T H E JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
628
the differences in surface tension between viscous and comparatively nonviscous oils were slight. It appears that it would be necessary to measure the surface tension exerted a t the interface between the oil and the metal, and not the surface tension of oil as determined against air, to determine the true relationship between surface tension and lubrication. The addition of 1 to 5 per cent of fatty acids, that is, commercial oleic acid, soy-bean fatty acid, and animal fatty acid, to Oklahoma oils increased the surface tension very slightly, that is, 0.1 to 0.8, but not enough to signify any great change in the physical properties of the oil.
Vol. 14, No. 7
It is probably true that a dissolved substance changes the surface tension of a nonvolatile solution; therefore, it is reasonable to assume that foreign substances or impurities may exert considerable influence on the surface tension. SUMMARY PRODUCT Crude. . . . . . . . . . . . . . . . . . Gasoline, .............. Naphtha. Kerosene.. . . . . . . . . . . . . . . Gas oil. ............... Lubricating o i l . . . . . . . . . . Wax distillate.
..............
..........
OF
TESTS
GRAVITY 36.4 45.0 56.3 - 62.4 46.7 - 55.2 40.2 42.4 35.9 14.7 27.1 27.6 - 33.2
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-
SURFACE TENSION AT 85O F. 28.8 31.2 24.4 25.8 26.3 29.2 30.7 31.2 33.1 36.0 - 37.5 33.6 36.2
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Automatic Carbon Dioxide Indicator for Flue Gas’ By R. B. MacMullin2 33 VERNON PLACE, BUFFALO, NEW YORK
The accompanying diagram depicts an apparatus for the continuous automatic analysis of a gas mixture for one constituent, such as carbon dioxide in flue gas. The apparatus can be made with bottles and glass tubing, and can be assembled compactly in a wooden case, 8 in. x 20 in. x 20 in., prooided with a window through which readings may be taken. The instrument is accurafe to 0.2 per cent carbon dioxide, and will record continuously for two days or more without need of refilling the scrubber or readjusting the zero point.
HE apparatus consists essentially of a dust trap, c,
T
a differential flowmeter, e, the readings of which indicate directly the percentage of carbon dioxide, a Friedrich’s spiral scrubber, IC, containing 25 per cent sodium hydroxide, a control capillary, m, a device for maintaining a constant pressure drop around m, a device, u, for maintainr ing constant pressure drop around the entire system, and a suction pump, y. The principle upon which the apparatus works is as follows: If a constant pressure drop be applied around the capillary m, air will be forced through it a t a constant rate. If air, instead of flue gas, be sucked into the apparatus, the rate through the flowmeter e will be the same as the constant rate through m. This causes the indicating liquids in the manometer of the flownieter to register 0 per cent carbon dioxide. If, now, gases containing carbon dioxide are sucked into the system, the caustic soda in the spiral scrubber causes enough additional gas to be sucked through e to make up the requisite standard rate of COz-free air through m. This increment of flow through e causes the indicating liquid in the manometer to be displaced by an amount corresponding to the per cent of carbon dioxide in the entering gas. DESCRIPTION OF APPARATUS DUST TRAP-An 8-oz. bot& filled loosely with cotton batting. Cock a admits flue gas and cock b, air to the system. FLOWMETER-The capillary tube e is about 15 cm. long and of about 1-mm. bore. The bulbs g1 and gz are taken from 50-cc. pipets and sealed to the manometric tubes hl and hz, of 3-mm. bore and 35-0111. length. The bulbs are filled half full of ethyl alcohol, colored with a dye. About 10 cc. of kerosene are placed in bulb 91. The dye is insoluble in kerosene and the boundary between the two liquids is distinct. The specific gravity of the alcohol used was 0.805 and that of the kerosene was 0.790. While the boundary remains in the cylindrical part of the bulb gl, 1 Received 2
March 2, 1922. Research Chemist, Mathieson Alkali Works, Niagara Falls, N. Y.
a 1-cm. movement of the boundary will represent a 1.61-cm. head of water around the capillary e. In order to make the boundary sink just into the manometer tube hl, a head of about 4 cm. alcohol or 3.2 cm. water is required. While the boundary is in the manometric arms a 1-cm. displacement corresponds to 0.805-0.790=0.015 cm. water. Thus, the movement of the boundary in the arm hl is 1.61/0.015 = 108 times as great as the movement in the bulb g1 for the same increment of pressure. The COz scale placed behind the manometer must be determined by calibration. While air is being sucked through the instrument, the rate through the capillary m is varied until the boundary just sinks into the arm h to a level arbitrarily chosen as zero. Gas mixtures of known carbon dioxide content are next admitted to the system, and after equilibrium has been reached the displacement p is measured on a millimeter scale. These values of p are plotted against per cent of carbon dioxide as indicated in Fig. 2. The values of p corresponding to even percentages of carbon dioxide are marked on a strip of white paper which is to be fastened permanently behind the manometric arms. If Vo is the standard rate of gas flow through m and V,, the rate through the flowmeter corresponding to x per cent carbon dioxide, the following relation holds : 100 (V,
- VO)
=
x.vz
Inasmuch as the deflection p is very nearly directly proportional to the increment of rate (V,--Vo) the spacing of the units on the GOz scale will be more liberal as the percentage of carbon dioxide increases. The size of capillary chosen (1 mm.) gives a rate for VO of about 100 cc. per min. Cotton should be stuffed into the arms fi and fz to reduce and dampen the vibrations of the boundary due to bubbling in the system. This also prevents evaporation of the liquids used in the manometer. SPIRAL SCRUBBER-AFriedrich’s spiral scrubber will give intimate contact between the gas and the liquid, and assure complete absorption of carbon dioxide. The scrubber will have to be recharged with fresh sodium hydroxide periodically. If the flue gas contains 10 per cent carbon dioxide, 200 cc. of 25 per cent sodium hydroxide will last 56 hrs. before being converted to sodium bicarbonate: Time =
1.285 X 25.5 X 2 X 22,300 X 0.90 = 55 hrs, 40 X 100 X 60 X 0.10
DEVICE FOR STANDARD RATE O F FLOW O F GAs-The Capillary m is somewhat finer than that in the flowmeter. It should give a pressure drop of at least 15 cm. water for a
THE JOURNAL OF IhTDUXTRIAL A N D ENGINEERING CHEMIXTRY
July, 1922
629
FIG. AUTOMATIC CARBON DIOXIDEINDICATOR FOR FLUEGAS
gas rate of 100 cc. per min. To facilitate selection and trial it is held in place by rubber nipples, as shown. The wide-mouthed bottle q should be a t least 13 em. in diameter; its capacity is immaterial. The tube p is 1.3 cm. in diameter and 35 em. long, and extends nearly to the bottom of the bottle. The 3-mm. tube o from the capillary extends to within about 18 em. of the bottom of the bottle. Tube t connects the upper end of p with the suction delrice ' u. Liquid may be forced in or out of bottle q by means of the leveling bottle s and the siphon r. Tube n connects the pressure end of the capillary with the gas space in bottle Q. Water may be used in q and s, but because of its tendency to evaporate and change the zero reading of the flowmeter, triacetin has been found better. It has an extremely low vapor pressure a t ordinary temperature, is quite mobile, and is xonhygroscopic. It has a density of 1.100. In operation, the suction on tube t is adjusted until the liquid level rises several centimeters above the outlet of tube o. The gas passing from o t o t must therefore bubble through a column of liquid 6 em. high. The pressure around capillary m is represented by the height of the liquid column y. This remains constant, even for minor fluctuations in 6, because of the large crosssectional area of the bottle q as compared to the tube p . For instance, a movement of 1 em. in p corresponds to a change in Y of (1.3/13)2=0.01 FIQ. 2
15 em. corresponds to The head is adjusted by means of the leveling bottle until the flowmeter reads zero for air. CONSTAKT SUCTION DEVICE--U is a hydrometer cylinder containing a several centimeter depth of mercury and about a change in head around m of 0.07 per cent.
10 em. of water, or, preferably, triacetin. The open tube v slides through the rubber gland wand dips into the mercury. The outlet tube cc connects with a small glass suction pump, y, actuated by water. The outlet tube on the pump should not be over 1 m. long, The pump is made to pull CL small stream of gas down through tube v and through the liquid in u. The upper end of v is connected to the dust trap by the tube d. By virtue of this connection, a constant head is maintained around the entire system. This head is represented by the depth to which tube v sinks into the mercury and triacetin. Thus $ cm. mercury and 4 cm. triacetin would 1.160 9 cm. water. The correspond to a head of 13.6 tube v is adjusted until the liquid level in the tube p rises several centimeters above the outlet of tube o as indicated. When the sample tube a is inserted in the chimney where the pressure is less than atmospheric, the seal in tube p might be broken, were it not for the equalizing effect of the by-pass d. The flowmeter does not respond immediately to a change in per cent carbon dioxide. In fact, a sudden increase in the per cent carbon dioxide is always accompanied by a preliminary deflection in the wrong direction. This is because carbon dioxide is less viscous than air, and causes a. decrement in pressure around the capillary e until this extra carbon dioxide begins to be absorbed by the sodium hydroxide in the scrubber. Two minutes should be allowed before reading, after a sudden change in the character of the gas sample.
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The Department of Chemistry of t h e University of Maine will conduct a School of Chemistry and a Pulp and Paper School from June 26 t o August 4, 1922. The work is designed t o meet the specific needs of premedical students, teachers of chemistry and science teachers who wish t o review the course in general chemistry or are preparing t o teach chemistry, students who desire t o begin or anticipate work in chemistry or make up deficiencies, students who are qualified t o take pulp and paper courses, and pulp and paper mill men with or without technical training who have had practical experience and desire t o gain a scientific understanding of important phases of pulp and paper manufacture and testing or phases of work with which they are unfamiliar. Special lectures o n pulp and paper topics, will be given.
