5 58.0 65.5 66.0 63.5 61.0 59.5 58.0 58.5 382 436 416 424 400 396 392 330 370
4
zz g 360
34050
60
70
80
90
100
Adhesion Tension (dynes p%r un> Figure 3-Carbon
Black
liquid B, however, will spread on this same surface only until a configuration of the drop which corresponds to the equilibrium contact angle for this system has been reached. I n other words, if several drops of liquid A were placed on this surface they would all coalesce in time, but several drops of liquid B might be arranged in such a manner that, on spreading out until the equilibrium contact angle was reached, no two drops would meet and coalesce.
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Next there may be considered the amounts of these two liquids that it would be necessary to add before a point of contact would be established with the upper parallel plate. I n the case of liquid A , which spreads with a zero angle of contact, the addition of successive amounts would result in the formation of uniform layers of increasing height, until finally contact would be established with all points on the plate a t once. The volume of liquid that had been added up to this point would be equal to the product of the area of the bounded surface and the distance between the plates. I n carrying out the same test with liquid B , however, contact could be established with the upper plate before a volume corresponding to that for liquid A had been added. That is, individual drops could reach the necessary height without
A
B Figure 4-Angle
a
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b of Liquid Absorbed Is Dependent upon Contact Angle
Figure 6-Amount
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of Contact for Liquids A a n d B Figure 7-Attractive
having spread out to such an extent that they would coalesce with other drops. A considerable portion of the volume between the plates would, in such a case, be occupied by air. The larger the angle of contact, the greater will be the amount of air entrapped, and consequently the greater will be the deviation from the normal relationship. This will be seen from Figure 4, which represents two liquids of different contact angle, 0, between the parallel plates. As the drops become larger, conttact is finally established with the upper surface. The equilibrium angle, 0, for a given liquid must always be the same (disregarding gravitational effects), regardless of the size of the drop. Thus, the larger the angle, the less liquid will be required to establish contact with the upper surface. This is the case for the liquid shown in Figure 4,A which has an angle of contact greater than the liquid shown in Figure 4,B.
solid by the liquid, the interface can advance only to the position where the configuration of the solid particles forces it to meet the solid with the equilibrium contact angle. For a liquid of small angle of contact, the interface would take up the position a t b; if the angle is larger, the interface would be a t c. Thus, as for the above case of two parallel surfaces, the greater the angle of contact the greater the amount of air entrapped, and accordingly a lesser amount of liquid would be held within the powder. This is shown in Figure 6, in which a represents a clump of solid particles wet with a liquid of small or zero contact angle. The various interfaces are well out toward the pockets, and wide bands of liquid are held in the powder. With a liquid of larger angle of contact ( b ) ,the interfaces are furtsherremoved from the pocket, and the bands of liquid held in the powder are narrower. finite tontact Angles K
I I
Pecreasing Amount of Liquid Phase Figure 5-Volume of Air Entrapped Is D e p e n d e n t u p o n Contact Angle
When dealing with the particles of a powder, the case is but little different. It is probable that air is never completely displaced from the powder (in the Gardner-Coleman method) with liquids which form finite contact angles. Assuming spherical particles, the void or pocket between these particles would appear as shown in Figure 5. When liquid is introduced between these particles, the liquid-air interface takes up a position according to the angle of contact. If the angle be zero, the interface will advance as far as possible toward the pocket, and the air bubble if entrapped will tend to be spherical. This position is indicated as a in Figure 5. If a finite contact angle is formed against the
Force Operative through Liquid Layer between Solid Phases
~
Zero Contact Angle Entrapped Air
1
Zero Contact Angle No Entrapped Air
Maximum Amount of Liquid Phase
Decreasing Amount of Liquid m a n
IncreasingAdhesioh Tension Figure 8-Amount of Liquid Absorbed Is Dependent upon Adhesion Tension a n d Contact Angle
From Figures I, 2, and 3 it is apparent that the amount of liquid with zero contact angle absorbed by a powder decreases in proportion to the adhesion tension solid-liquid, Without attempting a critical treatment of this relationship, it may be tentatively explained as follows: In a 2-phase solid-liquid system, the solid exerts a certain attractive force on the liquid. Regardless of the precise nature of the attraction gradient from the solid-liquid interface into the liquid, a preponderance of evidence indicates that the influence is operative over many molecular layers.
December, 1929
INDUSTRIAL AND ENGINEERIXG CHEXISTRY
This is shown diagrammatically in Figure 7. The liquid between two particles in a paste, as represented by liquid molecules (a), might thus be attracted by both solid surfaces. With a limited amount of liquid, the tendency will be to draw the particles closer together, and the stronger the attraction (or the higher the adhesion tension) the greater will be this tendency. It follows that the closer together the particles the smaller would be the amount of liquid which could be held in the paste. I n other words, the greater the adhesion tension of the liquid against the solid, the less will be the volume of liquid that will be required to “wet” the powder. This relationship was actually found in the experimental work. I n view of the foregoing discussions, it becomes evident that the amount of oil held by the powder may depend to quite an extent upon the precise method employed in bringing together the oil and the powder. Greatest variations are to be expected with liquids giving a large angle of contact with the solid. With such liquids much entrapped air may be held. It is believed that a fairly exact representation of the condition which may exist within a system of a powder wet by different liquids is given in Figure 8. Here the particles of powder are represented as spheres. The relation of volume of liquid to volume of entrapped air is shown by the black and white portions, respectively. At the left is represented a
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liquid having a large angle of contact, resulting in relatively small volume of liquid and large volume of air. The central portion of the diagram represents conditions when a zero contact angle is approached. With liquids which wet more completely, air would be displaced from the solid and would tend to escape from the mass. A liquid giving a high degree of wetting (high adhesion tension) would tend to displace the air completely. As the adhesion tension is further increased, the solid particles are drawn closer together, with the result that the relative amount of liquid held by the solid becomes less. If the above-expressed views are correct, it follows that the maximum of “liquid absorption” should be obtained with those liquids which give an intermediate degree of wetting against the solid. The most favorable condition for high oil absorption by the Gardner-Coleman method would be obtained with a liquid giving a zero contact angle with the solid, but having a low adhesion tension against the solid. Literature Cited Baldwin, IND.ENG.CHEM.,21, 326 (1929). Bartell and Osterhof, I b i d . , 19, 1277 (1927). Bartell and Osterhof, 2. physik. Chem., 190, 715 (1927). Bartell and Osterhof, Colloid Symposium Monograph, Vol. 5, p. 1 1 5 (1927). (5) Bartell and Smith, IND. END. CHEM.,21, 1102 (1929). (6) Gardner and Coleman, Paint Mfrs. Assocn. U. S., Tech. Circ. 86.
(1) (2) (3) (4)
New Solvents for the Active Principles of Pyrethrum’ W. A. Gersdorff and W. M. Davidson BUREAU OF CHEMISTRY AND SOILS, AND FOOD,DRUG,A N D INSECTICIDE ADMINISTRATION. U . S. DEPARTMENT OF AGRICIILTURE, WASHINGTON, D.
HE kerosene extract of
T
pyrethrum (Chysanlhemum c i n e r a r i a e folium, Trev.) now appearing on the market in large quantities possesses several characteristics which restrict its uses. Among these are combustibility, immiscibility with water, and injurious action on the foliage Qf plants. The investigathn here reported was conducted to find solvents that able characteristics.
A number of solvents, some miscible with water and some immiscible, some flammable and some nonflammable, completely remove the active principle of pyrethrum for practical use against Myzus persicae Sulz. Many of these vehicles are suitable for application on plants as resistant as cabbage because they do not injure the foliage, whereas kerosene causes such severe injury that it is unsuitable. At 5 per cent concentrations all the extracts tested except xylene and amylene dichloride give effective control against Myzuspersicae Sulz, without injury to cabbage. -
are free from these undesir-
Table I-Quantity
of Material Extracted f r o m Pyrethrum by Various Solvents BOILING POINT TOTAL MATERIAL EXTRACTED AT: SOLVENT Boiling temp. Room temp. Per cent Per cenf O c. Methyl alcohol 24.6 19.2 65 Ethyl alcohol (95 per cent) 22.1 18.4 7s 82 Isopropyl alcohol 14.7 10.2 9.0 118 Normal butyl alcohol 17.4 8.8 Secondary butyl alcohol 100 13.7 83 9.5 12.6 Tertiary butyl alcohol 6.9 80 Benzene 6.2 138- 139 6.9 Xylene 6.9 Carbon tetrachloride 77 6.3 5.3 8.1 Chloroform 7.1 61 7.2 84 Ethylene dichloride 6.6 145 17.9 Amylene dichloride 12.5 5.2 121 8.5 Tetrachloroethylene 126 9.7 Diethyl carbonate
1 Presented by W. A. Gersdorff and W. S. Ahbott before the Division of Agriculture and Food Chemistry at the 75th Meeting of the American Chemical Society, St. Louis, Mo., April 16 to 19, 1928. Revised manuscript received August 19, 1929.
c.
Procedure
About 50 pounds of finely ground pyrethrum were well! mixed. To test the thoroughness of the mixing, eight 2gram samples were taken at. different places for nitrogen determination. The percentages of nitrogen found--1.77, 1.71. 1.77. 1.77. 1.74. 1.77. 1.79; and ’1.77Lshowed that the supply was well mixed. Extractions were made a t room3 temperature and a t the boiling temperatures of the solvents. In each extraction a quarter of a pound (113 grams) of t h e pyrethrum was used and the resulting solution was made to. 1 liter. The apparatus for extraction a t room temperature consisted of percolators made of 2-inch glass tubing. Ten-inch (25.4-em.) lengths were drawn down a t one end to a diameter of ”8 inch (0.9 cm.). The constricted ends were loosely plugged with cotton, and the pyrethrum powder was lightly packed over it. The method of extracting a t room temperature was the ordinary method of percolating. Successive portions of the solvent were added until all soluble matter had been dissolved and washed out. A preliminary determination of the amount of residue in successive extractions showed that the color of the solution indicated very well the attainment of this object. For the extraction a t the boiling temperature of the solvent the apparatus used was of the Soxhlet extractor type, but so. modified as to allow the use of a quarter of a pound (113
