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INDUSTRIAL AND ENGINEERING CHEMISTRY
octane number versus engine-speed curves for these blends. Corresponding laboratory octane ratings of the blends and their components are shown in Table VI. Although the Polyform distillate has a lower basic octane number, the higher singlepass gasoline yield from polyforming makes this blend richer in cracked distillate than the blends containing the catalytically cracked gasolines. The road performance curve for the unleaded Polyform blend falls between those for the two blends of catalytically cracked gasolines and is parallel to them. The higher concentration of cracked distillate in the Polyform blend gives this blend slightly lower lead susceptibility than the others. The yield of the Polyform blend based on crude, however, is considerably higher. CATALYTIC TREATING
Polyform distillate can be catalytically treated in conventional catalytic-cracking equipment to produce a satisfactory base stock for 100/130 grade aviation gasoline. Table VI1 shows octane numbers and inspections for several typical Polyform distillates before and after catalytic treatment. The naphthas charged to the Polyform unit represent three crude sourcesEastern Venezuela, mid-continent, and East Texas. The yields and quality of the aviation base stock produced are similar from all crude sources. The bromine number in all cases was reduced to a sufficiently low value to meet the requirements for aviation gasoline blending. Aviation octane numbers of the treated base
423
stock are raised to a level where approximately 20 volume yo of alkylate will produce a finished fuel with a 1-C octane number of 100 and a 3-C rating of S f 1.25 or higher. Either a debutanized or a depentanized Polyform distillate may be catalytically treated, but the highly olefinic CC and CS fractions from the Polyform operation are normally used as charge stocks for alkylate production. While Polyform distillates of 76 or higher octane number show good treating characteristics, conventional thermally cracked distillates do not produce good base stocks by catalytic treatment because of their inherent low quality. LITERATURE CITED (1) Am. SOC.Testing Materials, test procedure D 484-40. (2) Francis, A. W., IND.ENQ.CHEM.,18,821 (1926). (3) Grosse, A. V., and Waokher, R. D., IND.ENQ.CHEM., ANAL.ED., 11, 614 (1939). (4) Offutt, W. C., Ostergaard, P., Fogle, M. C., and Beuther, H., Oil Gas J., 45, 180-8 (1946); Proc. Am. Petl-oleurn Inat., 26, 111,222 (1946). (5) Offutt, W. C., Ostergaard, P., Fogle, M. C., and Beuthel, H., Petroleum Processing, 2, 753 (1947) ; Oil Gas J . , 46, No. 21; 809 (1947). (6) Offutt, W. C., Ostergaard, P., Fogel, M. C., and Beuther H., Proc. Am. Petroleum Inst., 26, 111, 237 (1946). (7) Risk, T. H., and Jordan, J. F., Petroleum Refiner, 26, 99 (April 1947) ; Oil GUSJ . , 45, NO.4 8 , 7 8 4 8 (1947). RECEIVED October 3, 1947. Presented before the Division of Petioleurn Chemistry at the 112th Meeting of the AMERICAN CHEMICAL SOCIETY,New Y o l k . N. Y.
Evaluation of Ternary Mixtures SYNTHETIC DETERGENT-SOAP-BUILDER J. J. MORRISROE' AND R. G. NEWHALL Oronite Chemical Company, Sun Francisco, Calif. T h e pH, foaming, and detergency of a variety of binary mixtures have been studied. These mixtures include both soap-builder combinations and synthetic detergentbuilder combinations. The ternary system sodium steaate-synthetic detergent-tetrasodium pyrophosphate has also been investigated. It has been found that such mixtures when used in hard water may be so proportioned as to exhibit either high detergency and high foaming or high detergency and low foaming.
M
investigators have studied the synergistic effect of electrolytes, or builders, on the foaming and detergent properties of both soaps and synthetic detergents. For example, Harris, Eck, and Cobbs (5, 11) have made an extensive study of the detergency of a commercial medium titer soap when built with alkalies, both singly and in combination. Harris (9, 10) has similarly investigated the effect of builders on a typical synthetic detergent While the effect of such electrolytes when used with a single detergent is well known, there seems to have been a general belief that soaps and synthetic detergents are mutually incompatible, or a t least confer no benefits when used in combination. Thus Vallance ($0) reports that combining synthetic detergents with soap often tends to decrease rather than increase cleansing properties and may inhibit lathering. Harris (8) during an extension of his previous work, briefly examined mixtures of soap and synthetic detergent and concluded that there was evidence of synergistic action in only one out of six cases. 1
Present address, Purex Corporation, South Gate, Calif
McDonald (15), it is true, reports that the detergency of 0.5% sodium stearate in hard water was improved markedly by the incorporation of salt-free synthetic detergents, but he apparently undertook no systematic investigation of such mixtures. It is the purpose of the present study to examine the effect of electrelyte builders on mixtures of synthetic detergent and soap. It has been shown that such ternary mixtures possess properties that cannot be equaled with binary mixtures of soap-builder or synthetic detergent-builder. The synthetic detergent used was a representative sample of a commercial product containing 40% active ingredient (an alkyl aryl sulfonate of approximately 352 molecular weight) and 60% sodium sulfate. Since sodium sulfate is itself a builder, as has been shown by Harris (8), the systems considered here, strictly speaking, consist of one more component than the name would indicate. However, sodium sulfate and added electrolyte together have been considered as the builder component in order to somewhat simplify the terminology. Sodium stearate wa': chosen rather than any of the commercially available high-titer soaps as it was desirable to employ a material of known and constant composition. This compound may be considered as typical of a pure soap in all essential properties, except that its solubility is somewhat lower than that of most commercial soaps. However, the relative value of the results is not altered significantly by the fact that the stearate may be present in colloidal form rather than in true solution. Because the action of builders, especially with soap, is far more apparent in hard water than in soft, water of 300 parts per million hardness (200 as calcium and 100 as magnesium) was used in all tests so that the effects might
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be defined as clearly as possible. This artificial hard water is essentially the same as that employed by Harris and his coworkers in their investigations. While the properties desirable in a detergent mixture are many and varied, it is well recognized that three of the most important are detergency, foaming, and pH. The majority of investigators in this field have measured one or more of these qualities, and this work similarly was limited to these three nieasurements.
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ally that the presence of cloth and soil, especially soil of an oily type, may alter sudsing significantly. However, the relative values are sufficiently accurate for the present purpose. Furthermore, the lower foam values recorded should approach rather closely those observable in practice.
METHODS
The pH measurements were made with a Beckman Model G laboratory pH meter a t 25' C. (77' F.) in hard water. KO correction has been made for sodium ion error. Therefore the higher values are slightly inaccurate but not significantly so for the present purposes. As yet there is no standardized method of measuring the foaming properties of solutions. Harris and his eo-workers (5, 9, 10, 11) estimated the quantity of foam during the washing, but such a procedure cannot give accurate and reproducible results. Merrill and hloffett (14) describe two methods of measuring foam stability. In one of these the rate of drainage of liquid from a foam produced by air blowing is measured, and in the other the rate of area decrease of a foam monolayer is determined. Neither of these methods, however, is well suited to the study of stable foams such as are considered here. TWOfederal specifications (2, 3) call for the determination of lathering ability by hand-shaking a solution in a graduated cylinder and measuring the volume of the resulting foam. While such a makeshift procedure approximates actual conditions of use, it suffers from an obvious lack of reproducibility because of the human element involved. In these studies the method of Ross and I Miles (I?'), was ernso cms. ployed: this method was found to be simple and rapid and t o give results of good reproducibility. 7 mm. Ross and Miles give a 1 detailed description of their apparatus and method and an outline only will be given here. Figure 1. Pour Test Apparatus In this apparatus (shown in Figure 1)I foam is produced by the impact of the solution falling a fixed distance from t,he upper reservoir into the liquid at the bottomof the cvlinder. In use the cylinder is set up and adjusted to the vertical, and n-ater at 43.3" C. (110" F.) is circulated t'hrough the outer jacket' b,y means of a centrifugal pump. The dry ingredients then are dissolved in 300 ml. of hard water with mechanical stirring, and the solution is aged in a thermostat at 43.3" C. (110' F.) for 10 minutes. At the end of the aging period 50 ml. or solution are pipetted carefully into the cylinder. The liquid is allowed t o run d o m the wall of the cylinder, both to wet it thoroughly and to ensure that no foam is formed in the bottom. The upper reservoir then is filled with 200 ml. of solution and placed in position, a,nd the stopcock is opened. As soon as the reservoir is empty, the height of the foam in millimeters above the liquid surface is measured. If care is taken t o have the apparatus scrupulously clean and to prepare and age all solutions in an identical manner, the results are reproducible to .ivithin 4 or 5 mm. It should be recognized that results obtained by this procedure will not correlate necessarily with sudsing observed under actual conditions of use. It is known gener-
Figure 2. Launder-0-Meter Jar and Rubber Agitator Balls
The subject of detergency testing is one which has received attention from many investigators. Heron (12) gives a review of the various washing tests which have been employed. IIe mentions the difficulties encountered by previous workers, and in particular points out the objections to methods dependent on n-eighing the cloth to determine the amount of soil removed. Ile then describes a procedure which is essentially similar t o that employed by Rhodes and Brainard (16) much earlier. Briefly, the method consists of artificially soiling cloth, making the cloth into bags filled with glass beads, and then washing these bags in a revolving cylindrical drum by a standard procedure. The soil removal is measured with a suitable reflectometer. Various other methods have been used. Bureau of Ships specification 51947 (4) requires the washing of artificially soiled swatches distributed throughout a normal load of soiled clothing in commercial laundry equipment. While such a method probably approaches actual conditions of use more nearly than any other, it is hardly suitable for laboratory investigations when close control of the variables is required. Other specifications ( 2 , 15) require the washing by hand of artificially soiled cloth. The main objection here is t o the high amount of labor necessary. Rucltman, Hughes, and Clarke (18) describe a method of eualuating salt-water detergents by the mechanical washing of artificial soil from painted panels. Although this procedure should give adequately reproducible results, no correlation has been demonstrated between the ability to wash such panels and the ability to wash soiled clothing. If the efficiency of a detergent is to be measured by actually washing soiled cloth (and no simpler test has yet been devised), a procedure and apparatus must be employed which will give adequate control of the variables affecting detergent action. Bacon and Smith ( 1 ) consider these variables to be: the detergent; mechanical force; time; temperature; eaSe of soil removal; and soil suspension and redeposition. The standard Launder-0-Meter (manufactured by the Atlas Electric Devices Company, Chicago, Ill.) permits close control of several of these variables, as well as permitting a number of determinations to be made simultaneously. The soiled swatch is placed in a glass jar together with the detergent solution and a number of steel or rubber balls (Figure 2). Twenty of these jars then are clamped in position on the rotor, which revolves at a fixed speed in a constant temperature bath (Figure 3). In this way the mechanical force and the temperature are both controlled. Soil redeposition may be kept t o a minimum by having a sufficiently large ratio of solution volume to cloth area. Preliminary tests, in which a piece of unsoiled cloth was placed
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INDUSTRIAL AND ENGINEERING CHEMISTRY
425
in the jar with the soiled cloth, indicated t h a t under the conditions employed soil redeposition was so small as to have no significant effect on the results. The ease of soil removal, of course, IS governed by the nature of the soil used. Investigators in this field have used a wide variety of artificial soils; some of them, such as that required in Bureau of Ships specification 51847 ( d ) , have a large number of components. However, there is no apparent advantage in using such a mixture, and the soiling procedure is greatly complicated thereby. Since it was desired to determine soil removal by measuring the reflectance of the cloth, lampblack was employed as the major constituent. Animal and vegetable fats and oils and mineral oils are common constituents of the usual soil, and Figure 3. Launder-0-Meter Jars with Detergent Solution, Soiled Cotton Swatch, and Rubber Balls Ready for Washing Operation for this reason tallow and white mineral oil were included in our composition. The resulting mixture was similar t o that using a green tristimulus filter in order that the meter readings used by Bacon and Smith (Z), Rhodes and Brainard (Z6), and Flett might be numerically equal to the tristimulus Y values. Tho ( 7 ) , with one important difference. These workers used a relainstrument was standardized before each use against a white tively light soil, but preliminary tests showed that under our enamel plaque having a reflectance of 74.5Y0 relative to magwashing conditions such a soil was almost completely removed nesium oxide. The reflectance of each swatch was measured in by many detergent mixtures. Therefore, a heavier soil, which three places, with two thicknesses of similar cloth beneath to would not be completely removed, was used so that the differavoid variations due to transparency. The three readings, which ences between the detergent mixtures might be defined sharply. varied by about lY0, were averaged t o obtain the reflectance of Figure 4 shows unsoiled, soiled, and washed pieces of cloth, and the swatch. illustrates the degree of soiling employed. Several methods have been proposed for arriving a t a numerical Indian Head cotton cloth (obtained from the Nashua Nanumeasure of detergency. Flett ( 7 ) in his early work, using a facturing Company) TYas washed in 0.3% Calgon (sodium hexaLaunder-0-Meter for the washing of wool, employed qualitative metaphosphate) solution for 2 minutes a t 48.9' C. (120" F.). comparisons and did not attempt t o obtain numerical relations. I t then was rinsed in distilled water, air dried, and cut into Harris' method-a critical review of this method by a substrips 20.3 cm. (8 inches) wide and 9.1 meters (30 feet) long. committee of the A.S.T.M. has been reported by Crowe (6)The following soiling solution was thoroughly mixedand placed in a requires the removal of a strip of fabric after each one of four steel tank: 20 grams of acidless tallow; 72 grams of white mineral washings. The reflectance of these strips is measured on a scale oil; 8 grams of lampblack; and 3785 ml. of carbon tetrachloride. in which the reflectance of unsoiled cloth is taken as 100% and The cloth was passed through this solution a t a uniform rate, that of soiled cloth before washing as zero. The test is run in emerged vertically and passed between two batteries of infrared duplicate, and the reflectances of the eight pieces of cloth lamps, and then wound on a drum. After drying overnight, the removed during the washing are averaged to give a per cent soil cloth was rinsed in water a t 0" C., again air dried, and cut into removal. The values so obtained are used as measures of deterpieces measuring 5.1 X 10.2 cm. (2 X 4 inches). A new batch gency. of cloth was made up weekly t o avoid variations due t o aging. This procedure gave a soiled cloth of good uniformity. For example, the average reflectances (measured as described below) of the first 20 swatches from three successive batches of cloth were 20.870, 19.87',, and 22.5y0. The arithmetic means of the deviations from the average within each batch were 1 0 . 8 , 1 0 . 4 , and *0.6, respectively. I n performing the washing tests, a piece of cloth was placed in a pint jar together with ten 6.4-mm. (0.25-inch) steel balls and 100 ml. of detergent solution preheated to 60" C. (140" F.). The jars were placed in position and rotated for 20 minutes at 60" C. (140" F.) and 42 r.p.m. A total of four such washes was given, using a fresh 100-ml. portion of preheated detergent solution each time. The washes were followed by two 10-minute rinses with 200-ml. portions of preheated hard water. The strips then were removed and hung on a line to dry overnight. Each test was run in duplicate and the results averaged. This procedure is similar t o that which was employed by Harris, and which has been examined in some detail by Crowe (6). A B C To determine the amount of soil removed, the reflectance of the cloth before and after washing, as well as that of the unsoiled Figure 4. Cotton Cloth Used in Launder-0-Meter cloth, was measured with a Photovolt reflectometer, Model 610, ( A ) New cloth; (B) soiled cloth; ( C ) waehed cloth
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Figure 5.
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pH of Sodium Stearate-Phosphate Builder Systems
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Figure 7. pH of Synthetic Detergent-Phosphate Builder Systems
This procedure, as well as those employed by other investigators, implies that detergency is defined as the increase in visually apparent whiteness of the cloth, and this meaning has been used in the present work. Such a definition of detergency is reaaonable when, as in the present case, the effects under investigation are those which would be apparent to the average user of washing compositions. However, it should bc rccognized that methods based on this definition do not give a direct measurement of the actual quantity of soil removed. Such a measurement would be obtained only if reflectivity were a linear function of the quantity of soil present. Bacon and Smith ( 1 ) have pointed out that in general this is not the case; the results obtained in the course of the present work, which are in agreement with the findings of Utermohlen and Wallace ( I Q ) , indicate that the relation is actually logarithmic. As mentioned above, the apparatus used to measure reflectance gives a reading directly in terms of the tristimulus Y value, which in turn is so defined as to be a direct measure of apparent brightness. Therefore, for purposes of this study detergency is defined as the per cent increase in reflectance as measured with this equipment. This increase in reflectance is given by the difference between the reflectance of the washed and unwashed cloth, divided by the difference between the reflectance of the soiled and unsoiled cloth, as in the following equation: Detergency = Rs ___ - R2 x 100 Ri - Rz where I& is the reflectance of the unsoiled cloth; RZ is the reflectance of the soiled cloth before washing; and R3 is the reflectance of the soiled cloth after washing.
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Figure 8.
Detergency of Synthetic DetergentPhosphate Builder Systems
To detect any errors caused by variations in the soiled cloth or in the washing procedure and to provide for a measurement of reproducibility, a reference standard was included in each Launder-0-Meter run. This standard consisted of duplicate swatches washed in 0.201, sodium stearate solution. As an example of the variations encountered during the course of this work, the reference standard in twelve runs picked at random (employing several different batches of soiled cloth) showed detergencies of 20, 18, 16, 21, 18,21, 16,18, 23, 22, 22, and 17, with an average of 19 and a mean deviation of 2. Similarly, a series of eight rune using 0.2% synthetic detergent (employing six different batches of soiled cloth) gave detergencies of 38, 42, 41, 44,43, 40, 31, and 29, with an average of 38.5 and a mean deviation of 1. The average variation, therefore, was approximately 10%. DISCUSSION OF RESULTS
Binary Mixtures. The effect of phosphate builders on sodium stearate was studied first. Both trisodium phosphate and tetrasodium pyrophosphate were used in various proportions, while the concentration of total solids was held constant throughout the various series. Figure 5 shows the pH of such mixtures and indicates, as might be expected, that trisodium phosphate gives solutions of considerably greater alkalinity than does tetrasodium pyrophosphate. It will be noted also that with the higher proportions of tetrasodium pyrophosphate the $3. varies only slightly with the total concentration. This is t o be expected as the hydrolysis of the pyrophosphate is small. The curve for tetrasodium pyrophosphate at 0.29$$ concentration exhibits a distinct minimum a t a ratio of approximately 10%
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builder. It is possible that the explanation of this fact may be found in a consideration of the various equilibria which exist. With solutions in hard water, i t will be seen readily that there are five such equilibria, M follows:
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0.2% Tot21
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Tetrasodium Tetrasodium Pyrophosphate, Pyrophosphate, 0.2% Total 0.4% Total 8olids Solids 20 25 34
0 0 0 0
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tration decreases below the level a t which it is completely precipitated by the calcium. Figure 7 shows the p H values of various mixtures of phosphate and synthetic detergent, and in general is entirely comparable to the similar curves drawn for the system involving soap. ‘It may be noted that the minimum on the 0.2% pyrophosphate curve, exhibited by the soap-builder system, is not evidenced here with the data available. The various equilibria which were referred to previously are somewhat different here, since there is no hydrolysis of the detergent; hence the absence of a minimum in this case is in accord with the authors’ previous hypothesis. Figure 8, showing the detergency of the synthetic detergentphosphate mixtures, gives definite evidence of synergistic action in this case. The fact that tetrasodium pyrophosphate a t 0.270 total concentration produces a higher maximum than a t o.4y0 concentration, requires a n explanation. The point on the 0.2% curve corresponding t o 5oy0 builder shows the detergent Concentration t o be O.l%, and the detergency approximately 61. The corresponding point on the 0.4% curve will be at 75% builder, where the detergent concentration also is 0.1% but the detergency only 55. The difference, then, between these two points is the concentration of pyrophosphate, and it will be seen that the higher pyrophosphate concentration produces the lower level of detergency. It is possible t o obtain a rational explanation of this phenomenon by referring t o the customary theory regarding the action of electrolyte builders. Usually it is held that the improvement in detergency produced by builders is due t o the fact t h a t these electrolytes are effective in promoting micelle formation, and i t is granted generally that this micelle formation is related directly to detergency. Accepting this premise, i t follows t h a t micelle formation, and hence detergency, is related directly t o the total concentration of electrolytes present in the solution. I n the present case, it must be remembered that because hard water was used, the tetrasodium pyrophosphate which is added actually
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Figure 9. Foaming of Synthetio Detergent-Phosphate Builder Systems
BUILDER
SYSTEMS
0 10 25 50 75 90
The two hydrolysis reactions both will tend to increase the pH of the solution, as will the sequestering or precipitation of the calcium ion by pyrophosphate because this removal of the calcium will tend to reverse the precipitation of calcium stearate; thus the stearate ion concentration is increased and hence its hydrolysis. However, since the total solids concentration remains constant, the amount of stearate, and hence the extent of its hydrolysis, will decrease as the proportion of builder is increased. With all of these reactions proceeding as interdependent equilibria, it is extremely difficult to predict what the effect of changing the concentration of one of the ions would be on the pH. It appears at least possible, however, that the minimum effect observed may be explained on the hypothesis that in this region the total decrease in stearate ion concentration more than offsets the increase in hydroxyl ion concentration due t o the other competing reactions. Figure 6 shows the detergency of these same binary mixtures. Although trisodium phosphate and tetrasodium pyrophosphate both are somewhat effective in increasing the detergency a t 0.2% concentration, the maximum level reached is still quite low. A t .0.40/0, however, the effect is far more marked, and the maximum reached represents a high level of detergency. These data are in agreement with the previously reported findings of Harris et al. (6,11). This effect is clearly understandable in viewaf the fact that soaps such as sodium stearate are known to exhibit poor detergency in hard water because they are precipitated by the calcium. The large maximum on the 0.4% curve most probably is attributable not only t o the increased sequestering of calcium ions by the additional pyrophosphate, but also t o the fact t h a t the Concentration of stearate is greater than t h a t which can be completely precipitated by the calcium ions remaining. Table I, showing the foaming properties of these soap-builder mixtures, indicates that in water of this hardness not even the addition of builders will permit the soap t o produce an adequate foam. Some slight increase in foaming is exhibited by the addition of pyrophosphate a t 0.4% total concentration, but even this small improvement vanishes as soon as the total soap concen280
TABLE I. FOAMING OF SODIUM STMATE-PHOSPHATE
% Builder
Hydrolysis of the sodium stearate. Precipitation of stearate by calcium ion. Hydrolysis of the tetrasodium pyrophosphate. Sequestering of calcium ion by the pyrophosphate ion. Precipitation of calcium by the pyrophosphate.
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Figure 10. pH of Synthetic Detergent-Non hosphate Builder Systems (0.2% Total Solids7
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Figure 11. Detergency of Synthetic Detergent-Normphosphate Builder Systems (0.270 Total Solids]
Figure 12. Foaming of Synthetic Detergent-Nonphosphate Builder Systems (0.270 Total Solids)
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Figure 13. Foaming of System, Synthetic DetergentSodium Stearate-Tetrasodium Pyrophosphate (0.4Vo Total Solids)
performs two functions. First, as it is an electrolyte itself, it will tend t o promote micelle forniation; and secondly, by sequestering calcium ions it will tend effectively to remove electrolyte from the solution. These two essentially competing actions, therefore, may explain the apparent anomaly in the data given here by assuming that in water of this hardness the higher pyrophosphate concentration sequesters such a quantity of calcium ions that the total effective electrolyte concentration ip actually reduced. Figure 9, showing foaming of these mixtures, indicates that maxima are reached at low builder proportions-somewhere in the neighborhood of 257& Above this ratio, the quantity of synthetic detergent in the solution is evidently too small to produce effective foaming. While the present investigation is largely concerned with phosphate builders, specifically tetrasodium pyrophosphate because of its demonstrated lower p H and greater building efficiency, a brief study also was included on the effect of building synthetic detergent with nonphosphate electrolytes-such as sodium carbonate, sodium bicarbonate, borax, and sodium metasilicate. Figure 10 shows the pf1 values of such mixtures, and clearly demonstrates that only borax and sodium bicarbonate give reasonably low alkalinities. Figure I1 shows that none of the four nonphosphate electrolytes tested had appreciable synergistic effect with relation to detergency. Figurc 12 indicates that only sodium metmilicate appears to increase the foaming of svnthetic detergent, and even here the effect is not great.
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BO 70 DETERGENT
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Figure 14. Detergency of System, Synthetic Detergent-Sodium Stearate-Tetrasodium Pyrophosphate (0.4% Total Solids)
Ternary Mixtures.
On the basis of the data so far presented,
it was decided to employ tetrasodium pyrophosphate as the builder in the ternary systems to be examined in hard water, and t o conduct all tests at a total concentration of 0.4%. Figure 15 shows the foaming of such three-component systems, and indicates that the soap component actually has an inhibiting effect. This may be inferred from the steep slopes of the three wrves presentcd. These curves demonstrate also that the greatest quantity of foam is produced with the smallest soap and builder content. Figure 14, on the detergency of these same systems shows that a high level of detergency is maintained over a wide area when the soap in a soap-builder s3stem is replaccd progressively with synthetic detergent. The data indicate also that a higher level of detergency is obtained with 257, pyrophosphate than nilh 507,. \T7hen these data are plotted on triangular coordinates, as in Figure 15, the figures adjacent to the various points correspond to detergency values for mixtures of the corresponding composition. The shaded area indicates the region in which the level of detergency is 59 or greater; this is equal t o the detergency of sodium stearate in soft water. It is apparent tliltt such high detergency levels are okhainable with mixtures of widely differing compositions, ranging from zero to 65% synthetic detergent, 10 to 50% builder, and 18 to 80% soap. Two maxima appear on this graph: one a biliary 75 to 25 soap-builder mixture; and the other a ternary 20 t o 55 to 25 synthetic detergent-soap-builder composition. Figurc 16 shows the previously
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Figure 15. Detergency of System, Synthetic Detergent-Sodium Stearate-Tetrasodium Pyrophosphate (0.4% Total Solids)
Figure 16. Foaming of System, Synthetic Detergent-Sodium §tearate-Tetrasodium Pyrophosphate (0.4Yo Total Solids)
(A) Sodium stearate;
(A) Sodium stearate;
(B) tetrasodium pyrophosphate; synthetic detergent
(C)
recorded foam data similarly plotted on triangular coordinates. T h e curves represent compositions of approximately equal foaming ability, and i t will be seen that this foaming is greatest in those compositions containing only synthetic detergent and small amounts of builder. Finally, when the two previous graphs are combined (Figure 17) and the curve enclosing the area of detergency greater than 60 has been plotted, as well as two lines of equal foam height, one for 200 and one for 50, the upper shaded area then represents the region of maximum foam combined with maximum detergency, whereas the lower shaded area represents the region of minimum foam combined with maximum detergency. Both of these regions are of considerable importance from the practical point of view, since they indicate that the detergency of a synthetic detergent in hard water may be substantially increased by the addition of both soap and builder. Conversely, it is possible t o improve the usual built soaps, especially for use in hard-water areas, by incorporating a synthetic detergent. Thus, a wide variety of mixtures is potentially available for use either in powdered or bar form; these will exhibit marked advantages in foaming, detergency, and freedom from scum formation when employed in hard water. It is possible also to produce mixtures having a high detergency and little or no foam for use in washing machines and industrial washing operations, where a large volume of suds is often objectionable. ACKNOWLEDGMENT
The authors gratefully acknowledge the assistance of L. J. True and F. G. Lum in performing much of the experimental work. They are indebted also to the personnel of the Engineering Department of Standard Oil Company of California for the preparation of the graphs, and t o California Research Corporafor the photographs. LITERATURE CITED
Bacon, 0. C., and Smith, J. E., IND. ENG.CHEM.,40,2361 (1948). Bureau of Ships, U. S. Dept. of Navy, ad interim specification for detergent, 51D7 (Int.) (Nov. 1, 1942). Ibid., ad interim specification for soap, 51546 (Int.) (Dec. 1, 1943). Ibid., 51547 (Int.) (Oct. 1, 1945). Cobbs, W. W., Harris, J. C., and Eck, J. R., Oil & Soap, 17, 4 (1940).
(B) tetrasodium pyrophosphate4 synthetic detergent
(C)
C
A
8
A
Figure 17. Foaming and Detergency of System, Synthetic Detergent-Sodium §tearate-Tetrasodium Pyrophosphate (0.4% Total Solids) (A) Sodium stearate; (B) tetrasodium pyrophosphate; synthetio detergent
(C)
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