Melting Point Studies of Binary and Trinary Mixtures of Commercial Waxes J
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J. R. KOCH, GEORGE J. HABLE, AND LEWIS WRAEGELL Chemical Laboratories, Rlarquette University, Milwaulree, Wis.
Twelve aluminum pellets are fastened to the plate by means of the waxes to be studied. These pellets are small cylinders 5 mm. in diameter and 6 mm. long. They are slightly convex on one end, so that they will readily drop from the plate as soon as the wax becomes molten. In making a series of melting point determinations n-ith this apparatus, the wax mixtures are prepared on a large spot plate, w l i c h is placed on a water bath until all samples are molten. The brass melting point plate, together with the required number of aluminum pellets, is placed on an adjacent Tvater bath, and heated simultaneously with the spot plate. When the wax samples are completely melted, each pellet is transferred n-ith a forceps from the brass plate to one of the depressions in the spot plate, care being taken t,hat the convex side of each pellet is towards the bottom. When all the pellete have been transferred to the spot plate, the brass plate is placed horizontally on a ring clamped about 7.5 cm. ( 3 inches) above the spot plate. This keeps the plate at just the right temperature to prevent too rapid cooling of the wax, but at the same time ensures its solidification in a practical length of time. The pellets xith an adhering drop of wax mixture are now transferred from the spot plate to their positions beneath the corresponding numbers on the brass plate (Figure 2). Time for cooling should be allowed before the adjacent pellet is put in place. Vi'hen all the pellets are in place, the plate is allowed to cool for a few minutes, and then is transferred to the beaker containing the water and thermometer for the melting point determination (Figure 1). The actual determination of the melting points of the waxes used in fastening the pellets to the brass plate is made by recording the temperature at which the individual pellets drop from the brass plate.
ELTISG points of waxes or of wax mixtures vary somewhat, depending upon the method used for the determination. The true melting point methods, although they cover a Tyide range of manipulatiye art, do not differ widely in principle. They are based on tnro general principles: observation of the temperature a t which the opaque WVXY becomes transparent, or observation of the temperature a t which the v a x ceases to adhere to an object to which it has
FIGURE 1. APPARATCS been attached by melting and cooling. I n addition to these types of methods, too numerous to refer to specifically and differing in the results obtained only slightly, we have a class of determinations which are better named solidification point methods, depending for their values upon temperature readings a t constant time intervals from a thermometer immersed in a slowly cooling wax. Curves drawn from these data show flat points a t the solidification temperatures of the prime ingredients of the wax mixture. I n this paper we are concerned with the simpler melting point determinations.
Apparatus and RIethod For comparative melting points of a series of wax mixtures, it is very desirable that a number of related determinations be made a t one time. This ensures that the rate of heating, the amount of stirring or agitation, and all other factors shall be exactly the same for the entire series. To this end the apparatus illustrated in Figure 1 has been devised. The apparatus consists of a brass plate 12 X 3 cm. suspended in the center of a 2-liter beaker containing 1700 cc. of water.
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ANALYTICAL EDITION
Experimental Using the method described above, melting points of various commercial waxes were determined. Then in a single series the melting points of binary mixtures of various combinations of these were determined a t 10 per cent intervals of composition. Trinary mixtures were then prepared according to predetermined compositions, as explained below, and their melting points determined in series. Melting point curves of the binary wax mixtures are to be Sound in the three narrow graphs surrounding each of the triangular graphs. The triangular graphs, of course, represent all possible trinary mixtures of the waxes indicated. Since only compositions can be plotted, a single curve connects all mixtures melting a t one specific temperature. The melting point in degrees Centigrade for each curve is indicated thereon. I n general, a curve is drawn for every 2.5" rise in melting point, and the curves then may be compared to the altitude lines on a contour map. Each apex of the triangle represents 100 per cent of the wax indicated, and also 100 per cent of the indicated wax for the binary graph adjoining. An inspection of the curves will make this evident. Each side of the triangle represents all binary mixtures of t h e two waxes indicated a t the ends of the line. From the binary melting point data we may select binary mixtures melting at, let us say, 62.5", 65", 67.5", TO", and 72.5' C . By drawing a line on the triangular graph between two sets of binaries that have the same melting point we obtain suggested compositions of trinary mixtures for that melting point. Compositions are chosen a t uniform intervals over the length of the line and the melting points of the trinary mixtures determined. For a very short line one trinary mixture is sufficient, while for a long line 4 or 5 trinary mixtures are used. A number of checks were made on each mixture and checks
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within 0.5" C. R-ere required. I n no case was i t found that the suggested composition failed to have the required melting point n-ithin the limits of experimental error.
Results and Conclusions The complete picture of the most interesting and valuable results obtained in this study is shown here graphically. A careful study of these graphs will materially assist one in any investigation of the characteristics of the waxes used in these melting point studies. Knowing the qualitative composition of a trinary mixture of waxes, the melting point of this mixture will enable one by use of these graphs to determine the approximate quantitative composition of the mixture with a minimum of other data. Likewise by use of the graphs, mixtures of waxes of any desired melting point can readily be prepared. The practical usefulness of these graphs to anyone pursuing studies of waxes far surpasses any theoretical discussion which might be set down here based on the results. Severtheless some of the outstanding characteristics evidenced by certain waxes are worthy of comment. It will perhaps seem striking a t first sight that the isothermals actually are straight lines within the limits of experimental error. This substantiates the idea that wax mixtures are true mixtures and that new chemical compounds are not formed. Because of the comparative chemical inertness of the esters and hydrocarbons making up most waxes, this is to be expected. The effectiveness of small amounts of carnauba in raising the melting points of individual or mixed waxes is noted in Figure 3 (left and center). This is shown in the triangular graphs by the packing of the isothermal lines near the bottom of the graphs. I n these two graphs, the contour line conception of the isothermals can be best appreciated, and it is not difficult to visualize the third dimension which these lines
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FIGURE 3. ~ T E L T I N Q POISTGRAPHS
FIGURE 4. MELTINGPOINTGRAPHS
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FIGURE 5. MELTINGPOINTGRAPHS h
FIGURE 6. MELTINGPOINTGRAPHS portray, especially by using the adjacent binary graphs as Droiile mam. * The on(y other wax approaching carnauba in its effectiveness in quick melting point rise is Chinese insect wax, whose effect on beeswax is shown in Figure 6. The fact that the isothermal lines are not parallel in any instance quickly establishes the fact that the effect of any in-
dividual wax on the melting points of two other waxes is never proportionally the same, but is specific. This is also shown by the dissimilarity in the shape of the various binary mixture curves. A striking example of the effectiveness of each of two waxes in altering the melting point of the other when present in small quantities is shown in the binary curve for beeswax and candelilla (Figure 6). A diametrically opposite effect is shown in the case of candelilla and Chinese insect wax on the same graph. Many other equally ++, interesting characteristics of the individual waxes could be pointed out. Since the results produced here graphically represent a large amount of careful and tedious work, it is hoped that these graphs may- prove to be a useful tool to many readers. -
Acknowledgment This paper was prepared with the advice and assistance of
J. Vernon Steinle, S. C. Johnson & Son, Inc., Racine, Wis. RECEIVED
November 22, 1937,
A One-Piece Standard Pipe Tee Piezometer Ring FRANK C. VILBRANDT, Virginia Polytechnic Institute, Blacksburg, Va.
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HE static pressure of a liquid flowing in a pipe line can be measured by a manometer. Connection of the manometer to the pipe ordinarily involves the installation of a ring piezometer or the tapping of the pipe. A ring piezometer, a circumferential ring manifold with four or more holes, is supposed to give a n average static pressure, while the single tapping gives a reading for only the tapped point. But the ring piezometer is costly of construction and not easy to attach; often it is built in with the equipment, as in the case of the Venturi meter. To overcome the complications and costliness of the ring piezometer, Baker and Komich (1) substitute a circumferential slot for the numerous tapped holes, using a single tapping of the pipe. This modified ring requires fittings totaling five threaded joints, one of which is through the thin curved wall of the nipple where the lead-off tap is located. A simpler arrangement with but three joints and a standard
TO MANOMETER
FLUID IN M O T I O N
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FIGURE 1. STANDARD TWO-INCH REDUCINGTEE PIEZOMETER RING
