August, 1928
INDUSTRIAL AND ENGINEERING CHEMISTRY
has changed by the several possible types of reactions, perhaps in different sequence, to a product of definite molecular complexity, does it change to solid. From this viewpoint the mechanism of solidification of drying oils, after the initial surface set, involves chemical change of the adsorbed, oriented liquid phase into molecules of the definite complexity characteristic of the solid. The solid then undergoes relatively little change except in so far as destructive agencies promote reactions of different nature and in general, opposite type. This view receives further confirmation from the fact, as shown in Table V, that the heat of combustion of the solid phase after extraction is sensibly constant. There is, of course, some variation in the films due to differences in spreading, drying, and thickness, but there is no real drift of the values in any direction. The heat of combustion of the extracted oil, on the other hand, decreases steadily from the much higher value characteristic of slightly oxidized oil. The heat of combustion of gel No. 4 was determined to be 8985 calories. This value, by comparison with the average value of 7205 given by the extracted films, indicates that in forming the gel structure by heat-bodying relatively little oxidation in the narrow sense of the term occurred. The ethylene linkages were used up mostly in couplings, whereas in the settling of films there is a stage, as shown by the heat of combustion curves, where the decrease in unsaturation runs coincident with a decrease in heat of combustion and an increase in the percentage of oxygen in the product. The changes a t this stage involve oxidation to a large extent.
809
The heat of combustion of the film calculated from the percentages of solid and liquid phases and their heats of combustion is in nearly every case higher than the determined value. This indicates that the adsorption of the liquid phase by the solid gel structure in the process of solidification of the oil is exothermic and confirms the promise of adsorption involving definite structure and orientation as against the idea of simple mechanical entanglement of liquid in the film. ULTIMATE ANALYSIS-corresponding to the change in heat of combustion, the ultimate analysis of linseed oil films (Table VI) shows a much greater percentage of oxygen than that present in the raw oil. Extracted films 14, 56, and 114 days old with driers, complete unextracted film 63 days old, and the oil extracted from it-all have very nearly the same composition. Their rather remarkable agreement suggests afresh the premise that the solid phase being formed in the solidification of the oil films is one of very definite composition and complexity, and that variations in the compositions of films as a whole are due to liquid phase which has not yet been sufficiently changed by the various reactions to produce this solid substance. As the films age the composition of the liquid phase approaches that of the solid. Acknowledgment
Acknowledgment is due and cheerfully given to the Pfister and Vogel Leather Company and to the Archer-DanielsMidland Company and the William 0. Goodrich Company for grants under which this work was carried out. The writers wish also to acknowledge the help given by J. G. Smull.
Studies in the Drying Oils'" IX-Action
of Cold-Blowing on Linseed Oil J. S. Long and W. S. Egge LEHIGHUNIVERSITY, BETHLEHEM, PA.
HE curves for the rate Linseed oil has been blown at 30" C. in the presence from certain points of view.* of various substances. In the presence of a positive The writers had previously of oxidation of linseed oil rise slowly for some catalyst, reactions occur which cause decrease in the blown linseed oil a t temperaunsaturation. Negative catalysts prevent this. t u r e s of 120" to 140' C., time, but after the initial induction period the slope inCombination processes-e. g., heating and blowingcorresponding to some blowc r e a s e s rapidly. The compermit accentuation of various types of reactions ingpractice, but they felt that plete curves are similar to and enable the operator to get a greater variety of even a t these temperatures products or to make a desired product more readily. the effects of oxidation were t h o s e o b t a i n e d in autoThioglycolic acid is suggested as a means for the too greatly masked by other catalytic reactions. Study of the oxidation of precipitation of lead, manganese, cobalt, iron, and other reactions which took place a t dryingoils by changesinfilms metals of groups I, 11, and 111 as usually classified in these t e m p e r a t u r e s , The on relatively non-porous surqualitative analysis, from drying oils, bodied oils, present investigation was unfaces is difficult. The penevarnishes, and like products-(a) for purposes of dertaken to eliminate this tration of oxygen in the staquantitative estimation, (b) as a means of study of masking and get some inforthe course of various types of reactions. This throws mation as to the nature and tionary oil is slow, and the depth to which oxygen penelight on the function of driers in oils, paints, and varcourse of the oxidation reactrates is not great unless the nishes. tions a t 30" C. oil is in motion. The film is Since the reactions are sustherefore often not uniform throughout. I n studying the pected of being autocatalytic to some extent, various subnature of the reactions which occur, it seems logical to use stances were tried to retard or accelerate the oxidation. conditions which permit (1) steady progress of the reactions, Materials and (2) uniform samples for examination. The blowing process Linseed Oil. Refrigerated linseed oil derived from Northfulfils these conditions to some extent and has been studied west seed was treated to remove the break, chilled to 6.6" C. Presented before the Division of Paint and Varnish Chemistry at to separate part of the saturated glycerides, and filtered the 75th Meeting of the American Chemical Society, St. Louis, Mo , April cold. Alkali-refined linseed oil was also used. These oils 16 to 19, 1928 had the following chara.cteristics: a This work was carried out under the New Jersey Zinc Company
T
Fellowship a t Lehigh University.
8
Chatterji and Finch, J . Sot. Cliem. Ind., 46, 333T (1926).
810
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
REFRIGERATED ALKALI-REFINED LINSEEDOIL LINSEEDOIL Specific gravity at 15.5°/15.50C. 0.9355 0.9364 Refractive index at 25O C. 1.4776 1.4782 Iodine number, Wijs (1 hour) 187.6 180.0 Hexabromide number 39.6 36.9 Acid value 1.91 0.8
Thioglycolic acid, c. P., made by the Eastman Kodak Company. Free fatty acids from linseed oil; titration shows about 100 per cent acids. Method
In each of the runs given in Table I, 300 grams of linseed oil were blown with a stream of dry air at the rate of 6.2 liters per minute. The oil was in a glass tower 37 em. high and 4 cm. in diameter. This tower was contained in a thermostat a t 30" C. The air was admitted a t the bottom of the column through a single orifice 1.5 mm. in diameter. The incoming air was conditioned by passing it through a solution of potassium hydroxide (1:1), then through concentrated sulfuric acid and glass wool. It then passed through a coil immersed in the thermostat, so that it was at the same temperature as the oil by the time it reached the tower. of Cold-Blowing on Linseed Oil SPECIFICREFRACTIVE IODINE HEXAAFTER GRAVITY INDEX ACID NUMBER BROMIDE BLOWING(15.5' c.) (25' c.) V A L U E (WIJS, 1 HOUR)NUMBER Table I-Effect
Hours SET 1-REFRIGERATED
OIL, WITH 0.1 PER CENT MANGANESE COMBINED AT 160' C.
0.9355 0.9422 0.9468 0.9580 0.9662 0.9820
1.4776 1.91 187.6 1.4782 2.3 179.8 1.4796 2.7 170.1 1.4824 162.3 4.4 1.4848 155.4 6.8 1.4880 141.2 9.3 (Color of samples, dark amber)
0 8 16 24 32 40
SET 9-ALKALI-REFINED
0 8
16 24 32 45
11.8
4.3
OIL, WITH 0.10 PER CENT MANGANESE COMBINED AT 30°C
0.9364 0.9420 0.9465 0.9872 0.9660 0.9818 (Color of samples,
SBT 8-REFRIGERATED
1.4782 0.8 180.0 36.9 1,4780 177.6 1.5 30.8 1.4792 175.4 22.0 1.6 1.4820 3.5 163.8 16.6 1.4842 4.2 152.6 9.5 1.4878 136.3 6.1 *3.8 extremely pale, almost water white)
0.9355 0.9410 0.9412 0.9416 0.9416 0.9418 0.9418 0,9355 0.9414 0.9414 0.9442 0.9468 0.9500 0.9522
SET E.-REFRIGERATED
6 12 18
1.4776 1.4780 1.4782 1.4782 1.4784 1.4788 1.4792
1.91 1.9 2.0 2.4 2.4 2.4 2.4
187.6 186.8 186.7 186.8 186.6 186.2 185.5
39.6 41.6 41.1 40.9 40.0 41.1 42.0
SET ?-FREE
8 16 24 32 40
1.4776 1.4782 1.4784 1.4788 1.4794 1.4802 1.4816
1.91 1.9 1.8 1.9 1.9 1.8 1.8
187.6 187.0 186.7 186.8 187.0 186.9 187.0
39.6 41.0 40.6 40.9 41.1 40.4 40.3
OIL, WITH 1 PER CENT SODIUM OLEATE AND 0.1 PER CENT MANGANESE
0.9426 0.9602 0.9822
S E T 6-REFRIGERATED
6 12 18
of Previous Heat Treatment o n Blowing. Set &Refrigerated Linseed Oil
Table 11-Effect
BLOWING NECES-
AFTERHEATING IN INERT TEM- HEXAATMOSPERA- BROMIDE PHERE
TURE
HOW'S
'c. 100 150 200 225 250 265 280
0.9424 0.9600 0.9818
1.4784 1.4830 1.4878
4.2 9.6 12.0
175.3 152.0 130.1
35.8 18.3 2.1
OIL, WITH 1 PER CENT CALCIUM OLEATE AND 0.1 PER CENT MANGANESE
1.4782 1.4828 1.4876
3.8 5.4 7.9
177.2 159.9 144.6
36.9 20.1 4.3
FATTY ACIDS OF LINSEED OIL, WITH 0.1 PER CENT COBALT COMBINED AT 30' C.
0.9038 0.9204 0.9438 0.9648 0.9804
1.4690 1.4724 1.4766 1.4810 1.4852
189.3 181.6 173.2 164.0 156.4
189.5 176.4 162.1 144.7 125.3
39.8 26.5 18.0 8.3 0.0
I n each of the runs given in Table 11, 100-gram samples of linseed oil were heated in an atmosphere of carbon dioxide at the specified temperatures for a period of 8 hours. The oil samples were then blown. The time required to reach a given body (refractive index 1.4880) is shown in this table. Table I11 gives preliminary data on the separation of driers from oils by. means of thioglycolic acid. Samples of c. P. driers were put into solution by warming with benzene,
NUMBER
39.2 28.3 15.7 8.6 3.8 1.9 0.0
~
SARY T O A G -
IODINE SPECIRIC *"IRE NUMBER GRAVITY ( W I J S , 1 HOUR) (15.5' c . ) 1'4880)
(n?
182.6 179.5 177.2 175.6 173.1 169.0 160.4
0.9408 0.9418 0.9432 0.9435 0,9462 0.9496 0.9502
Hours 42 38 37 2s 24 18 11
Table 111-Separation of Driers by Means of Thioglycolic Acid. Set +Refrigerated Linseed Oil WEIGHTO F R E S I D U E AETER W T . ON ADDINGTnroIGNITING 1 cc. GLYCOLIC ACIDBEFORE DRIER SOLN. IGNITING Gram Gram Cobalt resinate 0.0234 0.0230 Cobalt linoleate 0.0295 0.0294 Manganese resinate 0.0239 0.0236 Manganese linoleate 0.0292 0,0290 Lead resinate 0.0318 0.0318 Lead linoleate 0.0340 0.0338 Iron linoleate 0.0262 0.0259 Mixture of lead cobalt, and manganese resimtes 0.0256 0.0255
Bailey's modification of the Steele and Washburn method for the hexabromide number was used. I n determining acid values a mixture of alcohol and benzene (1:l) was employed as the solvent. Discussion of Results
C.
9 E T 4-REFRIGERATED OIL, WITH 0.1 PER CENT MANGANESE AND 0.6 PER CENT WNAPHTHOL COMBINED AT aoo c.
0 8 16 24 32 50 100
and filtered. I n each case 1 cc. of this solution was ignited and weighed. This was used as a blank test. One cubic centimeter of the same solution was added to 30 cc. of linseed oil and the mixture warmed until solution was complete. Five or six drops of thioglycolic acid (calculated to be an excess) were added and the samples set aside for 1 hour with occasional shaking. The precipitate was separated by means of quantitative filter paper, washed with V. M. P. naphtha, dried, ignited, and weighed.
OIL, WITH 0.6 PER CENT a-NAPHTHOL COMBINED AT 30'
0 8 16 24 32 50 100
39.6 33.4 24.1 17.9
Vol. 20, No. 8
The decrease in iodine number and hexabromide number in Set 1 (positive catalyst present) indicates that oxyglycerides are formed at the points of unsaturation in the glyceride molecules. The total decrease in hexabromide number corresponds to 0.353 X 0.367 = 0.1295 gram of that linolenic acid which forms the solid hexabromide. If two ethylene linkages in each molecule had become saturated 4 X 126.93
the decrease in iodine absorption would be X 278.24 0.1295 = 0.236 gram of iodine per gram of oil. The actual decrease observed amounts to 0.464 gram of iodine per gram of oil, which is approximately twice as great. This shows that the decrease in unsaturation cannot be ascribed merely to that linolenic glyceride which forms the insoluble hexabromide. In Set 2 the same general trend is noticed. The color of the samples is very pale. The acid value does not increase so rapidly as in Set 1. Morrell' has studied the effect of a-naphthol as a retarder or negative catalyst in the oxidation. I n Set 3, 0.5 per cent of a-naphthol was added to the oil before blowing. The hexabromide number increased at once from 39.6 to 41.6, and then remained sensibly constant throughout the run. This may be explained by assuming that the negative catalyst breaks down some linolenic oxyglycerides that had previously formed in the raw oil used. There was no bodying action in this run. Set 4 shows that a negative catalyst in combination with a positive catalyst inhibits the reaction almost as much as 4
J . Oil Colonr Chcm. Assocn., 10,275 (1927).
August, 1928
INDUSTRIAL AND ENGINEERlNG CHEMISTRY
a negative catalyst alone. This set shows a slight bodying action. Sets 5 and 6 show the effect of sodium and calcium oleate on the rate of bodying. The time to acquire a given body is about one-half of that required in Set 1. The oleates of sodium and calcium lower the surface tension and thus permit the immediate formation of a thick, stable foam. The interface between the oil and the air is increased greatly, permitting more rapid absorption of oxygen. Set 7 shows the variation of the constants, when free fatty acids of linseed oil are bodied by blowing. The acid value is reduced, showing that the carboxyl group is affected in the course of the reaction. In Set 8 samples of linseed oil were heated in an inert atmosphere (COZ) for 8 hours a t various temperatures. The hexabromide number falls off steadily and reaches zero in less than 8 hours a t 280' C. These samples were then blown to a given body (refractive index 1.4880). On the premise that one ethylene linkage in each molecule of linolenic acid has been saturated by heating, the decrease in hexabromide number is quite comparable to the decrease in unsaturation as measured by the decrease in iodine number. The oil has also bodied somewhat. It would seem, therefore, that the shorter time required to oxidize the previously heated oils is due to previous coupling reactions. The coupling reactions have produced molecules which cause the oil to have different characteristics-e. g., surface tension-from that of the original oil. The results and the products obtained in this run are not without significance in indicating that purposed combinations of treatments, each of which accentuates a certain type of reaction, will enable us to get a greater variety of products desired for various industrial processes and will also enable us often to get a certain desired product more surely and more easily than when we use one treatment-. g., blowing, heating, or raying, alone. Meyers5 has prepared various metallic salts of thioglycolic acid and has indicated some of their properties. The present writers found that thioglycolic acid (0.5 per 6
J . Lob. Clin. Med., 6, 359 (1921).
811
cent) added to the oil retards the bodying as does a-naphthol. They also made the interesting discovery that the addition of this acid precipitates the metals of metallic driers present in the oil. The precipitation is practically quantitative, as shown by the results in Table 111. The precipitated lead, manganese, cobalt, and iron derivatives of thioglycolic acid are insoluble in petroleum ether or in naphtha. The precipitate can therefore be washed free from oil and weighed. Thick oils made by heat-bodying or blowing can be diluted with naphtha before adding the thioglycolic acid. The metals are then completely precipitated from the diluted heavy-bodied oils in which they had been previously incorporated by heating. A few preliminary tests were made with resin varnishes. The metals were precipitated by the thioglycolic acid as in the case of raw or bodied oils. For scientific purposes the use of thioglycolic acid enables an investigator to study whether the function of a given drier lies in starting a reaction and building up bodies that then react on each other in later stages of the process (blowing, cooking, etc.), or whether the metal drier is needed constantly during the entire process to stimulate a certain reaction or type of reaction. The drier can be removed a t any time during the process and comparison thus obtained of its effect (1) when present all through the process, and (2) when present for only part of the process. It now becomes possible to use certain driers to promote desired reactions during the heating or blowing process and then to remove part or all of these driers from the processed oil and introduce the type and quantity of driers desired for the subsequent use of the product. This avoids the compromise necessary when the drier is used to promote reactions in processing, and then remains in the product and influences the oxidation of the product in paints, varnishes, and other protective coatings. The act that free fatty acids can be oxidized at 30" C. to a heavy body is of interest as indicative of reactions in the early part of the drying process leading to the formation of molecules of sufficient complexity to be a factor in the adsorption process, which seems to play an important role in the latter part of the process of solidification of drying oils.
Dialysis of Putrescible Liquids' 0.M. Urbain URBAIN
& HUNT,209 S O U T H
HE dialyses of putrescible liquids, such as domestic sewage and the waste solutions from tanneries, creameries, canneries, etc., present some unique problems. If the results of the dialyses are to be reasonably accurate, the bacterial decomposition and the oxidation of the putrescible material in such solutions during dialysis must be eliminated. A dialyzer constructed as shown in the accompanying drawing has been used for a number of years with excellent results. The dialyzing water consisted of distilled water, the dissolved oxygen of which had been expelled by boiling. A 25-gallon, bottle-shaped, tinned-copper vessel was used for this purpose. After boiling, oxygen traps were attached to prevent the entry of oxygen during the cooling period. The metal cover was then sealed in place over the dialyzing compartment. The air was removed from the compartment by aspirating nitrogen through the area by means of the petcocks in the metal cover. Dialyzing trays made of S & 1
Received May 14, 1928.
HIGH ST.,
COLWMBUS, OHIO
S parchment paper were used and found to be very satisfactory. Several samples may be dialyzed at one time. The dialyzing area was maintained at a temperature near 0" C. by means of the ice jacket.
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