-Resources had assets of less than $1,000,000 and 63% had assets of less than $4,000,000. Among the private placements this company had made were loans for as small an amount as $25,000. SECURITY DEALERS
Security dealers and the markets they create and maintain by their activities constitute another major group of financial institutions that pull together savings and channel them into productive uses. Data provided by the National Association of Security Dealers show 241 dealers domiciled in the South Atlantic States. Many of these firms, of course, have branch offices in the principal cities of the area. In 1953 this group handled private corporate underwritings, including private placements for which they acted as intermediaries, totaling $193,000,000. The exact disposition of the securities is, of course, unknown, but it is fairly safe to assume that the bulk of them was sold to investors living in this region. Last year, for example, a Richmond dealer managed an underwriting group that had no trouble in disposing of a $4,000,000 issue of bank stock to investors in the State of Virginia. I n fact, most of the dealers would have been glad to have received larger allocations of the total issue. The $193,000,000 of securities underwritten by the region’s dealers in 1953 represents a large increase over the $24,000,000 underwritten in 1940. This growth was due to an increase in the number of dealers in the area-an increase of 27% between 1940 and 1953-and to more aggressive action on the part of the dealers in participating in the financing of local business. OTHER FINANCIAL INSTITUTIONS
In addition to banks, insurance companies, and security dealers, the South Atlantic region has the same variety of money dealers that is found in other sections of the country, You will find here mutual savings banks, credit unions, savings and loan associations, sales finance companies, mortgage companies, industrial banks, trust companies, consumer loan companies,
pension trust funds, and mutual funds, not t o mention the wide assortment of Government agencies for lending or for insuring or guaranteeing loans made by private lenders. Among these secondary institutions the growth of savings and loan associations has been particularly great in the South Atlantic region. The resources of these institutions have grown from about $500,000,000 in 1929 t o more than $3 billion a t the end of 1952. They have more than doubled their share of total savings and loan assets in the country, increasing from 6% in 1929 to 13% in 1952. The largest association in the nation is located in the region, and of 39 companies in the country with assets of $35 million or more, nine are located in the South Atlantic States. These firms limit their lending almost entirely to individuals acquiring homes, but they are another mark of the growing availability of funds in the area. Industrial development corporations such as those of the New England States have been of negligible importance in the financial resources picture of the South Atlantic States, and there is no strong indication that this situation will change. CONCLUSION
The marked growth in the financial resources of the South Atlantic region is both a cause of and a result of the fundamental changes that have occurred in recent decades in the economy of the area. T h e declining relative importance of agriculture and the dynamic industrialization of the area have contributed t o a substantial improvement in income levels. That, in turn, has provided the basis for the expansion of South Atlantic financial institutions, generally a t a faster rate than in the nation as a whole. The region’s financial resources are of course not adequate in every respect. The important fact is that the financial institutions of the region have had marked and sound growth with a very definite improvement in their ability to finance the expanding business activity of the region. RECEIVED for review September 13, 1954.
ACCEPTED November 20, 1954
Reprints of this symposium may be purchased for 75 cents each from the Reprint Department of the American Chemical Society, 1155-16th St., N. W., Washington 6, D. C.
Phase Changes in Soap-Oil Dispersions B. W. HOTTEN AND D. H. BIRDSALL Calgornia Research Corp., Richmond, Ca1;f.
D
ISPERSIONS of soaps in nonaqueous liquids are commercially important in the form of lubricants, gelled fuels, surface coatings, and waterproofing agents. The present investigation was concerned primarily with plastic dispersions of soaps in oils in the form of lubricating greases, but the method of study used is applicable to other solid-liquid dispersions as well. Complete phase diagrams were obtained by Vold and Vold (9) for a limited number of soap-oil systems. These consisted of lithium and sodium stearates in Decalin and in cetane. Phase boundaries were established by observations under polarized light and in an x-ray diffraction camera. In the present investigation, a simple method was sought of establishing major phase relationships which could be used for a wide variety of dispersions. When soap-oil systems are heated,
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a modification in properties of the individual components is t o be expected as well as a modification in their relationship t o each other. Thus, the viscosity of the oil will decrease; the soap particles may soften, expand, and split apart; and the absorption of oil within the soap particles may increase. In most systems, the soap will finally dissolve completely in the oil. It was thought that the more important changes of this type would be reflected in the differing rate of separation of the oil from the soap over a broad temperature range, and a simple vacuum filtration technique was used t o measure this property. Previous studies of separability of grease components have been made with the aid of special pressure filtering devices. Herschel (3) devised a press to separate the oil from greases through a filter paper membrane. He found that the separation rate of the oil
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increased with decreasing viscosity and with increasing temperature (a temperature range of only 20" t o 110" C. was investigated, however). Farrington and Humphreys (W), working with the same type of filter press, obtained further information on the effect of oil viscosity on filtration rate and also determined the effects of grease consistency, filtration pressure, and soap type. Roehner and Robinson (8)further studied the effects of soap type, soap concentration, oil viscosity, and temperature (maximum 55' C. ) by filtration under pressure through fritted-glass inembranes.
Figure 1.
Filtration rate of 14% grease at 150' C.
lithium stearate
Vol. 47, No. 3
69% paraffinic, 28% naphthenic, and 3% aromatic carbon atoms with average molecular weight 430 and viscosity of 114 cs. a t 38 C. GENERAL OBSERVATIONS
Typical soap-thickened greases pass through three principal phase regions with increasing temperature At moderate temper atures, they exist as pseudogels or microcrystalline pastes, which consist of networks of soap crystallites in oil. Electron niicroscopic examination of various greases by Farrington ( 1 ) and Hotten ( 6 )and of lithium soap dispersions in particular by Hotten and Birdsall (6) have revealed the morphological nature of the crystallites. The most frequently observed shape was rodlike, about 0.1 micron in diameter and 1 to 10 microns long. More nearly spherical and longer, threadlike crystallites mere also observed. These crystallites evidently form a reticular framework which contains the oil phase by capillary forces. Application of a vacuum through a membrane to such a structure causes the oil to drain away a t a rate dependent upon the form and arrangement of the crystallites and the viscosity of the oil. Although the soap from greaselilre dispersions is particulate when diluted and washed free of oil for microscopic examination, the crystallites must cohere sufficientlv in the whole dispersion to account for the rigidity observed, both in the dispersion and in aerogel skeletons left when oil is removed under conditions avoiding meniscus formation ( 7 ) .
The present study had the specific objectives of ( I ) simplifying and standardizing a liquid-separation technique, ( 2 ) broadening t h e temperature and compositional ranges over those of previous studies, and (3) interpreting liquid separability differenres in terms of fine structural differences in the dispersions. EXPERIMENTAL PROCEDURE
The test equipment consisted of a 150-ml. Buchner funnel (Coors No. 2) fitted with Whatman No. 2 filter paper and a 250ml. suction flask, which was modified by replacing the existing side arm with a spherical glass joint. Glass connections within the oven thus permitted high-temperature operation. Cork stoppers are sufficiently heat-resistant a t temperatures as high as 200" C. for use as connectors between the funnels and flasks. For still higher temperatures! glass Buchner funnels may be used and connected to the suction flasks with ground glass joints. The dispersion to be tested .was first weighed (100 grams) into t h e Buchner funnel, after which the assembly was placed in a n oven and preheated for 2 hours a t the test temperature. At the end of the preheating period, the pressure in the suction flask was reduced to 130 mm. of mercury and held there 3 hours. This filtration period was selected on the basis of the filtration-time curve shown in Figure 1, which indicates considerable leveling off in oil separation rate after 2 to 4 hours. The filtrate was then weighed. The gross weight of the assembly was determined before and after filtration, so that evaporation losses could also be taken into account. Reproducibility of filtrate meights from replicate samples was generally good. Filtrates were aIso analyzed for soap cations or other appropriate elements as a measurement of variable solubility. The soaps were made in situ, except for the aluminum soap, by adding the metal hydroxide dispersed in water t? a solution of the fatty acid in oil, heating to 200" C. with stirring, pouring out into a shallow pan to cool, and milling the resulting gel through an 80-mesh screen. Aluminum soap dispersions were made by addition of aluminum nitrate solution to the appropriate potassium soap dissolved in water, followed by filtration, washing, and drying of the resulting precipitate, which was then heated in oil, as described above. The fatty acids were of Eastman White Label grade, except as noted; and metallic bases and salts were Baker's C.P. Final soap concentrations were 12% by weight, except as noted. Two hydrocarbon oils were used as dispersion media: The "naphthenic oil" was an acid-treated California naphthenic pale oil giving a carbon group analysis of about 40% paraffinic, 37% naphthenic, and 23% aromatic carbon atoms with average molecular weight 340 and viscosity of 100 cs. a t 38" C.; the "paraffinic oil" was a solvent-treated California paraffinic neutral oil giving a group analysis of about
% IO
10 MICROCRYSTALLINE PASTE
Figure 2.
GEL
d
SOLUTION
Effect of temperature on oil fluidity and grease filterability 14 70lithium stearate-naphthenic oil grease
As the temperature rises, the oil becomes less viscous and consequently drains more rapidly away from the soap network, as shown by the initial steeply rising portion of the lithium soap dispersion curve in Figure 2 . (The difference in filtration rate a t the same temperature in Figures 1 and 2 is probably due to the fact that a commercial soap was used for the curve in Figure 1and pure laboratory products n'ere used for the curve in Figure 2 and subsequent experiments.) -4fluidity-temperature curve of the oil used t o prepare this dispersion is shown in the same figure. There is no evidence of a phase change up t o 150' C. and spectroscopic analysis of filtrates indicates the absence of dissolved soap below this temperature, which was taken t o be the maximum for the pure microcrystalline paste regime. As the temperature rises still higher, gelation occurs. The oil is now held more tightly by the soap, as shown by the rapid drop in the filtration curve a t 150" to 175" C.; the point of maximum gelation is taken to be 175" C. in this case. The exact nature of the gel structure will probably remain unknown until soap-oil dispersions can be successfully examined in the electron microscope at the gelation temperature. But the summation of changcobserved on gelation-reduced oil separability, increased optical
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clarity, and increased elasticity-indicate formation of a finer and more highly coherent structure. If the crystallites swell, they become more porous and thus entrap oil more tightly than in the microcrystalline paste. This may result from a splitting apart of crystallites into bundles of finer fibrils, as illustrated in Figure 3. These gross changes possibly result from rotational transitions ( 4 ) within the soap crystallites, but further experimental
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be expected t o increase with increasing crystallite size. This correlation is roughly observed, a s may be seen by comparison of the crystallite dimensions of Table I, obtained by electron microscopic examination, with the separability rates a t .50° to 100' C. shown in Figure 4. The larger, rodlike crystallites of lithium and calcium stearate led t o higher separability than the finer ones of sodium (rodlike) and aluminum (spherical) stearates. Phase changes in this series were checked by analyses of filtrates, which were found t o contain no detectable soap below the gelation temperatures (except for aluminum distearate), and only traces in the gelatinous regions, and t o have the same composition as the whole grease above the dissolution temperature. Solubility-temperature curves are shown in Figure 5. Anion Variation. The effect of anion modification in lithium soap dispersions is shown in Table I1 and Figure 6. T h e lithium
GEL
Figure 3. Postulated structures of idealized soap crystallite matrices in microcrystalline paste and gel phases Swollen crystallites in gel may reduce oil separability by both internal absorption and restriction of interstitial openings
work is needed t o test this possibility. An alternative possible mechanism of gelation involves a thinning out and fusing together of the crystallites to form a honeycomb of cells containing the liquid phase, such as Wyckoff (IO)found in aqueous gelatin gels. Returning t o Figure 2, we see that an increase in temperature above t h a t causing gelation is reflected in a second ascending slope. Analysis of filtrates obtained a t such temperatures shows rapidly increasing soap solubility. At 10' t o 25' C. above the maximum gelation temperature, the filtrate usually had the same composition a s the whole grease. The general characteristics of the oil separability curves showed the following changes with compositional variation. COMPO SITION A L VARIATIONS
1
Figure 4. Effect of cation variation on vacuum filtration rate with varying Cation variation among stearate soaps, anion variation among temperature lithium and sodium soaps, and oil variation in lithium and 12 70stearate soap-naphthenic oil greases aluminum stearate dispersions were examined. Cation Variation. One of the most important factors which alter t h e shape of filTable I. Effect of Cation Variation on Structure and Phase Relations of Metal t r a t i o n curves is t h e soap Stearate-Naphthenic Oil Dispersions cation, as shown in Table I Consistency Phase Regions, C. and Figure 4. Among the Average ASTM D 2171-48 Crystallite Dimensions, fi Worked MicrocrystalMaximum Complete four stearate dispersions (made Cation Diameter Length Penetration, Dm. line paste gelation solution from Atlas Hystrene 97, 9793 180 >205 < 150 Lithium 0.13 1.3 311 >200 135 < 100 120 Calcium (hydrated) 0.2 4 294 has the highest gelation and 95 Aluminum (distearate) 0.1 ... 269 (spherical) dissolution temperatures and aluminum stearate the lowest. Table 11. Effect of Anion Variation on Structure and Phase Relations of Sodium stearate has an unLithium and Sodium Soap-Naphthenic Oil Dispersions usually pr o l o n g e d g e l a t i o n Consistency, Phase Regions, C. region and low oil separaAverage Crystallite ASTM D 217-48 ~ i ~ ~ ~ Dimension, fi Worked crystalline Maximum Complete b i l i t y e v e n i n t h e micropaste gelation solution Anion Diameter Length Penetration, Dm. crystalline p a s t e region. Lithium aoaps Laurate 0.3 1.3 310
