July, 1925
IL4-DUSTRIALA N D EXGIXEERIXG CHEMISTRY
685
For equilibrium vaporization, however, the equilibrium relations of the vapor phase with the liquid phase of any specified gasoline are completely expressed by a solid Phaserule diagram where one axis suffices to express the concentration of the two components by means of molar weights. If one fixed total concentration of a certain gasoline in a closed system a t a uniform temperature, the composition of each of the two phases is definite, there are two components, and a definite concentration of components in each phase corresponds to a definite molar weight.
shows the composition of the equilibrium solution and D' that of the gasoline vapor. D E and the corresponding line D'E' represent the dew point or "0 per cent condensed" curve of the gasoline, as shown in Figure 7. D E shows the slightly changing composition of the equilibrium solution and DIE' represents the constant composition of the vapor, which is the same as the original gasoline. A B and the corresponding line A'B' represent the vapor pressure of the gasoline or the "100 per cent condensed" CUNe as shown in ~i~~~~7.
Figure 15 shows such a diagram for Socony gasoline. The fac,e shown, A B D E , is the liquid area, and the hidden face, A'B'D'E , is the vapor area. The top surface A'ADD' is the same as Figure 3, which is a n isobar at 760 mm. pressure. The corresponding points D and D' represent the Depp6 end point, where D
Acknowledgment
This solid diagram Can be &ended to higher and lower temperatures and pressures and is capable of further analysis. The authors wish to express their appreciation to Lelalld Summers for his guidance, and to the Depp6 Motors Corporation at whose expense this research was undertaken.
Surface Tension as a Factor in the Priming of Steam Boilers' By E. B. Millard and T. E. Mattson MASSACHCSETTS IKSTITUTE OF
TECHNOLOGY, CAMBRIDGE,
hIA5S
of the liquid. Equating the EI'ERAL papers have The capillary rise method has been employed to decapillary forces to the downappeared recently beartermine at three temperatures the surface tension of ward force exerted by the ing upon the priming water, of sodium carbonate solution, and of two sammass of liquid and solving for of boiler water, among them ples of boiler water, one of which had caused serious y gives one by French2 in which is priming and the other did not prime. No very large the following s t a t e m e n t : differences in the surface tensions of these solutions rhdg "the whole problem is one of Y= 2 were found. The solution containing 17 mg, of soap surface tension, increased as per liter (1 grain per gallon) had a much lower surface from which it is seen that in the dissolved salts increase in tension than pure water at room temperature, but their a given capillary the capilconcentration, and complisurface tensions at 83.9" C. (183' F.) were practically lary rise is directly proporcated by operating conditions identical. Experiments with a small test boiler also tional to the surface tension and the physical character of failed to establish any connection between surface of the liquid. the water. * * * However, tension and priming. On account of its large dianything which will lower ameter, the capillary rise in the surface tension without creating complications will reduce foaming." This state- the larger arm is negligible; so that the height, h, which ment is in direct contradiction to the well-known foaming is measured by a cathetometer, is very nearly the true produced by soap in solution, and soap lowers the surface capillary rise. The surface tensions of a liquid a t two tenpion of a solution. Foulk3 has well described the existing different temperatures are not in exactly the same ratio confusion of the art and it need not be reviewed again here. as the capillary rises, owing to expansion of both the glass and liquid; but these errors are small, and are somewhat Capillary Rise Experiments counterbalancing, so that the final error is quite negligible for the present purpose. The present experiments were undertaken to determine APPARATUS-A constant temperature is maintained around what connection, if any, exists between the surface tension the capillary apparatus by the vapors of a suitable liquid, of boiler water and its tendency to prime. The capillary aniline or toluene, which is maintained in rapid ebullition rise method was found suitable for this purpose and the ap- in the apparatus shown in Figure 2. The rising vapors enparatus is substantially that described by Richards4 Fig- velop the capillary, and all condensate flows back to the lower ure 1 shows the capillary tube and its holder. The diameter part. Vapors not condensed by the air surrounding the of the capillary was determined before it was sealed (by weigh- vapor jacket are condensed in the steel condenser above and ing and measuring a mercury thread) to be 0.0496 cm. returned to the boiling liquid. A liquid that wets glass will rise in a capillary tube to such The apparatus and its heating jacket are arranged so that a height above a horizontal reference level that the surface they may be tilted. This is necessary because the lower tension is just offset by the weight of liquid in the capillary parts of the capillary apparatus reach the boiling point b e tube. If r is the radius of the tube and y the surface tension fore the upper regions do, resulting in temporary reflux in dynes per centimeter the surface tension in a capillary boiling. Part of the condensate formed thereby flows down will be 2nry. If the level of the meniscus in the capillary the capillary, forming a layer of distilled water on the solution tube is h cm. above the reference level, the weight, of liquid whose rise is sought. If this distillate is not mixed with the upheld by the capillary forces is rr2hdg, where d is the density rest of the solution, the capillary rise will be that for disReceived April 6, 1925 tilled water and not that of the solution under test. BubTHISJ O U R ~ A L ,15, 1239 (1923). bles, also, may be caught in the capillary. Both of these 3 I b i d , 16, 1121 (1924) troubles are overcome by the tilting. J. A m Chem. S O C 57, , 1656 (1918)
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
686
The holder which supports the capillary device and the condenser are so arranged that no cold condensate can flow on the capillary. The lower end of the condenser is provided with a short flexible wire which touches the jacket and conducts all t h e c o n d e n s a t e smoothly to its walls, whence it flows back to the lower part without coming in contact with the capillary device. PROCEDlJRE-NUmerOUS measurements have been made with this apparatus, and it has been found to work well. The maximum pressure which we have employed is about 12 atmospheres (1751bs. per sq. in., absolute), which is within the safe operating pressure for Pyrex glass of this size. Precautions were taken, however, to protect the observer with a heavy metal screen, outside of which is placed heavy wire-plate glass. Strong solutions of alkali (about 85 grams of sodium carbonate Der liter or 5000 grains Figure 1-Ca illary Tube andI per gailon) attack the -glass €&der at high temperatures, resulting in a slight enlargement of the capillary bore. This is not serious and can be corrected by making calibrations from time to time with distilled water. These experiments cover solutions of sodium carbonate, sodium carbonate with a small addition of soap, and two samples of boiler water from commercial power plants. Sample A came from a boiler which had given priming trouble at higher concentrations but which was giving no trouble at the concentration represented by the sample. Sample B came from a boiler which was giving serious trouble from priming. Several determinations were made of the capillary rise for each liquid and the average values are given in Table I. The individual measurements never varied among themselves by more than 1 or 2 per cent. Table I-Capillary Rise --Temperature
SOLUTION Water Sodium carbonate 17.1 grams/liter (!OOO grains/gallon) Sodium carbonate 85.5 grams/liter (5000grains/gailon) So8 and soda, 17.1 mg. soap and IF10 mg. NarCOa per liter (1 grain soap and 100 grains NanCOS per gallon) Sample A Sample B
25'C. (77' F.) 5.99
110OC. (230' F.) Cm. 4.90
5.93
4.75
4.12
...
4.20
...
3.91
4.83 4.77
4.00 4.02
Cm.
5.90 5.79
183" C. (361' F.) Cm.
3.93
RESULTS-The table shows that there is no connection between surface tension and priming. Samples A and B were not analyzed as their composition is beside the present point. One sample did prime and one did not; both contained sodium salts a t considerable concentrations and both contained suspended matter. Their surface tensions a t the higher temperatures, as measured from capillary rise, are practically identical and they do not differ materially from the values for water or sodium carbonate solutions. Experiments w i t h Test Boiler
Results obtained in the laboratory had failed to establish any connection between surface tension and priming, since solutions which supposedly primed badly (as Sample B )
Vol. 17, No. 7
gave about the same capillary rise as distilled water. Further tests were made with a small test boiler built to scale, containing about 45 kg. (100 pounds) of water and operated a t about 5 atmospheres (75 pounds) pressure. Heavy glass peep holes were installed in each end of the boiler. At one time when the boiler was running smoothly a considerable quantity of soda ash was added and very serious priming resulted. Slugs of water were thrown bhrough the steam pipe and something more than half of the water was thrown from the boiler. Analysis of the residual water showed 10.26 grams of soda ash per liter (600 grains per gallon). The capillary rise for this water was 3.74 cm. a t 183' C. (361" F.) which value is slightly lower than that for pure water. Water was added to the boiler, followed by a quantity of tallow soap sufficient to give a concentration of 35 to 50 mg. per liter (2 or 3 grains per gallon). Serious priming occurred again with great slugs of water passing out through the dry pipe. On the following day, when the boiler was running quietly, 35 mg. of soap per liter (2 grains per gallon) were added. The water level rose higher than the top of the peep hole, but no slugs of water passed into the dry pipe. After the boiler was blown out, and when it was again running steadily, a large quantity of soda ash was added. This caused the water to rise above the level of the peep hole but did not cause priming into the dry pipe. Thus, both soda ash and soap caused s e r i o u s priming on one day and neither soda ash nor soap caused priming on the following day. Since soda ash does not change the surface t e n s i o n of w a t e r materially and soap does change it, it was concluded that there was no connection between priming and surface tension. The variable which governs priming was not d i s c o v e r e d in this work* Flguri 2-Apparatus for Determining some c h a n g e was Relation between Surface Tension and made in the operation Priming of the boiler, as regards this unknown variable, between-one day and the next; but this variable does not seem closely connected with surface tension.
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Salesmen's Courses The College of the City of New York has concluded a course of lectures, given under the auspices of the Salesmen's Association, for the purpose of interesting the salesmen of our industry in the scientific side of their activity. Fifty-six men, representing twenty firms in the chemical industry, enrolled in the course, which consisted of lectures with exhibits anci,experiments followed by lantern slides and motion pictures. Chemistry in Industry" was used as the textbook for the course. The average attendance at each of the lectures was an indication of the siiccess of the undertaking. What has been done a t the City College can be done in other industrial centers. Such assistance as we can give the salesmen represents a good investment of our time and effort.
