BITUMEN-AG Modification
EGATE A HESION J
hemica
reatment
JOHN M. SWANSON’ I?niversit,yof Wisconsin, Madison, Wis.
Methods of increasing water-displacement properties and adhesion of bituminous materials toward commercial road aggregates are discussed from the standpoints of efficiency and practicability. Specific modifications of the general method suggested by McLeod-that of treating the aggregate with solutions of a heavy metal salt and a soluble soap in such a way as to produce a coating of insoluble soap which is better wetted by bitumen than by water-have been developed as promising for practical road constiuction. This type of treatment has been applied to plant mixes, and the process tested on a small scale in the field. Details of the procedure are presented. The successes and failures of the road panels are briefly considered.
acetic, propionic, or butvric, arid one high-molecular-weight ra.dical such as that from naphthenic acid ( 1 1 ) ; oleylamine (l9): and a n oil-soluble mater-soluble heavy metal salt (5). According to the second method of approach, the characteristics of t’heaggregate surfaces may be modified by chemical conditioning in such a way that they have a greater adhesion tension for asphalt,^ than for water. To change the wetting characteriptics of the aggregate, Winterko~n(15, IS) precoated the aggrcLgate with a resin, and McLeod ( 7 ) precipitated insoluble soaps 011 the aggregate surface. Winterkorn (14) had previously employed somewhat the same idea as McLeod in treating soils with wat,ersoluble soaps. Other procedures have been suggested which do not fall ex.actly into these two classifications. They include treatment of the aggregate n’ith a small quantity of hydrated lime, with subsequent bonding of the mist,ure with a n asphalt containing A small quantity of a water-insolllble metallic salt of an organic acid and a small quantity of a free organic acid (IO); coating of the aggregate with aluminum olaa.te, oleic acid, and light lubricatin:: oil, followed by the bitumen ( 8 ) ; and treatment of the aggregate, first wit,h a salt of an alkaline earth metal (particularly in the case of siliceous materials), and then with a coating of aspha.lt, containing oleic acid (4). St,ill another procedure for utilizing damp aggregate in road construction which should be mentioned, although it should not he considered capable of altering the adhesion tension between bitumen and aggregate, involves the use of bituminous emulsions. This t,ype of procedure has heen limited in commercial applirat,ions. Winterkorn and inore recently Mack ( 6 ) have described the application of such measures in the construction of test road panels. Mack prepared his test road sections by first treat,ing the aggregate with a solution of lead nitrate and then coating it with a n asphalt containing lead naphthenate. He obtained A marked increase in srabilit,y and water resistance and his t,est sections were still in good condition after four years a,nd four months of service. A procedure was worked out in this laboratory and applied on a pilot-plant scale by which it, is possible to condition the surface of various types of aggregates so that the surfaces of these particles will be preferentially wett,ed by bitumen. The method, a modification of the plan suggested by McLeod, involves treatment of the aggregate with solutions of a heavy metal salt and a soluble soap to produce surfaces which are preferentially wet by tjhe bitumen. Among other things, it was found that the “bladi liquor soap” obtained in the sulfate production of wood pulp (or the product formed by neutralizing with a base) had excellent properties as soluble soap. I n this way the treatment, become cheap enough t o ma,ke it practical in use.
IMPORTANT factor in the service life of a bituminous road matte is the ability of the bituminous material to resist the stripping action of water. Each year considerable stretches of thin-matte bituminous highm*ay must be repaired and sometimes relaid because heavy rains, coming shortly after construction, have washed some of the aggregate free of bitumen. If the adhesion tension of bitumen to aggregate could be raised sufficientJy above that’ of water to aggregate so that this stripping could be a,voided, a considerable saving would result. If t,he butumen-aggregate adhesion could be made much greater than the water-aggregace adhesion, additional benefit would result. The rather cost,ly process of predrying the aggregate, as pract,iced in “plant mix” construction, and the time-consuming air-drying process of current “road mix” construction could be avoided. Wet aggregate would be as amenable to coating with bitumen as dry aggregate, since the bitumen could force the water from the aggregate surface, and selectively displace it. The object of the work described here was to survey the possible approaches to the problem of increasing the bitumen-aggregate adhesion, to select a promising method, and, after deteimining t,he optimum conditions for its practice, to evaluate its effectiveness on a small sca!e under field conditions. To be considered for service tests it was stipulated that any treatment should meet the following requirements: I t should permit the use of water-wet aggregate, i t should prevent the stripping of the bitumen from the aggregate by water after placement of t.he matte, and it should be economically feasible. There are two general methods of approach tmothe problem of increasing bitumen-aggregate adhesion in a road matte. I n the first, the wetting characteristics of the asphalt may be altered by the addition of soluble, surface-active agents. Materials suggest,ed as addition agents for asphalss to improve their wetting characteristics and water resistance include: the sulfuric acid or arylsulfonic acid esters of the lower primary aliphatic alcohols (8); sulfo compounds (9); wax, to the extent of 2 to 10% ( I ) ; wood liquid-rosin acids, such as tallol, and ferric or aluminum sulfate ( I S ) ; a polyvalent metal compound cont,aining a t least one lowmolecular-weight radical derived from a n organic acid, such as 1
GENERAL METHOD
A largc portion of the work consisted of making mixei, oi aggregate, bitumen, and reagents, and testing them for adhesion b> a n adaptation of the Riedel and Keber test and the stripping test, both described by Klntcrkorn ( 1 6 ) . For the preliminary studies such fine grained agprrgates were used as stanilard
Present address. 13. I . du Pont de Nemours & Company. Ino., Wil-
minpton, Dol.
584
June, 1944
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Ottawa sand and other stone crushed and graded to the same . gram mixes were made up and size ( P w - R ~ ~ )Seventy-five allowed t o stand overnight, or a t least 12 hours, before testing for adhesion. For confirmatory tests 600-gram samples of commercial aggregate of standard gradation were mixed with a trowel in large pans. I n the Riedel-Weber type of test, a 2-gram sample of mix and 6 or 8 cc. of solution were placed in a test tube; the tube was immersed in a boiling brine bath and removed one minute after the solution had reached active boil. The standard series of ten solutions were used, starting with water and following with 1/256 M sodium carbonate solution and then with solutions of double the preceding concentration up t o 1 M . The degree of stripping caused by each solution was noted, and the concentration of the solution which produced complete stripping was taken as the end point. I n additilon, the appearance of the individual samples after each test was briefly recorded. The saturated salt bath was useful in t h a t it boiled at 107" C.; it was thus possible t o raise any of the ten solutions to the boiling point in about the same time, as well as to make the point of starting time sharp. Both factors were important if reproducible results were t o be obtained. This type of test was used because of its convenience. All significant mixes were further tested by the water stripping method, using apparatus and procedure as described by Winterkorn but with different times and temperatures. The procedure Invoived: 15-minute agitation of 50-gram sample i n water a t 75' F. (24' C.), 15-minute agitation of same sample at 100" F. (38' C.), 15-minute agitation at 125" F. (52' C.), and 15-minute agitation at 140' F. (60" C.). Inspections were made at the end of each 15-minute period, and a report recorded on the percentage of stripping of t h e coarse, the intermediate, and the very fine aggregate, as well as on the appearance of the solution and state (separated or emulsified) of the oil removed from the aggregate surface. Investigation showed t h a t end points could be duplicated consistently by the same as well as by different operators, and the descriptions of individual samples which had been tested agreed very well.
VE A O E ~ TABLEI. EFFECTOF SURFACE-ACTI
FACTOR Coverage on wet ailica without agent Coverage on wet limeatone without agent General action toward addition agents Action of aliphatic alcohols as addition agents on silica or limestone Action of ayclic alcohol (tetrahvdrofurfural) on silica or limestone Action of phenolic oompounds as addition agents on silica
'
OILA Poor b u t better than oil B Same
On, B Very poor Same
Generally good : several Bame treatments effective Ineffective Ineffective Good
Very poor
Phenol poor, resorcinol poor, cresol poor, pnitrophenol good
Phenol poor, resorcinol poor, cresol poor. pnitrophenol poor Ineffective
Action of phenolic com- Ineffective pounds as addition azents on limestone Action of aliphatic mono- Bame basic acids (up t o caprylic) on silica Action of aliphatic mono- Fair (above butyric) basic acids (up t o caprylio) on limestone Action of lauric and steario Lauric good and stearic good (with melted acids (both solid at room temp.) on silica or limeacids) stone .4ction of basic agents on Quite effective silica Action of basic agents on Ineffective limestone Amount of cationic re1 agents needed (relative). o n silica
Same Fair (above butyria) Laurio good and stearic good (with melted acids)
Poor, excapt for some containing primary amine group Ineffective 4
comparative data for the effectiveness of these particular reagents are not available. Water-insoluble soaps have found general application as waterproofing agenks; being soluble to a limited extent in bituminous materials, they have been incorporated in a number of the treatments suggested to increase the water-repellent properties of bituminous road matte. The effectiveness of aluminum stearate wm tested by dusting it on dry aggregate prior t o mixing in bitumen, by dissolving i t in the bitumen, and by coating the aggregate with a film of the water-insoluble soap by deposition from a benzene solution. A few representative results are shown in Table 11. The adhesion of the bitumen to the aggregate was vastly improved by the presence of aluminum stearate. However, it was evident that for any practical procedure a method of application is required which permits the use of much smaller amounts of the water-insoluble soap and achieves the coating of aggregate by bitumen in the presence of water.
PRELIMINARY INVESTIGATION
Some fifty different surface-active agents were tested for their effect in improving the water-displacement ability of bitumen in a bitumen-water-aggregate system. Agents were selected by type: those capable of forming solutions in the bitumen; those possessing acid or basic groups which might be expected t o react with the aggregate surface; and those whose polarity is higher than that of water so that (according t o the theory of I l k , 3) they might be expected to be selectively adsorbed by the aggregate surface from water and, when adsorbed, to present a surface preferentially wet hy bitumen. The mixes were made as indicated under "General Method". Ottawa sand and limestone ground to the same size were used as aggregates and two oils, of naphthenic and paraffinic bases designated A and B, respectively, were chosen to represent extremes in affinity towards the two aggregate materials. One hundred grams of the aggregate were first thoroughly soaked in water and drained, the surface-active agent was added to the aggregate and carefully mixed in, and the oil was finally added. A 0.5-cc. portion of agent was first tried. If this was sufficient, less was used; if not, the quantity was increased stepwise to a maximum of 6 cc. The surface-active agent was added directly t o the aggregate rather than being dissolved in Lhe oil; the addition agent showed highest efficiency under these conditions, since it did not have to migrate through the viscous oil to the oil-aggregate interface, the point, of usefulness. A summary of the results is given in Table I. The general conclusion was that surface-active agents are too specific both with respect to the bituminous material employed and to the nature of the aggregate surface t o be practical. Since a variety of chemically different surfaces are encountered in the average commercial aggregate, such selective action is disadvantageous. It would be particularly desirable t o develop a type of treatment which could be made independent of the nature of the aggregate and of the oil employed in road construction. A number of addition agents for asphalts have been recommended, especially in the patent literature. Unfortunately.
585
EXPERIMENTS RASED ON MoLEOD REPORT
From a practical point of view it was still considered better t o modify the chemical characteristics of the aggregate surfaces
.
TABLE 11. EFFECTOF ALUMINUM STEARATE ADDEDIN VARIOUS WAYS A I Stearate . -
Oil, as % of Aggregate 4.28
' %onsoap oil 20
Form of treatment D r t o aggregate
Mixed, commercial
4.4
20
D r t o aggregate
1/18
Limestone
5 7
20
Dry t o aggregate
1
Quartaite Mixed, commercial Quartzite
4 28
4.4 4 28
20 20 30
To oil To oil Dry t o aggregate
1/4 1/64-1/32
Quartzite
4.28
40
Dry t o aggregate
L/84-i/J1
hlixed. commercial
4 4
30
Dry t o aggregate
1
..
..
Aggregate Quartzite
basis
6.642
a.)
6 . 6 5 8 g.)
(0.855 9.1
Molar Concn. of NanCOs" l/64
'/ma
(0.963 p.) (1.284 9.)
..(0.987 . g.) ..
Without treatment . ., . HnO t o (all aggregates) '/266 Required ' t o biin about complete stripping under test conditione (Riedel and Weber t e s a .
INDUSTRIAL AND ENGINEERING CHEMISTRY
586
Vol. 36, No, 6
8.0
stepwise with continuous ing” action, rather than s the mix, wa? esqential if complete coverage wa. to be obtained without balling (this wab showri t o be particularly critical in subsequent field 6.0 tests). ( e ) The cost of the chemical reagerai. and treatment could be brought down t o a levt. sufficiently low to make the process economical by use of the black liquor soap or the soap pic#duced by reacting crude “tallol” fatty acids uitit a base; either of them proved fully as effertilt 4.0 a5 the iefined soaps. When properly applied, the treatment p i c duced 90 t o 100% complete coverage in tha presence of large amounts of mater (sufficien: to immerse a portion of the mix) and increasea 2.0 the resiqtance t o stripping from a rating of “verj to a point beyond the most stringent conditions of the tests used. The data o4 Table 111 are pertinent. Mixes were prepaieti 0 n i t h a pure quartzitic aggregate, a limestorrr 2.0 4.0 6.0 8.0 and several commercial aggregates of mixed con]position as well as with oils from various fieldCC.O.0JN M O N O V A L P A i T W E T T i N G A G E N T cracked products, tars, and cutbacks; all gavc equally satisfactory results. These observatioi, , Figure 1. Range of R a t i o s of T r i v a l e n t Salt to hlonov a l e n t S o a p for C o a t i n g Aggregate demonstrated that for practical purpose5 t h effectiveness of the treatment was independen; Full lines and legend. MrLeod: dotted lines and points, this work. of the nature of the aggregate and of the brtuminouo material employed. I t khould ~ I C t,han Lo add mat,erials to the biturnen. An extensive aeries of riuted, however, tha,t with coal tar the minimum reagent 1’1 rxperiments was therefore based on the PIlIcLeod report ( 7 ) . quirements werr about t x o - t h i d s &ti grr.,b a-. those for t h r petri,4 solution of a heavy metal salt was mixed with wet aggregate, lrum aqphaltq. followed by t h e addition of a solution of water-soluble soap. fn the reaction a water-insoluble soap was formed in the system contained d h i n the interst>ices of the aggregate. During thr, mixing process the aggregate surface was coated with the inrquivalents of a trivalent metaliir calt t o t w o of a monovaleiit soluble soap t o change its behavior from hydrophilic t o hydrowater-soluble soap. The rejultq of this work suggest t h a t tht phobic. ratio one equivalent of metallic ion t o one equivalent of sonyr Exploratory experiments using Ottawa sand and limestone is the most effective combinaton. A summary of the McLeoo ground t o the same size ( P ~ o - R ~aso aggregate ) materials with oils rxperiments is presented graphically by the solid lines of Figur A and B confirmed McLeod’s findings: Coating could be This figure shows the range of ratios of trivalent metallic achieved in the presence of water, and the presence of the water(termed “activating agent”) t o monovalent soap (termed “57 e insoluble soap greatly enhanced the adhesion of the bitumen t o tung agent”) within which bitumen would coat wet, siliceoi the aggregate surface. Experiments were then directed toil-ard aggregate by the McLeod procedure. applying the method t o conimcrcial aggregates. The areas of failure t o coat were obtained by adding to a m i x In t,he second group of experiments aluminum sulfate wztture of wet Ottawa sand and bitumen a given amount of chosen as heavy-metal salt, and either sodium oleate or the “black vating agent, and then small amount4 of wetting agent liquor soap” produced in t’he sulfate treatment of wood pulp itirring until complete coverdge was obtained. A series of s u c ~ ) ~ served as the water-soluble soap. To be incorporated in the mixes gave the upper limit of the area of coating. The l o ~ t r mix, a typical aggregate was prepared consisting of approxima,tely limit was obtained by a similar procedure, the wetting agent .io%, limeaione and 50% siliceous materials. It was carefully heing added first, followed by small amounts of activating ageii graded tmot h e following size analysis: Retained on a 1-inch On the basis of these experiments bIcLeod suggested a gener: mesh, 0%; on 3/4-mesh, 15%; on 4-mesh screen, 45%; on 30mechanism for the processes taking place during treatmeut mesh screen, 72.57,; on 200-mesh screen, 95%,. He pictured one valence of the metal ion in the activating agtril Empirically it was found that: (a) A ratio based upon chemiinteracting with the aggregate surface, leaving the otherb t I c‘id equivalents of aluminum sulfate t’o sodium oleate was the react with available fatty-acid radicals t o produce a film of 11) most saDisfactory, when both effectiveness of treatment and efdrocarbon chains which would be selectively wet by bitumen. ficient use of reagents were considered. ( b ) The commercial This explanation assumes t h a t the chemical mechanism of t i l t aggregate, presumably because of the large surface presented by treatment is restricted to a reaction on the surface of the aggruthe fine particles, required much more of the reagents than did the gate and does not consider that portion of the reactants whicakl uniform 0ttax-a sand (0.357, water-soluble soap on a n aggreproduced the colloidal, water-inqoluble soap in suspension; t’rir latter, in turn, TTas found t o play a significant role in the trrwtgate weight basis compared with 0.0570 on Ottawa sand). ( e ) Upon addition of t h e reagents the supernatant liquid becamv ment. milky and upon further mixing again became clear. The milky To clarify the situation several series of mixes weie made w i t Y l suspension was shown t o be a colloidal sol of aluminum oleatr. Ottawa sand and aluminum sulfate and sodium soap as reagenib The colloidal particles probably were adsorbed by t,he aggrezittr Their compositions are indicated by the points on the dottiid surface and built up a film of water-insoluble soap. Onvr lines in Figure 1. Strict observance was made of the necessity o r flocculated, the insoluble soap would not coat the aggregate a n d preventing preflocculation of the colloidal water-insoluble soap the treatment, failed. To avoid this the reagents had t o be a d d r d romplete rowrage rould he ohtained with any ratio, pi ovided
.
June, 1944
INDUSTRIAL AND ENGINEERING CHEMISTRY
that (1) reagents were present in sufficient concentration t o produce the amount of water-insoluble soap required for coverage when the proper 1 t o 1 ratio was used, and ( 2 ) the reagent in excess was added last. The explanation of the f i s t requisite was obvious, but for t h e second, less so. If excess aluminum sulfate were &-st added t o t h e mix, it flocculated t h e water-insoluble soap as formed; however, when t h e soluble soap was in excess, preflocculation should not have been a hazard. Other experiments showed t h a t the treatment, when applied t o silica, required the adsorption of a small amount of the activating agent before adsorption of t h e colloidal soap would proceed. This explained the need for adding the water-soluble soap last when present in excess; if added first it reacted with all of t h e activating agent before the required amount could be adsorbed. Further tests showed t h a t the treatment was effective on limestone without the preliminary adsorption of activating agent. McLeod also reported t h a t the salts of the alkaline earth metals, particularly those of calcium, did not function efficiently as activating agents, even when much larger amounts of reagents were used than was required with aluminum sulfate, for example. By taking care t o avoid flocculation of the water-insoluble soap, it was found possible t o obtain good coverage on Ottawa sand even with the calcium soaps in low concentration. TEST PANELS
To test the applicability of the treatment outlined, test panels were laid down during a week of heavy rains under conditions simulating those encountered in practice. Panels were made from a wet aggregate and three road oils (A, B, and a cracked product). It was first hoped t h a t three panels could be made from wet aggregate with each oil-a section without treatment, a section treated with Ivory soap as the wetting agent, and a section treated with soap made from tallol (the fatty acid obtained from black liquor soap). Coverage of t h e wet aggregate without treatment was so poor, however, t h a t a torch had t o be used t o dry the aggregate. Three untreated sections, t o be used as standards, were laid at a later date with dry aggregate. The solutions were made up in the field at the following concentrations: aluminum sulfate, 0.4 N ; Ivory soap, 0.1 N ; tallol soap, 0.2 N . These concentrations were chosen as the most efficient from t h e standpoints of conservation of water and ease of dissolution of reagents. As previously indicated, the full treatment was made in steps. The following scheme (with the mixer running, already loaded with aggregate) was found satisfactory: 1. Add one treatment sulfate solution. 2. Mix for 30 seconds. 3. Add one treatment soap solution. 4. Mix for 30 seconds. 5. Add half the total amount of oil to be used. 6. Mix for 45 seconds. 7. Repeat steps 1, 2, and 3. 8. Mix for 45 seconds. 9. Add the remainder of the oil. 10. Mix for 45 seconds. 11. Repeat steps 1, 2, 3, and 4 until coverage is complete. The amounts of reagent representing one “treatment” were, per 100 pounds of aggregate: 1 pint o f sulfate solution, 1 quart of tallol soap solution, and 2 quarts of Ivory soap solution. The values were chosen simply for convenience. Three and a half treatments of sulfate and soap were used. This schedule is presented t o bring out factors which must be (sonsidered in‘any attempt a t larger-scale application. Pretreatment, before t h e addition of oil, was made t o condition the fines for coating by bitumen. Thus, the f i s t half of the oil added went for this purpose. The extra 15 seconds of mixing before the addition of the second half of the oil served t o spread the &-st half as far as possible and start coverage on most of the aggregate particles. Since the mix was still lean, there was little danger of balling, and additional mixing at this point re-
587
duced the mixing required after all of t h e oil was preserit. The scheme outlined proved a means of obtaining good coverage, within a minimum time of mixing, without appreciable agglomeration of the coarse and fine particles. I n this phase of t h e work the necessity for smearing action in mixing became most evident. The standard concrete mixer, which simply raised the mixture and dropped it, was first tried and found t o give unsatisfactory results. Coverage was not much greater than SO%, and attempts a t longer mixing resulted in balling of the mix. A plaster-type mixer, with stationary horizontal shell and curved mixing blades mounted on a horizontal shaft, was then tried. This fulfilled the need for a smearing action and gave 90% t o complete coverage without appreciableagglomeration. I n general, the results from the initial adhesion standpoint were excellent. Heavy rains, which washed a great deal of oil from the untreated sections during the night after placement, caused no loss of bitumen in the treated sections. The untreated sections presented unsatisfactory surfaces largely because of these losses. This made sharp the comparison between treated and untreated sections.
T A ~11E 1. COMPARISON OF BITUMENADHESIONIN TREATEI) AND UNTREATED SYSTEMS (Mix consisted of 4% oil and Verona commercial aggregate, 600-gram sample) Oil A Oil B Untreated system yostripping in Riedel and Weber test H20 100 90 ‘/25d M NazCOa 100 100 % stripping in washing test Stage 1 25 25 Stage 2 100 100 Stage 3 100 100 Stage 4 100 100 Treated systema %qrip;;2go~del
‘/z M NazCOs 1 M NazCOa
and Weber teat
70stripping i n waahing test
5 25
60
0 ( s o h cloudy) 0 ( s o h c1oudy)t 0 ( s o h dark)
Stage 1 0 0 Stage 2 0 0 Stage 3 5 5 Stage 4 10 10 a Standard treatment with tallol soap a n d aluminum sulfate. b L/c M NazCOa solution.
During t h e fist eight months, in fall, winter, and spring weather, t h e treated panels held up satisfactorily, as did the untreated sections in which dry aggregate had been used. After a few weeks of exceptionally hot summer weather, however, treated portions of the road showed distinct evidence of lateral displacement or “shoving”. This shoving took place through the entire width of the matte and was more noticeable in surfaces with oil B than those with A. The panels were laid on a n old bituminous surface, impervious t o water, and the most pronounced failure occurred along a low edge where a longitudinal trough in subgrade had been filled. At these points the matte, when opened, showed a high moisture content. Both the treated and untreated road sections had t o be built up on this low side of the road so t h a t the matte reached a thickness of 5 inches in some spots, rendering these areas particularly susceptible t o shoving action. The untreated sections were relatively stable t o displacement. The panel containing oil B showed t h a t the asphaltic material had not really set. The matte had cracked badly and appreciable amounts of moisture were present immediately below the surface. This condition was not apparent in the untreated panels containing the same type of oil. Thus, in this case the chemical treatment may have affected the aging properties of the oil. A portion of t h e shoving observed probably could be attributed t o a n excess of bitumen in the mix and t o the high moisture content of t h e n a t t e .
588
Vol, 36, No, 6
INDUSTRIAL AND ENGINEERING CHEMISTRY LITERATURE CITED
In general, the research showed that bitiiminous materials could be made to coat water-wet aggregate t o produce a highly water-resistant mix a t a reasonable cost by :t modified i\/IcI,eod type of treatment. As developed, the treatment may have possibilities for application in road construction where unifolmly thin mattes can be laid and adequnte drninage assured. In special applications where a water-resistant mixture of bitumencoated aggregate is desired and where the plastic propertie? of t h e mass is not a problem, the treatment should be useful. Further research may point the way toward more general application.
Uijkstra, F. (to Shell Development Co.), Cntiadiau Patent 406,399 (1942). Dohxe, H., and Spoun, F. (to I. G. FaIbeniiidustrie), U.8. Patent 2,191,293 (1940). Il’in,B., 2. physiie. Chem., A155,403 (1931). Johnson, J. M . , U. S. Patent 2,177,568 (1939). McCoy, P. E. (to Am. Bitumuls Co.), Ibid., 2,313,759 (1943). Mack, Charles, J . Soc. Chom. Ziad., 60, 111 (1941). McLeod, N. W., ilssoc. Asphalt. Paving Tech., PTOC. Tech. Sffiysions, 9, 1 (1937). N. V. de Bataafsche Petroleum Ma.atsoliappij, Dutch Patent 51,212 and Brit. Patent 533,170 (1941). Pfeiffer, J. P. (to Shell Development Co.), U. 8. Patent 2,225,570 (1940). Roediger, J: C . (to Standard Oil Development Co.), Canadian Patent 405,350 (1942). Standard Oil Development Co., Rxit. Patent 533,927 (1941). Ibzd., 545,287 (1942). Whitacre, C. H. (to Standard Oil Co. of Ohio). U. S. Patent 2,286,244 (1942).
ACKNOWI.EDG.\lFLYT
This work was done under the joint qmiisor4iip of the tVi+ consin State Highway Commission, thc Wisconsin Alumni Research Foundation, and the Cniversity of Wisconsin. Man!, persons gave valuable aid and advice during the course of the work. J, W. Williams, 0. A. Hougen, and Joseph Zapatn ,deserve particular mention. More complete details are t o be found in the Ph.D. dissertation of the author, submit,tod to t h r facult>pof the University of Wisconsin in ,lune, 1940.
Winterkorn, H. F., IND.Ena. CHEM.,26,815 (1934). Ibid., 30, 1362 (1938). Winterkorn, H. F., Assoc. Asphalt Paving 7%&., P ~ o c .T e d Sessions, 9 03 (1937).
f L
NITROBENZ
H. Milton Woodburn, Keith Smith, and Hyman Tetewsky T H E UNIVERSITY OF BUFFALO, BUFFALO, N. Y .
I\’ RECENT years much progress has been made in establish-
I
ing relations between structure and physical properties, or among various physical PI operties---for example, two papers by Francis (4, 6). To fortify and test such correlations it is important that as many properties as possible be included. Critical solution temperatures are not often considered except in the one case of “aniline points” for hydrocarbons. Therefore, a btudy was undertaken of other critical solution temperatures. The results are here reported for the critical solution temperature of ten paraffins with nitrobenzene and of six paraffins with ,S,,S’-dichloroethyl ether (Chlorex). No record of the critical solution temperatilies of paraffins with &@’-dichloroethyl ether has been found, although this solvent has been used for the extraction of certaiii petroleum fractions (9). The critical solution temperature%of paraffins with nitrobenzene have been determined for a relatively small number of hydrocarbons (1, 3, 6, 8,10, 11, 1 2 ) . I n cases where more than one figure has been published, it is apparent that some of them are 01 doubtful value. Table I lists these recorded values. For comparison the data obtained in thib work are given, as well as values for the critical solution temperatiires of the parafhns with aniline. WETHOD
These critical solution temperatures weie tlr~eiImried in sealed glass capsules made from 9-mm. Pyrex tubing, 8-10 mi. long. Reasons for using this technique were ( a ) to allow the use of small samples of pure hydrocarbons difficult to obtain, ( b ) to prevent evaporation and loss of volatile hydrocarbons during the determination, and ( c ) to allow repetition of the measurement as often
as desired without, t,he possibility of contanfiiation by water absorption. Agitation duririg t,he determination was accomplished by magnetic stirring. A headless nail, about 3 cm. long and sealed i n glass, was placed in the capsule before introduction o f the liquids and sealing. The sealed capsule was fastened by a short length of rubber tubing to a glass holder arid inserted into the hollow tube of an electromagnet (Figure 1). The latter was made by niriding KO.24 13. & S. gage, cotton-sheathed copper wire around a t,hin-walled, l/,-inch iron pipe for a length of 4 cm. and a depth of 1.5 cm. Variable resistances were placed in series in the circuit t,o control the strength of the electronlagnets, and a circuit breaker (Diamond flash button, made by Eagle Electric Manufacturing Company, Inc.) was included t o tnrn the current 011 and off ttutomatically. Placement of the capsule relative to the electromagnet was such that the covered nail was pulled up through the interface and allowed to drop by gravity while the current was ofl. Very efficient stirring resulted. A by-pass in the circuit allowed the flasher to be cut out., leaving t,he magnet energized and holding the bob up, so that an unobstructed view ~
~~~~
~
~
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T h e critical solution temperatures of ten paraffin hydrocarbons w i t h nitrobenzene and six w i t h 6’,8’-dichloroethyl ether have been carefully determined. Several values recorded in t h e literature are shown t o be i n error. Among t h e normal paraffins, as t h e number of carbon atoms increases, t h e numerical difference between t h e critical solution temperature and t h e aniline point shows a steadily increasing value for nitrobenzene solutions and a steadily decreasing value for p,B’-dichloroethyl ether solutions.
