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INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 10, NO. 3
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 characteristics of the indi++, interesting vidual 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.
T
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
ANALYTICAL EDITION
MARCH 15, 1938
outlet instead of a tapping through the pipe wall can be used. Figure 1 shows specifications for a standard 2-inch piping ring, but the same order of magnitude of clearances is obtained with other pipe tees and piping. The static flow connection from the flow pipe to the manometer consists of a n outlet reducing tee. The tee is of the same size as the flow pipe with a nominal 0.25- or 0.125-inch pipe outlet. One end of the flow pipe is screwed into the tee, so that it just emerges into the inner chamber of the tee. The other end is threaded to a length that will allow it to be screwed onto the tee, and t o approach the other pipe to within 0.05inch. The threads on the longer threaded pipe are removed by machining or filing,
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leaving only those threads that are engaged by the female threads of the tee. Thus a static fluid chamber is provided between the interior aTalls of the tee and the outer walls of the penetrating pipe. This annular chamber connects by means of the slot to the flow pipe and by means of the reducing outlet to the manometer.
Literature Cited (1) Raker, C. P., and Komich, A. J., 9, 533 (1937).
ISD. ESG. (:HEM., Anal. Ed
RECEIVSDSovember 30, 1937.
High-Vacuum Gas-Analysis Apparatus EDWARD C. WARD, Alco Products Incorporated, New York, N. Y.
A simple method is described for the accurate fractional analysis of light hydrocarbons, using high vacuum in the order of 1 m m . of mercury absolute. The separation is accomplished i n a condenser train with temperatures controlled by liquid air. Unusual accuracy is obtained because of the high vapor pressure
T
HE conventional type of apparatus for the separation of a low-boiling hydrocarbon mixture into its individual components employs a fractionating column usually operating at pressures ranging from atmospheric down to 100 mm. mercury absolute. This type of apparatus has found wide acceptance in the oil and gas industries and is adaptable to the analysis of a wide range of gaseous and low-boiling hydrocarbon mixtures. Another type of apparatus has been used by this laboratory for several years and is believed to offer certain advantages in the analysis of hydrocarbon gases and vapors. Fractionation is effected in this apparatus at low pressures by means of a series of simultaneous partial distillations and condensations through a series of tubes, maintaining a temperature gradient from tube to tube. TABLE I. VAPORPRESSURE RATIOS (Working under normal pressures) High-Vacuum Standard Separation Apparatus Column Methane-ethane 2000 480 Ethane-pro ane 100 13 P r opane-isot ut ane 12 4.5 Isobutane-n-butane 5 2 n-Butane-isopentane 15 3.5
Some of the advantages claimed for this procedure are the following: 1. A small gaseous sample, nominally 150 cc., is sufficient for a complete analysis, thereby eliminating the use of expensive high-pressure bombs or large bulky low-pressure containers. 2. Traces of material at the ends of the distillation are determined with unusual precision-for example, small amounts of heavy hydrocarbons in absorber residue gases may be determined to 0.02 per cent and light hydrocarbons in stabilizer residues may be detected within 0.1 per cent based on the original sample. 3. Supplementary tests such as oxygen determination, bromination of unsaturates, slow combustions, etc., may be made on gas fractions without removing the sample from the apparatus. 4. The time required for an analysis is only about 2.5 hours.
ratio of the components at the point of separation. Individual components are determined within 0.02 to 0.1 per cent, depending on their concentration i n the original sample. Results obtained by this method have been used for equipment design and plant control over a period of years. The ease of separation of two hydrocarbons varies directly with the ratio of their vapor pressures a t the particular temperature employed. This ratio increases materially as the temperature is reduced (Table I); therefore, it is highly desirable to effect a separation a t the low temperatures attainable under high vacuums. For several reasons it is difficult to operate the usual form of low-temperature column a t pressures in the order of 1 mm. of mercury. The vapor capacity of small diameter columns a t 1 mm. of mercury or less is markedly reduced, so that the time required to complete an analysis is greatly extended. Small fluctuations in pressures at these high vacuums greatly affect the fractionation and accuracy of the results. Shepard and Porter ( I ) employed a high-vacuum apparatus for the analytical separation of gaseous hydrocarbons by a series of fractional condensations and distillations through a condenser train without the use of reflux. The apparatus described in this article depends essentially upon the same principle as the Shepard and Porter method, but is of different design, requires less time per analysis, and gives results which are thought to be of the same precision.
Apparatus The separations are effected a t a pressure of less than 1mm. absolute in a train of four condenser tubes held accurately to temperature by the procedure described below, using liquid air as the cooling agent. The apparatus is constructed entirely of Pyrex glass with all fused joints except in the Orsat section where substantially atmospheric pressures are used and danger of leaks is small. It consists (Figure 1) essentially of a condenser train for the lowtemperature separation of the hydrocarbons, an internal highvacuum pumping system for transferring sample and fractions, a McLeod gage for determining the pressure in the system, a constant-volume buret for measuring both sample and fractions, drying tubes, and an Orsat system for running sup lementary tests. As the apparatus does not work well with iquid samples, a
