Myers' Demulsification Test for Bituminous Emulsions PRESTON R. SMITH,The Barber Asphalt Company, Maurer, N . J . T H E METHOD for performing the demulsiIt is a t once obvious that the ITHIN the past year a Jication test f o r bituminous emulsions is diss t r e n g t h of the calcium chlonew m e t h o d for deride solution must be precisely t e r m i n i n g the stacussed. I t iS pointed Out lhat the standard c o n t r o l l e d , The bestmethod bility of bituminous emulsions calcium chloride shodd be made preciselyand of preparing a standard calcium has been suggested by Joseph E. Myers, chief chemist of the fhat the temperature of the emulsion and the chlorideasohtionis that used by New Yorlc State Highway Decalcium chloride solution should be controlled the A m e r i c a n P u b l i c Health partmerat. This test has been during the test. A lemperature of 250 1 0 C. Association. found to be Of is recommended, and a sieve made of wire that Preparethe 0.02 ~ ~ s t a n d a ~ d value in classifying and studying calcium chloride solution by diswill not be attacked by alkali must be used. such emulsions. ~1~~ m e t h o d solving 1.0008 grams of dry calcium carbonate or pure calcite of conducting the test is here in the least possible excess of dilute hydrochloride acid, taking given (2>3). care to avoid loss by spattering. Remove the excess of acid One hundred grams of emulsified asphalt are placed in a tared by several evaporations to dryness and make up to 1liter. 600-cc. glass beaker and 35 cc. of 0.02 N calcium chloride solution In most cases the per cent demulsification is a function of are added during a period of approximately 2 minutes, being stirred with a lass rod. The contents of the beaker are then the temperature. With certain emulsions the effect of drained througgh a No. 14 sieve, and the unbroken emulsified temperature is negligible, whereas with others it is very asphalt in the beaker and on the rod is rinsed through the sieve with distilled water until there is no appreciable discoloration marked. This is brought out by reference to Table I. In of the rinsing water. The beaker, rod, and sieve are then dried making these tests, both the emulsion and the calcium in an oven at 163" C. (325" F.) for 2 hours and weighed. The chloride solution were brought to the indicated temperature percentage of asphalt residue deposited in the beaker and on the which was maintained during the mixing of the two. It is rod and sieve is taken to be the difference between the weight of the beaker, rod, and sieve after drying, and their tared weight apparent that the temperature must be controlled with considerable accuracy, and it is recommended that 25" * 1O C. determined at the beginning-of the test. be used. This test is founded on the tendency of calcium chloride to TESTS TABLE I. RESULTSOF DEMULSIFICATION break an oil-in-water emulsion by the formation of an insoluble calcium soap from the alkali soap used as the emulsifier. EMULSION AT 20° C . AT 2 5 O C. AT 30' C. I n practice it is used to distinguish between two classes of emulsions: the quick-breaking type of bituminous emulsion which shows a high value in this test, and the slow-breaking type of bituminous emulsion which shows little or no demulsiTEST 86-02 fication. It is assumed that this test is indicative of the AT 15' C. AT 2 5 O C . AT 3 5 O C . 6 1.6 7.4 14.8 rapidity with which an emulsion will break when in contact 6 Trace 1.6 13.2 with a given type of mineral aggregate. Insufficient work That the test involves factors other than the formation of has been done as yet to show this connection in all cases. At the present time caution must be exercised in interpreting calcium soap is suggested by the rather pronounced temperature effect. If the reactions taking place were simple, it the results in highway work. This test has been modified in practice by changing the might be expected that some connection could be shown amount and strength of calcium chloride solution used. For between the demulsification value and the quantity of calcium ready reference these various modifications are designated chloride used. For example, it might be expected that 35 cc. of 0.02 N calcium chloride would give the same result that as follows: would be obtained with 70 cc. of 0.01 N calcium chloride. 35-02, 35 cc. of 0.02 N CaCln 50-01, 50 cc. of 0.01 N CaCl2 That this is not the case is brought out in Table 11. Further 50-02, 50 cc. of 0.02 N CaCls study of the mechanism involved must be made before any 50-10, 50 cc. of 0.10 N CaCl2 definite conclusions can be reached. It seems probable that 70-01, 70 cc. of 0.01 N CaClz dilution has some effect on the demulsification observed. It These various modifications used by different laboratories should be understood that all of the emulsions considered have been devised to cover adequately the entire range of herein show perfect miscibility in water ( I ) . bituminous emulsions. It is perhaps unnecessary to retain TABLE 11. EFFECT OF DILUTION ON DEMULSIFICATION all of these modifications. At the present time bituminous (All determination8 at 25O C.) emulsions are made which show values of from 0 to 100 per EMWLBION TEST35-02 TEST70-01 TEST50-01 TEST60-10 cent demulsification by the original test. The range of useful% % % % ness of the test has been increased by altering the amount and 1.4 ... 3 . 7 ... concentration of the calcium chloride solution. 1.1
PRECAUTIONS In determining the per cent demulsification of a bituminous emulsion, it has been found that in order to obtain reproducible results it is necessary to observe certain precautions not mentioned in the original method.
...
Many bituminous emulsions, especially those made with a strongly alkaline emulsifier, will attack brass, solder, etc. This can be easily demonstrated by pouring a strongly alkaline 105
ANALYTICAL EDITION
106
bituminous emulsion through a brass sieve on which an appreciable amount of separated asphalt will be collected. The same emulsion when poured through an iron screen of the same mesh will show no separation of asphalt. A satisfactory screen cgm be made by bending a piece of iron wire cloth (12 mesh; 0.028-inch diameter wire; 0.055-inch opening; this corresponds to a No. 14 standard test sieve) over the end of a cylindrical or spherical block forming a basket. A convenient size is about 3 or 4 inches (7.6 or 10.1 om.) in diameter and 1 to 2 inches (2.5 or 5.0 em.) deep. A piece of heavy iron wire can be caught through the upper edge to serve as a handle. No solder should be used. Repeated tests have failed to show any difference in the results when the emulsion and calcium chloride are allowed to
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stand for a considerable length of time or the asphalt is drained at once through the screen. Emulsions which show high percentages of demulsification frequently separate the asphalt in the form of a large lump which is quite likely to entrain unbroken emulsion. The calcium chloride should be added slowly with vigorous stirring in order to keep excessively large lumps of separated asphalt from forming.
LITERATURE CITED (1) Am. SOC.Testing Materials, Tentative Method of Testing Bituminous Emulsions, D-244-28T (1928). (2) MoKesson, C. L., Am, SOC.Testing Materials, Preprint 84 (1931). (3) Myers, J. E., private correspondence. July R~CBIV E ~31, 1931.
A New Jelly-Strength Tester C; R. FELLERS AND J. A. CLAGUE, Massachusetts State College, Amherst, Mass.
M
EASUREMENT of jelly strength is of importance not only in the study of pectin but also in the manufacture of fruit and artificial jellies. The standardization of jellies and similar products with respect to consistency and jelIy strength is much to be desired. Paine ('7) in 1922 called attention to the need of a satisfactory method of measuring the jelly strength. Since that time several jelly-strength testers have been described by Sucharipa (9), Baker ( I ) , and Tarr (IO). Fellers and Griffiths (4) have shown that the Bloom gelometer (S), originally adapted for testing gelatin (8), could be used to measure the jelly strength of fruit jellies and similar products. But these instruments are either expensive, non-mobile, or of complex construction. Their use is limited almost entirely to the laboratory.
FIGURE1. DETAIL OF JELLY-STRENGTH TESTER
To overcome such difficulties and to supply the need for a simple tester of more general utility, the present instrument was devised. It operates on a principle similar to that utilized in several pressure testers which have been recently devised by Magness and Taylor (6), and Blake (d), for determining the maturity of pears, apples, peaches, etc. As illustrated in Figure 1, a detachable plunger, A , is attached to a metal rod, B, which runs through a hollow metal cylinder, C. Bearings, D, for the rod are provided a t either end of the cylinder. Within the hollow cylinder a spring is attached to the metal rod a t one end and to the bottom bearing at) the other, 'ebd. This- spring provides the necessary tension. An eyelet, E , attached to the plunger rod projects through a slot, F , in the cylinder and travels back and forth with the rod. On the outside of the cylinder the eyelet encircles a small rod, G, running parallel to the plunger rod. There is a leather washer, H , on this small rod which is pushed by the eyelet and marks the highest point reached by the latter. A scale registering the tension of the spring in
grams is stamped on the metal cylinder and the pressure necessary to break the jelly layer may be read directly. To eliminate the effect of the weight of the instrument tests must be made with the tester held horizontally, as shown in Figure 2. The plunger is placed on the surface or layer of the jelly to be tested and pressure is slowly applied until the surface is broken, when the plunger springs back to its original position. The leather washer marks the maximum pressure reached, which is read directly in grams from the scale. Because of the ease of making the pressure tests, fully eight or ten measurements may be made in a minute. Results of measurements made to test the accuracy of the instrument are shown in Table I. Apple jelly and strained cranberry sauce were prepared in quantity and poured while hot into a large number of 2-ounce straight-sided glass jars, These were paraffined to prevent surface evaporation and tested for jelly strength the following day. Several of the samples of cranberry sauce examined were from tin cans holding 21 ounces. The tests were made by cutting the jelly mass in two and determining the jelly strength of both cut surfaces. In general, the cut surface of a jelly gave more reliable pressure measurements than the outer surfaces-i. e., the top or bottom. In preparing the jellies a series was purposely included extending from soft to very firm consistency. The probable error was calculated by use of the formula (6):
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P. E. = 0.6745
4%
where P. E. is the probable error, d. the deviation from the arithmetic mean, and N the number of determinations.
FIGURE 2. INSTRUMENT IN OPERATION '
From Table I, the average per cent deviation from the mean in a large number of determinations is 3.51 to 4.7, indicating a reasonable accuracy for the instrument.
