January, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
In another test two samples of stock water containing 5.0 p. p. m. of fluorides were mixed for 30 minutes with 1.5 and 50 p. p. m., respectively, of fresh powdered activated alumina. The waters were filtered and found to contain 4.2 and 2.0 p. p. m. of fluorides, respectively. The activated alumina settled rapidly; hence the waters could have been decanted instead of filtered from the alumina. BAUXITE. A bauxite (commercial grade) contact filter operated in the same manner as the activated alumina filter gave small removal of fluorides. SILICA GEL,SODlUM SILICATE, A44ND F E R R ~ SALTS C A contact filter containing 498 grams of silica gel reduced the first 6 liters of a 5.0 p. pam. fluoride water to 4.0 p. p. m. (filtering rate, 350 cc. per minute). Treatment of waters with sodium silicate (256 p. p. m.) and aluminum sulfate or sodium aluminate gave removals of less magnitude than that given by the same treatment without the sodium silicate. It is known that the ferric fluoride complex is only slightly ionized. Therefore there was a chance that fluorides might be removed by this coagulant. Treatments of 2 to 5 grains per gallon (34 to 85 p. p. m.) on waters containing from 1.8 t o 5.0 p. p. m. of fluorides a t a pH of 7.2 gave small removals. When the treatment was accompanied by 10 to 20 grains per gallon of lime (170 to 340 p. p. ma),waters containing 1.8 and 5.0 p. p. m. of fluorides were reduced to 1.6 and 4.7 p. p. m., respectively.
71
LIME TREATMENT Treatment of stock waters with sufficient calcium hydroxide to cause precipitation of the carbonate and magnesium hardness and produce a phenolphthalein alkalinity which was equal to or slightly greater than half the total, brought about co-precipitation of part of the fluorides present. I n one test a water containing 5.0 p, p. m. of fluorides was reduced to 3.0 p. p. m. while another containing 3.0 p. p. m. was reduced to 2.1 p. p. m. ACKNOWLEDGMENT The activated alumina, silica gel, and synthetic zeolite used in this investigation were furnished through the courtesy of International Filter Company, Chicago, Ill. LITERATURE CITED (1) Boissevan. Colorado Medicine (April, 1933). (2) Boruff and Abbott, IND.ENO.CHEM.,Anal. Ed., 5 , 236 (1933). (3) Buswell, “Chemistry of Water and Sewage Treatment,” p. 164, Chemical Catalog, 1928. (4) Dean, J. Am. Dental Assoc., 20, 319 (1933). ( 5 ) Dean, Pub. Health Repts., 48, 703 (1933). (6) Sebrell, Dean, Elvove, and Breaux, Ibid., 48, 437 (1933). (7) Smith, Lantz, and Smith, Ariz. Expt. Sta., Tech. Bull. 32, 253 (1931). (8) Smith and Smith, Ibid., 43, 213 (1932).
RECEIVED September 12, 1933. Presented before the Division of Water, Sewage, and Sanitation Chemistry st the 86th Meeting of the American Chemical Society, Chicago, Ill., September 10 to 15, 1933.
Effect of Water Vapor on Ignition Temperatures of Methane-Air Mixtures G. W. JONES
I
AND
HENRY SEAMAN, U. S. Bureau of Mines Experiment Station, Pittsburgh, Pa.
If the presence of water vapor Water vapor, in amounts above 5 mm. vapor has an appreciable effect on the the Bureau of Mines for deraisesthe ignition temperatures ease of ignition of natural gastermining the permissibility of methane-air mixtures. The maximum inof explosives, natural gas-air air mixtures by explosives when crease in ignition temperature is 11’ and ocmixturesof uncontrolled humidithe hot products of detonation ties -axe used. Objections have curs f o r a saturated mixture containing approxiare discharged into the mixtures, then, since natural gas consists been raised to these tests on the mately 4 per cent methane. Water vapor has no largely of methane, differences grounds that the moisture conappreciableeffect upon the lag on ignition f o r tent of the mixtures may affect should be found in the ignition methane-air mixfures. the ease of ignition which is detemperature of methane-air mixtermined largely by the ignition tures, or in the lag a t the ignition temperature and the lag a t the ignition temperature. The temperatures, when the percentages of water vapor present ignition temperature may be defmed as that temperature a t in methane-air mixtures are changed. Tests are made with which rapid combustion becomes independent of external s u p this end in view. plies of heat. The lag is the time required a t the given temPREVIOUS WORKON RELATIONOF MOISTURE TO IGNITION perature to cause ignition of the mixture. TENPERATURES Ignition temperatures are affected by a number of variables; the most important, in addition to lag, are the percentage Although the specific effect of small traces of water vapor of combustible in the mixture, the oxygen concentration, the on gaseous reactions has been known since Dixon’s historic size and form of the apparatus used and the material of which report in 1880 ( 2 ) , few determinations of the effect of water it is composed, the pressure on the mixture when ignition vapor on ignition temperatures have been reported. Prettre occurs, and the presence of catalysts and small amounts of and Laffitte (4) studied the effects of “burnt residual gases” impurities in the mixtures. on the ignition temperatures of carbon monoxide. They By using an apparatus of a definite size and structure, and found that the ignition temperature of one mixture was lowan oxygen supply of constant proportions (normal air), by ered 30’ C. by 7.6 per cent of water vapor. This corresponds conducting the experiments a t atmospheric pressures, and with the reports of Bone and Weston (1) who found that the by eliminating impurities in the mixtures, the effect of water ignitibility by condenser discharge sparks of a 2CO 0 2 mixvapor on the ignition temperature of a combustible-air mis- ture rapidly diminishes as the water vapor is removed, the ture can be determined. minimum spark energy required to ignite it increasing until X T H E gallery tests used by
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 26, No. 1
EXPERIMENTAL RESULTS Tests were made using a dry gas, gases of approximately 20 per cent and 50 per cent relative humidity a t room temperature, and a gas saturated a t room temperature. In Figure 1 are shown the ignition temperatures for these mixtures. The differences between the ignition temperatures for the dry and saturated gases vary somewhat with the composition, reaching a maximum of 11 C. for a mixture containing 4 per cent of methane. The minimum ignition temperature for saturated gas occurs in mixtures with 5.5 to 6.0 per cent of methane; the dry gas has its minimum ignition temperature in mixtures containing 4.5 to 5.0 per cent of methane. Results for the mixtures of 20 per cent humidity seem to coincide with those for the dry gas, while the curve for the mixtures of 50 per cent humidity lies between the dry and the saturated mixtures, although somewhat closer to the dry gas. The effect of amounts of water vapor less than 20 per cent of saturation is too slight to be decided by these tests. In Figure 2 are shown the lags on ignition for the various mixtures used. Although the values for each mixture varied considerably among themselves, there appears to be no tendency for water vapor to affect the lag to any appreciable amount. Table I gives a summary of the data obtained, including the calculated water-vapor pressures. O
1
6MI
I
1
1
1
1
1
I
I
I
" 12
PERCENT METHANE BY VOLUME, DRY BAS2819
FIGURE1. IGNITIONTEMPERATURES OF METHANE-AIR MIXTURESCONTAINING VARIOUSPERCENTAGES OF WATERVAPOR with a mixture dried by calcium chloride it becomes twenty to thirty times as great as that required to ignite the same mixture when saturated with water vapor a t 15" C. The influence of water vapor on ignition lag was studied by Taffanel and Le Floch (5) who found that 10 to 20 per cent of water vapor produced no systematic change in the lag for methaneair mixtures.
EXPERIMENTAL METHOD The apparatus and method used are the same as described by Jones, Seaman, and Kennedy (3). The ignition takes place in a cylindrical quartz bulb of 131 cc. capacity, electrically heated. The bulb may be connected independently to a Hyvac pump, to a 19-liter bottle containing the mixture, or to the atmosphere through a water seal. Temperatures of the bulb are determined by means of a thermocouple centrally placed on the external surface and connected to a potentiometer. Between each test the bulb is evacuated and filled twice with nitrogen.
TABLEI. IGNITIOX TEMPERATURES OF METHANE-AIR MIXTURES
WATER IGNI- LAGO N VAPOR TION IGNITEET METHANE PRESSURE TEMP. TION M m . Hg ' C. Seconds 4.3 0 650 12 6.2 651 12 0 0 7.9 656 11 0 9.2 660 10 4.5 648 0 14 3.9 649 0 13 7 8
9
lo 11 12
I 0
l
1 2
1
l 4
1
I 6
I
I 8
I
l 10
I
I
13 14 15 16 17 18 19 20 21 22 23
TEMP. OF
TEST
c.
26.0 27.0 24.0 24.0 25.0 26.0
4.8 6.25 8.9
5.0 5.0 5.5
648 651 658
11 14 9
24.5 24.5 25.7
4.8 6.5 8.9
12.4 11.2 10.3
652 654 661
13 12 9.5
26.0 24.3 23.0
4.0 5.35 7.6 9.9 11.6 9.6 4.15 4.9 7.2 5.7 3.8
25.0 26.5 25.0 22.15 22.15 22.15 22.15 22.15 22.15 22.15 22.15
661 659 661 671 678 668 659 668 659 657 661
11
11 8 6 9 10 13 11 11.5 10
26.0 27.0 26.0 24.0 24.0 24.0 24.0 24.0 24.9 24.0 24.0
iz
12
PERCENT METHANE BY VOLUME, DRY BASIS
FIGURE2. VARIATION OF LAG AT IGNITION TEMPERATURE WITH CHANGEIN COMPOSITION AND HUNIDITYOF MIXTURE
LITERATURE CITED (1) Bone, W. A,, and Weston, F. R., Proc. Roy Sot. (London), llOA,
615 (1926). (2) Dixon, H. B., Brit. Assoc. Repts., 1880, 603.
(3) Jones, G. W., Seaman, H., and Kennedy, R. E., IND. ENQ. CHEM.,25, 1283 (1933). (4) Prettre, M., and Laffitte, P., Compt. rend., 188, 1403 (1929). (5) Taffanel, J., and Le Floch, G., Ibid., 156, 1544 (1913).
The mixtures were made in a 19-liter bottle containing 500 grams of a sulfuric acid-water mixture calculated to give the desired humidity at 24" C. The dr mixture was made by passing the air through concentrated sulLic acid and soda lime. For the wet tests the bottle, containing 500 cc. of water, was shaken at irregular intervals over a period of approximately 3 hours. The lag on ignition was determined by means of a stop watch.
U. S. Bureau of Mines.
NETHERLANDS SUPERPHOSPHATE INDUSTRY.There are three important companies engaged in the manufacture of superphosphate in the Netherlands. The United Chemical Works and the Amsterdam Superphosphate Works, which operate for joint account, have an annual capacity of 400 000 to 500,000 metric tons of fertilizers (principally superphosphates). The other imortant producer is the First Netherland Cooperative Fertilizer borks, the only cooperative superphosphate producer in the country. Its fertilizer plant is reported to have an annual capacity of 200,000 metric tons, and it produced during the year ended April 30, 1933, about 178,000 tons, an increase of 11,000
tons over the previous year. The organization has about 7000 members, but only 29,000 tons of product were delivered to them during the past year. Those members who had failed to buy the quantity of superphosphate required by the articles of association had to pay a penalty of 1 guilder a metric ton, this being the difference in price charged to members and the average price charged to nonmembers for the fiscal year under review. Although the total sales of Netherlands superphosphate declined in the domestic and export markets, the cooperative plant succeeded in gaining a larger portion of the home market and increased its export tonnage t o certain countries.
RECEIVEDAugust 11, 1933. Published by permission of the Director, (Not subject t o copyright.)
